Merge pull request #1220 from anuragagarwal561994/java-11

Java 11 (patterns with m)

marker/src/main/java/App.java

@@ -46,17 +46,18 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
+    final var logger = LoggerFactory.getLogger(App.class);
+    var guard = new Guard();
+    var thief = new Thief();
 
-    final Logger logger = LoggerFactory.getLogger(App.class);
+    //noinspection ConstantConditions
-    Guard guard = new Guard();
-    Thief thief = new Thief();
-
     if (guard instanceof Permission) {
       guard.enter();
     } else {
       logger.info("You have no permission to enter, please leave this area");
     }
 
+    //noinspection ConstantConditions
     if (thief instanceof Permission) {
       thief.steal();
     } else {

marker/src/main/java/Guard.java

@@ -28,11 +28,9 @@ import org.slf4j.LoggerFactory;
  * Class defining Guard.
  */
 public class Guard implements Permission {
-
   private static final Logger LOGGER = LoggerFactory.getLogger(Guard.class);
 
-  protected static void enter() {
+  protected void enter() {
-
     LOGGER.info("You can enter");
   }
 }

marker/src/main/java/Thief.java

@@ -28,14 +28,13 @@ import org.slf4j.LoggerFactory;
  * Class defining Thief.
  */
 public class Thief {
-
   private static final Logger LOGGER = LoggerFactory.getLogger(Thief.class);
 
-  protected static void steal() {
+  protected void steal() {
     LOGGER.info("Steal valuable items");
   }
 
-  protected static void doNothing() {
+  protected void doNothing() {
     LOGGER.info("Pretend nothing happened and just leave");
   }
 }

marker/src/test/java/AppTest.java

@@ -30,7 +30,6 @@ public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

marker/src/test/java/GuardTest.java

@@ -33,7 +33,7 @@ public class GuardTest {
 
   @Test
   public void testGuard() {
-    Guard guard = new Guard();
+    var guard = new Guard();
     assertThat(guard, instanceOf(Permission.class));
   }
 }

marker/src/test/java/ThiefTest.java

@@ -21,9 +21,11 @@
  * THE SOFTWARE.
  */
 
-import org.junit.jupiter.api.Test;
+import static org.hamcrest.CoreMatchers.instanceOf;
+import static org.hamcrest.CoreMatchers.not;
+import static org.hamcrest.MatcherAssert.assertThat;
 
-import static org.junit.jupiter.api.Assertions.assertFalse;
+import org.junit.jupiter.api.Test;
 
 /**
  * Thief test
@@ -31,7 +33,7 @@ import static org.junit.jupiter.api.Assertions.assertFalse;
 public class ThiefTest {
   @Test
   public void testThief() {
-    Thief thief = new Thief();
+    var thief = new Thief();
-    assertFalse(thief instanceof Permission);
+    assertThat(thief, not(instanceOf(Permission.class)));
   }
 }

master-worker-pattern/pom.xml

@@ -22,38 +22,39 @@
     THE SOFTWARE.
 
 -->
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-  <modelVersion>4.0.0</modelVersion>
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-  <parent>
+    <modelVersion>4.0.0</modelVersion>
-    <groupId>com.iluwatar</groupId>
+    <parent>
-    <artifactId>java-design-patterns</artifactId>
+        <groupId>com.iluwatar</groupId>
-    <version>1.23.0-SNAPSHOT</version>
+        <artifactId>java-design-patterns</artifactId>
-  </parent>
+        <version>1.23.0-SNAPSHOT</version>
-  <artifactId>master-worker-pattern</artifactId>
+    </parent>
-  <dependencies>
+    <artifactId>master-worker-pattern</artifactId>
-      <dependency>
+    <dependencies>
-          <groupId>org.junit.jupiter</groupId>
+        <dependency>
-          <artifactId>junit-jupiter-engine</artifactId>
+            <groupId>org.junit.jupiter</groupId>
-          <scope>test</scope>
+            <artifactId>junit-jupiter-engine</artifactId>
-      </dependency>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
-  <build>
+    <build>
-    <plugins>
+        <plugins>
-      <plugin>
+            <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
+                <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-assembly-plugin</artifactId>
+                <artifactId>maven-assembly-plugin</artifactId>
-        <executions>
+                <executions>
-          <execution>
+                    <execution>
-            <configuration>
+                        <configuration>
-              <archive>
+                            <archive>
-                <manifest>
+                                <manifest>
-                  <mainClass>com.iluwatar.masterworker.App</mainClass>
+                                    <mainClass>com.iluwatar.masterworker.App</mainClass>
-                </manifest>
+                                </manifest>
-              </archive>
+                            </archive>
-            </configuration>
+                        </configuration>
-          </execution>
+                    </execution>
-        </executions>
+                </executions>
-      </plugin>
+            </plugin>
-    </plugins>
+        </plugins>
-  </build>
+    </build>
 </project>

master-worker-pattern/src/main/java/com/iluwatar/masterworker/App.java

@@ -34,27 +34,25 @@ import org.slf4j.LoggerFactory;
 
 /**
  * <p>The <b><em>Master-Worker</em></b> pattern is used when the problem at hand can be solved by
- * dividing into
+ * dividing into multiple parts which need to go through the same computation and may need to be
- * multiple parts which need to go through the same computation and may need to be aggregated to get
+ * aggregated to get final result. Parallel processing is performed using a system consisting of a
- * final result. Parallel processing is performed using a system consisting of a master and some
+ * master and some number of workers, where a master divides the work among the workers, gets the
- * number of workers, where a master divides the work among the workers, gets the result back from
+ * result back from them and assimilates all the results to give final result. The only
- * them and assimilates all the results to give final result. The only communication is between the
+ * communication is between the master and the worker - none of the workers communicate among one
- * master and the worker - none of the workers communicate among one another and the user only
+ * another and the user only communicates with the master to get required job done.</p>
- * communicates with the master to get required job done.</p>
  * <p>In our example, we have generic abstract classes {@link MasterWorker}, {@link Master} and
- * {@link Worker} which
+ * {@link Worker} which have to be extended by the classes which will perform the specific job at
- * have to be extended by the classes which will perform the specific job at hand (in this case
+ * hand (in this case finding transpose of matrix, done by {@link ArrayTransposeMasterWorker},
- * finding transpose of matrix, done by {@link ArrayTransposeMasterWorker}, {@link
+ * {@link ArrayTransposeMaster} and {@link ArrayTransposeWorker}). The Master class divides the work
- * ArrayTransposeMaster} and {@link ArrayTransposeWorker}). The Master class divides the work into
+ * into parts to be given to the workers, collects the results from the workers and aggregates it
- * parts to be given to the workers, collects the results from the workers and aggregates it when
+ * when all workers have responded before returning the solution. The Worker class extends the
- * all workers have responded before returning the solution. The Worker class extends the Thread
+ * Thread class to enable parallel processing, and does the work once the data has been received
- * class to enable parallel processing, and does the work once the data has been received from the
+ * from the Master. The MasterWorker contains a reference to the Master class, gets the input from
- * Master. The MasterWorker contains a reference to the Master class, gets the input from the App
+ * the App and passes it on to the Master. These 3 classes define the system which computes the
- * and passes it on to the Master. These 3 classes define the system which computes the result. We
+ * result. We also have 2 abstract classes {@link Input} and {@link Result}, which contain the input
- * also have 2 abstract classes {@link Input} and {@link Result}, which contain the input data and
+ * data and result data respectively. The Input class also has an abstract method divideData which
- * result data respectively. The Input class also has an abstract method divideData which defines
+ * defines how the data is to be divided into segments. These classes are extended by {@link
- * how the data is to be divided into segments. These classes are extended by {@link ArrayInput} and
+ * ArrayInput} and {@link ArrayResult}.</p>
- * {@link ArrayResult}.</p>
  */
 
 public class App {
@@ -68,12 +66,12 @@ public class App {
    */
 
   public static void main(String[] args) {
-    ArrayTransposeMasterWorker mw = new ArrayTransposeMasterWorker();
+    var mw = new ArrayTransposeMasterWorker();
-    int rows = 10;
+    var rows = 10;
-    int columns = 20;
+    var columns = 20;
-    int[][] inputMatrix = ArrayUtilityMethods.createRandomIntMatrix(rows, columns);
+    var inputMatrix = ArrayUtilityMethods.createRandomIntMatrix(rows, columns);
-    ArrayInput input = new ArrayInput(inputMatrix);
+    var input = new ArrayInput(inputMatrix);
-    ArrayResult result = (ArrayResult) mw.getResult(input);
+    var result = (ArrayResult) mw.getResult(input);
     if (result != null) {
       ArrayUtilityMethods.printMatrix(inputMatrix);
       ArrayUtilityMethods.printMatrix(result.data);

master-worker-pattern/src/main/java/com/iluwatar/masterworker/ArrayInput.java

@@ -25,6 +25,7 @@ package com.iluwatar.masterworker;
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.List;
 
 /**
  * Class ArrayInput extends abstract class {@link Input} and contains data of type int[][].
@@ -37,12 +38,12 @@ public class ArrayInput extends Input<int[][]> {
   }
 
   static int[] makeDivisions(int[][] data, int num) {
-    int initialDivision = data.length / num; //equally dividing
+    var initialDivision = data.length / num; //equally dividing
-    int[] divisions = new int[num];
+    var divisions = new int[num];
     Arrays.fill(divisions, initialDivision);
     if (initialDivision * num != data.length) {
-      int extra = data.length - initialDivision * num;
+      var extra = data.length - initialDivision * num;
-      int l = 0;
+      var l = 0;
       //equally dividing extra among all parts
       while (extra > 0) {
         divisions[l] = divisions[l] + 1;
@@ -58,22 +59,20 @@ public class ArrayInput extends Input<int[][]> {
   }
 
   @Override
-  public ArrayList<Input> divideData(int num) {
+  public List<Input<int[][]>> divideData(int num) {
     if (this.data == null) {
       return null;
     } else {
-      int[] divisions = makeDivisions(this.data, num);
+      var divisions = makeDivisions(this.data, num);
-      ArrayList<Input> result = new ArrayList<Input>(num);
+      var result = new ArrayList<Input<int[][]>>(num);
-      int rowsDone = 0; //number of rows divided so far
+      var rowsDone = 0; //number of rows divided so far
-      for (int i = 0; i < num; i++) {
+      for (var i = 0; i < num; i++) {
-        int rows = divisions[i];
+        var rows = divisions[i];
         if (rows != 0) {
-          int[][] divided = new int[rows][this.data[0].length];
+          var divided = new int[rows][this.data[0].length];
-          for (int j = 0; j < rows; j++) {
+          System.arraycopy(this.data, rowsDone, divided, 0, rows);
-            divided[j] = this.data[rowsDone + j];
-          }
           rowsDone += rows;
-          ArrayInput dividedInput = new ArrayInput(divided);
+          var dividedInput = new ArrayInput(divided);
           result.add(dividedInput);
         } else {
           break; //rest of divisions will also be 0

master-worker-pattern/src/main/java/com/iluwatar/masterworker/ArrayUtilityMethods.java

@@ -47,8 +47,8 @@ public class ArrayUtilityMethods {
     if (a1.length != a2.length) {
       return false;
     } else {
-      boolean answer = false;
+      var answer = false;
-      for (int i = 0; i < a1.length; i++) {
+      for (var i = 0; i < a1.length; i++) {
         if (a1[i] == a2[i]) {
           answer = true;
         } else {
@@ -69,8 +69,8 @@ public class ArrayUtilityMethods {
     if (m1.length != m2.length) {
       return false;
     } else {
-      boolean answer = false;
+      var answer = false;
-      for (int i = 0; i < m1.length; i++) {
+      for (var i = 0; i < m1.length; i++) {
         if (arraysSame(m1[i], m2[i])) {
           answer = true;
         } else {
@@ -88,9 +88,9 @@ public class ArrayUtilityMethods {
    * @return it (int[][]).
    */
   public static int[][] createRandomIntMatrix(int rows, int columns) {
-    int[][] matrix = new int[rows][columns];
+    var matrix = new int[rows][columns];
-    for (int i = 0; i < rows; i++) {
+    for (var i = 0; i < rows; i++) {
-      for (int j = 0; j < columns; j++) {
+      for (var j = 0; j < columns; j++) {
         //filling cells in matrix
         matrix[i][j] = RANDOM.nextInt(10);
       }
@@ -104,9 +104,9 @@ public class ArrayUtilityMethods {
 
   public static void printMatrix(int[][] matrix) {
     //prints out int[][]
-    for (int i = 0; i < matrix.length; i++) {
+    for (var ints : matrix) {
-      for (int j = 0; j < matrix[0].length; j++) {
+      for (var j = 0; j < matrix[0].length; j++) {
-        LOGGER.info(matrix[i][j] + " ");
+        LOGGER.info(ints[j] + " ");
       }
       LOGGER.info("");
     }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/Input.java

@@ -23,7 +23,7 @@
 
 package com.iluwatar.masterworker;
 
-import java.util.ArrayList;
+import java.util.List;
 
 /**
  * The abstract Input class, having 1 public field which contains input data, and abstract method
@@ -40,5 +40,5 @@ public abstract class Input<T> {
     this.data = data;
   }
 
-  public abstract ArrayList<Input> divideData(int num);
+  public abstract List<Input<T>> divideData(int num);
 }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/system/MasterWorker.java

@@ -40,7 +40,7 @@ public abstract class MasterWorker {
 
   abstract Master setMaster(int numOfWorkers);
 
-  public Result getResult(Input input) {
+  public Result<?> getResult(Input<?> input) {
     this.master.doWork(input);
     return this.master.getFinalResult();
   }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/system/systemmaster/ArrayTransposeMaster.java

@@ -27,7 +27,8 @@ import com.iluwatar.masterworker.ArrayResult;
 import com.iluwatar.masterworker.system.systemworkers.ArrayTransposeWorker;
 import com.iluwatar.masterworker.system.systemworkers.Worker;
 import java.util.ArrayList;
-import java.util.Enumeration;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
 
 /**
  * Class ArrayTransposeMaster extends abstract class {@link Master} and contains definition of
@@ -41,35 +42,33 @@ public class ArrayTransposeMaster extends Master {
 
   @Override
   ArrayList<Worker> setWorkers(int num) {
-    ArrayList<Worker> ws = new ArrayList<Worker>(num);
+    //i+1 will be id
-    for (int i = 0; i < num; i++) {
+    return IntStream.range(0, num)
-      ws.add(new ArrayTransposeWorker(this, i + 1));
+        .mapToObj(i -> new ArrayTransposeWorker(this, i + 1))
-      //i+1 will be id
+        .collect(Collectors.toCollection(() -> new ArrayList<>(num)));
-    }
-    return ws;
   }
 
   @Override
   ArrayResult aggregateData() {
     // number of rows in final result is number of rows in any of obtained results from workers
-    int rows = ((ArrayResult) this.getAllResultData()
+    var allResultData = this.getAllResultData();
-        .get(this.getAllResultData().keys().nextElement())).data.length;
+    var rows = ((ArrayResult) allResultData.elements().nextElement()).data.length;
-    int columns =
+    var elements = allResultData.elements();
-        0; //number of columns is sum of number of columns in all results obtained from workers
+    var columns = 0; // columns = sum of number of columns in all results obtained from workers
-    for (Enumeration<Integer> e = this.getAllResultData().keys(); e.hasMoreElements(); ) {
+    while (elements.hasMoreElements()) {
-      columns += ((ArrayResult) this.getAllResultData().get(e.nextElement())).data[0].length;
+      columns += ((ArrayResult) elements.nextElement()).data[0].length;
     }
-    int[][] resultData = new int[rows][columns];
+    var resultData = new int[rows][columns];
-    int columnsDone = 0; //columns aggregated so far
+    var columnsDone = 0; //columns aggregated so far
-    for (int i = 0; i < this.getExpectedNumResults(); i++) {
+    var workers = this.getWorkers();
+    for (var i = 0; i < this.getExpectedNumResults(); i++) {
       //result obtained from ith worker
-      int[][] work =
+      var worker = workers.get(i);
-          ((ArrayResult) this.getAllResultData().get(this.getWorkers().get(i).getWorkerId())).data;
+      var workerId = worker.getWorkerId();
-      for (int m = 0; m < work.length; m++) {
+      var work = ((ArrayResult) allResultData.get(workerId)).data;
+      for (var m = 0; m < work.length; m++) {
         //m = row number, n = columns number
-        for (int n = 0; n < work[0].length; n++) {
+        System.arraycopy(work[m], 0, resultData[m], columnsDone, work[0].length);
-          resultData[m][columnsDone + n] = work[m][n];
-        }
       }
       columnsDone += work[0].length;
     }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/system/systemmaster/Master.java

@@ -26,8 +26,8 @@ package com.iluwatar.masterworker.system.systemmaster;
 import com.iluwatar.masterworker.Input;
 import com.iluwatar.masterworker.Result;
 import com.iluwatar.masterworker.system.systemworkers.Worker;
-import java.util.ArrayList;
 import java.util.Hashtable;
+import java.util.List;
 
 /**
  * The abstract Master class which contains private fields numOfWorkers (number of workers), workers
@@ -38,24 +38,24 @@ import java.util.Hashtable;
 
 public abstract class Master {
   private final int numOfWorkers;
-  private final ArrayList<Worker> workers;
+  private final List<Worker> workers;
+  private final Hashtable<Integer, Result<?>> allResultData;
   private int expectedNumResults;
-  private final Hashtable<Integer, Result> allResultData;
+  private Result<?> finalResult;
-  private Result finalResult;
 
   Master(int numOfWorkers) {
     this.numOfWorkers = numOfWorkers;
     this.workers = setWorkers(numOfWorkers);
     this.expectedNumResults = 0;
-    this.allResultData = new Hashtable<Integer, Result>(numOfWorkers);
+    this.allResultData = new Hashtable<>(numOfWorkers);
     this.finalResult = null;
   }
 
-  public Result getFinalResult() {
+  public Result<?> getFinalResult() {
     return this.finalResult;
   }
 
-  Hashtable<Integer, Result> getAllResultData() {
+  Hashtable<Integer, Result<?>> getAllResultData() {
     return this.allResultData;
   }
 
@@ -63,34 +63,41 @@ public abstract class Master {
     return this.expectedNumResults;
   }
 
-  ArrayList<Worker> getWorkers() {
+  List<Worker> getWorkers() {
     return this.workers;
   }
 
-  abstract ArrayList<Worker> setWorkers(int num);
+  abstract List<Worker> setWorkers(int num);
 
-  public void doWork(Input input) {
+  public void doWork(Input<?> input) {
     divideWork(input);
   }
 
-  private void divideWork(Input input) {
+  private void divideWork(Input<?> input) {
-    ArrayList<Input> dividedInput = input.divideData(numOfWorkers);
+    var dividedInput = input.divideData(numOfWorkers);
     if (dividedInput != null) {
       this.expectedNumResults = dividedInput.size();
-      for (int i = 0; i < this.expectedNumResults; i++) {
+      for (var i = 0; i < this.expectedNumResults; i++) {
         //ith division given to ith worker in this.workers
         this.workers.get(i).setReceivedData(this, dividedInput.get(i));
-        this.workers.get(i).run();
+        this.workers.get(i).start();
+      }
+      for (var i = 0; i < this.expectedNumResults; i++) {
+        try {
+          this.workers.get(i).join();
+        } catch (InterruptedException e) {
+          System.err.println("Error while executing thread");
+        }
       }
     }
   }
 
-  public void receiveData(Result data, Worker w) {
+  public void receiveData(Result<?> data, Worker w) {
     //check if can receive..if yes:
     collectResult(data, w.getWorkerId());
   }
 
-  private void collectResult(Result data, int workerId) {
+  private void collectResult(Result<?> data, int workerId) {
     this.allResultData.put(workerId, data);
     if (this.allResultData.size() == this.expectedNumResults) {
       //all data received
@@ -98,5 +105,5 @@ public abstract class Master {
     }
   }
 
-  abstract Result aggregateData();
+  abstract Result<?> aggregateData();
 }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/system/systemworkers/ArrayTransposeWorker.java

@@ -41,12 +41,12 @@ public class ArrayTransposeWorker extends Worker {
   @Override
   ArrayResult executeOperation() {
     //number of rows in result matrix is equal to number of columns in input matrix and vice versa
-    ArrayInput arrayInput = (ArrayInput) this.getReceivedData();
+    var arrayInput = (ArrayInput) this.getReceivedData();
-    final int rows = arrayInput.data[0].length;
+    final var rows = arrayInput.data[0].length;
-    final int cols = arrayInput.data.length;
+    final var cols = arrayInput.data.length;
-    int[][] resultData = new int[rows][cols];
+    var resultData = new int[rows][cols];
-    for (int i = 0; i < cols; i++) {
+    for (var i = 0; i < cols; i++) {
-      for (int j = 0; j < rows; j++) {
+      for (var j = 0; j < rows; j++) {
         //flipping element positions along diagonal
         resultData[j][i] = arrayInput.data[i][j];
       }

master-worker-pattern/src/main/java/com/iluwatar/masterworker/system/systemworkers/Worker.java

@@ -35,7 +35,7 @@ import com.iluwatar.masterworker.system.systemmaster.Master;
 public abstract class Worker extends Thread {
   private final Master master;
   private final int workerId;
-  private Input receivedData;
+  private Input<?> receivedData;
 
   Worker(Master master, int id) {
     this.master = master;
@@ -47,23 +47,23 @@ public abstract class Worker extends Thread {
     return this.workerId;
   }
 
-  Input getReceivedData() {
+  Input<?> getReceivedData() {
     return this.receivedData;
   }
 
-  public void setReceivedData(Master m, Input i) {
+  public void setReceivedData(Master m, Input<?> i) {
     //check if ready to receive..if yes:
     this.receivedData = i;
   }
 
-  abstract Result executeOperation();
+  abstract Result<?> executeOperation();
 
-  private void sendToMaster(Result data) {
+  private void sendToMaster(Result<?> data) {
     this.master.receiveData(data, this);
   }
 
   public void run() { //from Thread class
-    Result work = executeOperation();
+    var work = executeOperation();
     sendToMaster(work);
   }
 }

master-worker-pattern/src/test/java/com/iluwatar/masterworker/ArrayInputTest.java

@@ -23,38 +23,39 @@
 
 package com.iluwatar.masterworker;
 
-import static org.junit.jupiter.api.Assertions.*;
+import static com.iluwatar.masterworker.ArrayUtilityMethods.matricesSame;
-import java.util.ArrayList;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import java.util.Random;
 import org.junit.jupiter.api.Test;
 
 /**
-* Testing divideData method in {@link ArrayInput} class.
+ * Testing divideData method in {@link ArrayInput} class.
-*/
+ */
 
 class ArrayInputTest {
 
   @Test
   void divideDataTest() {
-    int rows = 10;
+    var rows = 10;
-    int columns = 10;
+    var columns = 10;
-    int[][] inputMatrix = new int[rows][columns];
+    var inputMatrix = new int[rows][columns];
-    Random rand = new Random();
+    var rand = new Random();
-    for (int i = 0; i < rows; i++) {
+    for (var i = 0; i < rows; i++) {
-      for (int j = 0; j < columns; j++) {
+      for (var j = 0; j < columns; j++) {
         inputMatrix[i][j] = rand.nextInt(10);
       }
     }
-    ArrayInput i = new ArrayInput(inputMatrix);
+    var i = new ArrayInput(inputMatrix);
-    ArrayList<Input> table = i.divideData(4);
+    var table = i.divideData(4);
-    int[][] division1 = new int[][] {inputMatrix[0], inputMatrix[1], inputMatrix[2]};
+    var division1 = new int[][]{inputMatrix[0], inputMatrix[1], inputMatrix[2]};
-    int[][] division2 = new int[][] {inputMatrix[3], inputMatrix[4], inputMatrix[5]};
+    var division2 = new int[][]{inputMatrix[3], inputMatrix[4], inputMatrix[5]};
-    int[][] division3 = new int[][] {inputMatrix[6], inputMatrix[7]};
+    var division3 = new int[][]{inputMatrix[6], inputMatrix[7]};
-    int[][] division4 = new int[][] {inputMatrix[8], inputMatrix[9]};
+    var division4 = new int[][]{inputMatrix[8], inputMatrix[9]};
-    assertTrue(ArrayUtilityMethods.matricesSame((int[][]) table.get(0).data, division1) 
+    assertTrue(matricesSame(table.get(0).data, division1)
-            && ArrayUtilityMethods.matricesSame((int[][]) table.get(1).data, division2)
+        && matricesSame(table.get(1).data, division2)
-            && ArrayUtilityMethods.matricesSame((int[][]) table.get(2).data, division3) 
+        && matricesSame(table.get(2).data, division3)
-            && ArrayUtilityMethods.matricesSame((int[][]) table.get(3).data, division4));
+        && matricesSame(table.get(3).data, division4));
   }
 
 }

master-worker-pattern/src/test/java/com/iluwatar/masterworker/ArrayUtilityMethodsTest.java

@@ -23,27 +23,27 @@
 
 package com.iluwatar.masterworker;
 
-import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import org.junit.jupiter.api.Test;
 
 /**
-* Testing utility methods in {@link ArrayUtilityMethods} class.
+ * Testing utility methods in {@link ArrayUtilityMethods} class.
-*/
+ */
 
 class ArrayUtilityMethodsTest {
 
   @Test
   void arraysSameTest() {
-    int[] arr1 = new int[] {1,4,2,6};
+    var arr1 = new int[]{1, 4, 2, 6};
-    int[] arr2 = new int[] {1,4,2,6};
+    var arr2 = new int[]{1, 4, 2, 6};
     assertTrue(ArrayUtilityMethods.arraysSame(arr1, arr2));
   }
 
   @Test
   void matricesSameTest() {
-    int[][] matrix1 = new int[][] {{1,4,2,6},{5,8,6,7}};
+    var matrix1 = new int[][]{{1, 4, 2, 6}, {5, 8, 6, 7}};
-    int[][] matrix2 = new int[][] {{1,4,2,6},{5,8,6,7}};
+    var matrix2 = new int[][]{{1, 4, 2, 6}, {5, 8, 6, 7}};
     assertTrue(ArrayUtilityMethods.matricesSame(matrix1, matrix2));
   }
 

master-worker-pattern/src/test/java/com/iluwatar/masterworker/system/ArrayTransposeMasterWorkerTest.java

@@ -23,25 +23,38 @@
 
 package com.iluwatar.masterworker.system;
 
-import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertTrue;
-import org.junit.jupiter.api.Test;
+
-import com.iluwatar.masterworker.ArrayUtilityMethods;
 import com.iluwatar.masterworker.ArrayInput;
 import com.iluwatar.masterworker.ArrayResult;
+import com.iluwatar.masterworker.ArrayUtilityMethods;
+import org.junit.jupiter.api.Test;
 
 /**
-* Testing getResult method in {@link ArrayTransposeMasterWorker} class.
+ * Testing getResult method in {@link ArrayTransposeMasterWorker} class.
-*/
+ */
 
 class ArrayTransposeMasterWorkerTest {
 
   @Test
   void getResultTest() {
-    ArrayTransposeMasterWorker atmw = new ArrayTransposeMasterWorker();
+    var atmw = new ArrayTransposeMasterWorker();
-    int[][] matrix = new int[][] {{1,2,3,4,5}, {1,2,3,4,5}, {1,2,3,4,5}, {1,2,3,4,5}, {1,2,3,4,5}};
+    var matrix = new int[][]{
-    int[][] matrixTranspose = new int[][] {{1,1,1,1,1}, {2,2,2,2,2}, {3,3,3,3,3}, {4,4,4,4,4}, {5,5,5,5,5}};
+        {1, 2, 3, 4, 5},
-    ArrayInput i = new ArrayInput(matrix);
+        {1, 2, 3, 4, 5},
-    ArrayResult r = (ArrayResult) atmw.getResult(i);
+        {1, 2, 3, 4, 5},
+        {1, 2, 3, 4, 5},
+        {1, 2, 3, 4, 5}
+    };
+    var matrixTranspose = new int[][]{
+        {1, 1, 1, 1, 1},
+        {2, 2, 2, 2, 2},
+        {3, 3, 3, 3, 3},
+        {4, 4, 4, 4, 4},
+        {5, 5, 5, 5, 5}
+    };
+    var i = new ArrayInput(matrix);
+    var r = (ArrayResult) atmw.getResult(i);
     assertTrue(ArrayUtilityMethods.matricesSame(r.data, matrixTranspose));
-  } 
+  }
 }

master-worker-pattern/src/test/java/com/iluwatar/masterworker/system/systemworkers/ArrayTransposeWorkerTest.java

@@ -23,29 +23,29 @@
 
 package com.iluwatar.masterworker.system.systemworkers;
 
-import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertTrue;
-import org.junit.jupiter.api.Test;
+
-import com.iluwatar.masterworker.ArrayUtilityMethods;
 import com.iluwatar.masterworker.ArrayInput;
-import com.iluwatar.masterworker.ArrayResult;
+import com.iluwatar.masterworker.ArrayUtilityMethods;
 import com.iluwatar.masterworker.system.systemmaster.ArrayTransposeMaster;
+import org.junit.jupiter.api.Test;
 
 /**
-* Testing executeOperation method in {@link ArrayTransposeWorker} class.
+ * Testing executeOperation method in {@link ArrayTransposeWorker} class.
-*/
+ */
 
 class ArrayTransposeWorkerTest {
 
   @Test
   void executeOperationTest() {
-    ArrayTransposeMaster atm = new ArrayTransposeMaster(1);
+    var atm = new ArrayTransposeMaster(1);
-    ArrayTransposeWorker atw = new ArrayTransposeWorker(atm, 1);
+    var atw = new ArrayTransposeWorker(atm, 1);
-    int[][] matrix = new int[][] {{2,4}, {3,5}};
+    var matrix = new int[][]{{2, 4}, {3, 5}};
-    int[][] matrixTranspose = new int[][] {{2,3}, {4,5}};
+    var matrixTranspose = new int[][]{{2, 3}, {4, 5}};
-    ArrayInput i = new ArrayInput(matrix);
+    var i = new ArrayInput(matrix);
     atw.setReceivedData(atm, i);
-    ArrayResult r = atw.executeOperation();
+    var r = atw.executeOperation();
     assertTrue(ArrayUtilityMethods.matricesSame(r.data, matrixTranspose));
   }
-  
+
 }

mediator/src/main/java/com/iluwatar/mediator/Action.java

@@ -27,7 +27,6 @@ package com.iluwatar.mediator;
  * Action enumeration.
  */
 public enum Action {
-
   HUNT("hunted a rabbit", "arrives for dinner"),
   TALE("tells a tale", "comes to listen"),
   GOLD("found gold", "takes his share of the gold"),

mediator/src/main/java/com/iluwatar/mediator/App.java

@@ -55,10 +55,10 @@ public class App {
 
     // create party and members
     Party party = new PartyImpl();
-    Hobbit hobbit = new Hobbit();
+    var hobbit = new Hobbit();
-    Wizard wizard = new Wizard();
+    var wizard = new Wizard();
-    Rogue rogue = new Rogue();
+    var rogue = new Rogue();
-    Hunter hunter = new Hunter();
+    var hunter = new Hunter();
 
     // add party members
     party.addMember(hobbit);

mediator/src/main/java/com/iluwatar/mediator/PartyImpl.java

@@ -39,7 +39,7 @@ public class PartyImpl implements Party {
 
   @Override
   public void act(PartyMember actor, Action action) {
-    for (PartyMember member : members) {
+    for (var member : members) {
       if (!member.equals(actor)) {
         member.partyAction(action);
       }

mediator/src/test/java/com/iluwatar/mediator/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.mediator;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

mediator/src/test/java/com/iluwatar/mediator/PartyImplTest.java

@@ -43,10 +43,10 @@ public class PartyImplTest {
    */
   @Test
   public void testPartyAction() {
-    final PartyMember partyMember1 = mock(PartyMember.class);
+    final var partyMember1 = mock(PartyMember.class);
-    final PartyMember partyMember2 = mock(PartyMember.class);
+    final var partyMember2 = mock(PartyMember.class);
 
-    final PartyImpl party = new PartyImpl();
+    final var party = new PartyImpl();
     party.addMember(partyMember1);
     party.addMember(partyMember2);
 
@@ -58,7 +58,6 @@ public class PartyImplTest {
     verify(partyMember2).partyAction(Action.GOLD);
 
     verifyNoMoreInteractions(partyMember1, partyMember2);
-
   }
 
 }

mediator/src/test/java/com/iluwatar/mediator/PartyMemberTest.java

@@ -23,24 +23,24 @@
 
 package com.iluwatar.mediator;
 
-import ch.qos.logback.classic.Logger;
-import ch.qos.logback.classic.spi.ILoggingEvent;
-import ch.qos.logback.core.AppenderBase;
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.params.ParameterizedTest;
-import org.junit.jupiter.params.provider.MethodSource;
-import org.slf4j.LoggerFactory;
-
-import java.util.Collection;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.function.Supplier;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.AppenderBase;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.slf4j.LoggerFactory;
+
 /**
  * Date: 12/19/15 - 10:13 PM
  *
@@ -48,12 +48,12 @@ import static org.mockito.Mockito.verify;
  */
 public class PartyMemberTest {
 
-  static Collection<Supplier<PartyMember>[]> dataProvider() {
+  static Stream<Arguments> dataProvider() {
-    return List.of(
+    return Stream.of(
-            new Supplier[]{Hobbit::new},
+        Arguments.of((Supplier<PartyMember>) Hobbit::new),
-            new Supplier[]{Hunter::new},
+        Arguments.of((Supplier<PartyMember>) Hunter::new),
-            new Supplier[]{Rogue::new},
+        Arguments.of((Supplier<PartyMember>) Rogue::new),
-            new Supplier[]{Wizard::new}
+        Arguments.of((Supplier<PartyMember>) Wizard::new)
     );
   }
 
@@ -75,9 +75,9 @@ public class PartyMemberTest {
   @ParameterizedTest
   @MethodSource("dataProvider")
   public void testPartyAction(Supplier<PartyMember> memberSupplier) {
-    final PartyMember member = memberSupplier.get();
+    final var member = memberSupplier.get();
 
-    for (final Action action : Action.values()) {
+    for (final var action : Action.values()) {
       member.partyAction(action);
       assertEquals(member.toString() + " " + action.getDescription(), appender.getLastMessage());
     }
@@ -91,16 +91,16 @@ public class PartyMemberTest {
   @ParameterizedTest
   @MethodSource("dataProvider")
   public void testAct(Supplier<PartyMember> memberSupplier) {
-    final PartyMember member = memberSupplier.get();
+    final var member = memberSupplier.get();
 
     member.act(Action.GOLD);
     assertEquals(0, appender.getLogSize());
 
-    final Party party = mock(Party.class);
+    final var party = mock(Party.class);
     member.joinedParty(party);
     assertEquals(member.toString() + " joins the party", appender.getLastMessage());
 
-    for (final Action action : Action.values()) {
+    for (final var action : Action.values()) {
       member.act(action);
       assertEquals(member.toString() + " " + action.toString(), appender.getLastMessage());
       verify(party).act(member, action);
@@ -114,16 +114,16 @@ public class PartyMemberTest {
    */
   @ParameterizedTest
   @MethodSource("dataProvider")
-  public void testToString(Supplier<PartyMember> memberSupplier) throws Exception {
+  public void testToString(Supplier<PartyMember> memberSupplier) {
-    final PartyMember member = memberSupplier.get();
+    final var member = memberSupplier.get();
-    final Class<? extends PartyMember> memberClass = member.getClass();
+    final var memberClass = member.getClass();
     assertEquals(memberClass.getSimpleName(), member.toString());
   }
 
-  private class InMemoryAppender extends AppenderBase<ILoggingEvent> {
+  private static class InMemoryAppender extends AppenderBase<ILoggingEvent> {
     private final List<ILoggingEvent> log = new LinkedList<>();
 
-    public InMemoryAppender(Class clazz) {
+    public InMemoryAppender(Class<?> clazz) {
       ((Logger) LoggerFactory.getLogger(clazz)).addAppender(this);
       start();
     }

memento/README.md

@@ -34,9 +34,12 @@ Let's first define the types of stars we are capable to handle.
 
 ```java
 public enum StarType {
-
+  SUN("sun"),
-  SUN("sun"), RED_GIANT("red giant"), WHITE_DWARF("white dwarf"), SUPERNOVA("supernova"), DEAD(
+  RED_GIANT("red giant"),
-      "dead star"), UNDEFINED("");
+  WHITE_DWARF("white dwarf"),
+  SUPERNOVA("supernova"),
+  DEAD("dead star"),
+  UNDEFINED("");
 
   private final String title;
 
@@ -95,8 +98,7 @@ public class Star {
   }
 
   StarMemento getMemento() {
-
+    var state = new StarMementoInternal();
-    StarMementoInternal state = new StarMementoInternal();
     state.setAgeYears(ageYears);
     state.setMassTons(massTons);
     state.setType(type);
@@ -104,8 +106,7 @@ public class Star {
   }
 
   void setMemento(StarMemento memento) {
-
+    var state = (StarMementoInternal) memento;
-    StarMementoInternal state = (StarMementoInternal) memento;
     this.type = state.getType();
     this.ageYears = state.getAgeYears();
     this.massTons = state.getMassTons();
@@ -152,8 +153,8 @@ public class Star {
 And finally here's how we use the mementos to store and restore star states.
 
 ```java
-    Stack<StarMemento> states = new Stack<>();
+    var states = new Stack<>();
-    Star star = new Star(StarType.SUN, 10000000, 500000);
+    var star = new Star(StarType.SUN, 10000000, 500000);
     LOGGER.info(star.toString());
     states.add(star.getMemento());
     star.timePasses();

memento/src/main/java/com/iluwatar/memento/App.java

@@ -52,9 +52,9 @@ public class App {
    * Program entry point.
    */
   public static void main(String[] args) {
-    Stack<StarMemento> states = new Stack<>();
+    var states = new Stack<StarMemento>();
 
-    Star star = new Star(StarType.SUN, 10000000, 500000);
+    var star = new Star(StarType.SUN, 10000000, 500000);
     LOGGER.info(star.toString());
     states.add(star.getMemento());
     star.timePasses();

memento/src/main/java/com/iluwatar/memento/Star.java

@@ -70,22 +70,18 @@ public class Star {
   }
 
   StarMemento getMemento() {
-
+    var state = new StarMementoInternal();
-    StarMementoInternal state = new StarMementoInternal();
     state.setAgeYears(ageYears);
     state.setMassTons(massTons);
     state.setType(type);
     return state;
-
   }
 
   void setMemento(StarMemento memento) {
-
+    var state = (StarMementoInternal) memento;
-    StarMementoInternal state = (StarMementoInternal) memento;
     this.type = state.getType();
     this.ageYears = state.getAgeYears();
     this.massTons = state.getMassTons();
-
   }
 
   @Override

memento/src/main/java/com/iluwatar/memento/StarType.java

@@ -27,9 +27,12 @@ package com.iluwatar.memento;
  * StarType enumeration.
  */
 public enum StarType {
-
+  SUN("sun"),
-  SUN("sun"), RED_GIANT("red giant"), WHITE_DWARF("white dwarf"), SUPERNOVA("supernova"), DEAD(
+  RED_GIANT("red giant"),
-      "dead star"), UNDEFINED("");
+  WHITE_DWARF("white dwarf"),
+  SUPERNOVA("supernova"),
+  DEAD("dead star"),
+  UNDEFINED("");
 
   private final String title;
 

memento/src/test/java/com/iluwatar/memento/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.memento;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

memento/src/test/java/com/iluwatar/memento/StarTest.java

@@ -23,10 +23,10 @@
 
 package com.iluwatar.memento;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/20/15 - 10:08 AM
  *
@@ -39,7 +39,7 @@ public class StarTest {
    */
   @Test
   public void testTimePasses() {
-    final Star star = new Star(StarType.SUN, 1, 2);
+    final var star = new Star(StarType.SUN, 1, 2);
     assertEquals("sun age: 1 years mass: 2 tons", star.toString());
 
     star.timePasses();
@@ -66,16 +66,16 @@ public class StarTest {
    */
   @Test
   public void testSetMemento() {
-    final Star star = new Star(StarType.SUN, 1, 2);
+    final var star = new Star(StarType.SUN, 1, 2);
-    final StarMemento firstMemento = star.getMemento();
+    final var firstMemento = star.getMemento();
     assertEquals("sun age: 1 years mass: 2 tons", star.toString());
 
     star.timePasses();
-    final StarMemento secondMemento = star.getMemento();
+    final var secondMemento = star.getMemento();
     assertEquals("red giant age: 2 years mass: 16 tons", star.toString());
 
     star.timePasses();
-    final StarMemento thirdMemento = star.getMemento();
+    final var thirdMemento = star.getMemento();
     assertEquals("white dwarf age: 4 years mass: 128 tons", star.toString());
 
     star.timePasses();

model-view-controller/src/main/java/com/iluwatar/model/view/controller/App.java

@@ -47,9 +47,9 @@ public class App {
    */
   public static void main(String[] args) {
     // create model, view and controller
-    GiantModel giant = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
+    var giant = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
-    GiantView view = new GiantView();
+    var view = new GiantView();
-    GiantController controller = new GiantController(giant, view);
+    var controller = new GiantController(giant, view);
     // initial display
     controller.updateView();
     // controller receives some interactions that affect the giant

model-view-controller/src/main/java/com/iluwatar/model/view/controller/Fatigue.java

@@ -27,8 +27,9 @@ package com.iluwatar.model.view.controller;
  * Fatigue enumeration.
  */
 public enum Fatigue {
-
+  ALERT("alert"),
-  ALERT("alert"), TIRED("tired"), SLEEPING("sleeping");
+  TIRED("tired"),
+  SLEEPING("sleeping");
 
   private final String title;
 

model-view-controller/src/main/java/com/iluwatar/model/view/controller/GiantController.java

@@ -36,6 +36,7 @@ public class GiantController {
     this.view = view;
   }
 
+  @SuppressWarnings("UnusedReturnValue")
   public Health getHealth() {
     return giant.getHealth();
   }
@@ -44,6 +45,7 @@ public class GiantController {
     this.giant.setHealth(health);
   }
 
+  @SuppressWarnings("UnusedReturnValue")
   public Fatigue getFatigue() {
     return giant.getFatigue();
   }
@@ -52,6 +54,7 @@ public class GiantController {
     this.giant.setFatigue(fatigue);
   }
 
+  @SuppressWarnings("UnusedReturnValue")
   public Nourishment getNourishment() {
     return giant.getNourishment();
   }

model-view-controller/src/main/java/com/iluwatar/model/view/controller/Health.java

@@ -27,8 +27,9 @@ package com.iluwatar.model.view.controller;
  * Health enumeration.
  */
 public enum Health {
-
+  HEALTHY("healthy"),
-  HEALTHY("healthy"), WOUNDED("wounded"), DEAD("dead");
+  WOUNDED("wounded"),
+  DEAD("dead");
 
   private final String title;
 

model-view-controller/src/main/java/com/iluwatar/model/view/controller/Nourishment.java

@@ -27,8 +27,9 @@ package com.iluwatar.model.view.controller;
  * Nourishment enumeration.
  */
 public enum Nourishment {
-
+  SATURATED("saturated"),
-  SATURATED("saturated"), HUNGRY("hungry"), STARVING("starving");
+  HUNGRY("hungry"),
+  STARVING("starving");
 
   private final String title;
 

model-view-controller/src/test/java/com/iluwatar/model/view/controller/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.model.view.controller;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

model-view-controller/src/test/java/com/iluwatar/model/view/controller/GiantControllerTest.java

@@ -23,13 +23,13 @@
 
 package com.iluwatar.model.view.controller;
 
-import org.junit.jupiter.api.Test;
-
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.mockito.Mockito.verifyZeroInteractions;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/20/15 - 2:19 PM
  *
@@ -42,19 +42,20 @@ public class GiantControllerTest {
    */
   @Test
   public void testSetHealth() {
-    final GiantModel model = mock(GiantModel.class);
+    final var model = mock(GiantModel.class);
-    final GiantView view = mock(GiantView.class);
+    final var view = mock(GiantView.class);
-    final GiantController controller = new GiantController(model, view);
+    final var controller = new GiantController(model, view);
 
     verifyZeroInteractions(model, view);
 
-    for (final Health health : Health.values()) {
+    for (final var health : Health.values()) {
       controller.setHealth(health);
       verify(model).setHealth(health);
       verifyZeroInteractions(view);
     }
 
     controller.getHealth();
+    //noinspection ResultOfMethodCallIgnored
     verify(model).getHealth();
 
     verifyNoMoreInteractions(model, view);
@@ -65,19 +66,20 @@ public class GiantControllerTest {
    */
   @Test
   public void testSetFatigue() {
-    final GiantModel model = mock(GiantModel.class);
+    final var model = mock(GiantModel.class);
-    final GiantView view = mock(GiantView.class);
+    final var view = mock(GiantView.class);
-    final GiantController controller = new GiantController(model, view);
+    final var controller = new GiantController(model, view);
 
     verifyZeroInteractions(model, view);
 
-    for (final Fatigue fatigue : Fatigue.values()) {
+    for (final var fatigue : Fatigue.values()) {
       controller.setFatigue(fatigue);
       verify(model).setFatigue(fatigue);
       verifyZeroInteractions(view);
     }
 
     controller.getFatigue();
+    //noinspection ResultOfMethodCallIgnored
     verify(model).getFatigue();
 
     verifyNoMoreInteractions(model, view);
@@ -88,19 +90,20 @@ public class GiantControllerTest {
    */
   @Test
   public void testSetNourishment() {
-    final GiantModel model = mock(GiantModel.class);
+    final var model = mock(GiantModel.class);
-    final GiantView view = mock(GiantView.class);
+    final var view = mock(GiantView.class);
-    final GiantController controller = new GiantController(model, view);
+    final var controller = new GiantController(model, view);
 
     verifyZeroInteractions(model, view);
 
-    for (final Nourishment nourishment : Nourishment.values()) {
+    for (final var nourishment : Nourishment.values()) {
       controller.setNourishment(nourishment);
       verify(model).setNourishment(nourishment);
       verifyZeroInteractions(view);
     }
 
     controller.getNourishment();
+    //noinspection ResultOfMethodCallIgnored
     verify(model).getNourishment();
 
     verifyNoMoreInteractions(model, view);
@@ -108,9 +111,9 @@ public class GiantControllerTest {
 
   @Test
   public void testUpdateView() {
-    final GiantModel model = mock(GiantModel.class);
+    final var model = mock(GiantModel.class);
-    final GiantView view = mock(GiantView.class);
+    final var view = mock(GiantView.class);
-    final GiantController controller = new GiantController(model, view);
+    final var controller = new GiantController(model, view);
 
     verifyZeroInteractions(model, view);
 

model-view-controller/src/test/java/com/iluwatar/model/view/controller/GiantModelTest.java

@@ -23,10 +23,10 @@
 
 package com.iluwatar.model.view.controller;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/20/15 - 2:10 PM
  *
@@ -39,12 +39,13 @@ public class GiantModelTest {
    */
   @Test
   public void testSetHealth() {
-    final GiantModel model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
+    final var model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
     assertEquals(Health.HEALTHY, model.getHealth());
-    for (final Health health : Health.values()) {
+    var messageFormat = "The giant looks %s, alert and saturated.";
+    for (final var health : Health.values()) {
       model.setHealth(health);
       assertEquals(health, model.getHealth());
-      assertEquals("The giant looks " + health.toString() + ", alert and saturated.", model.toString());
+      assertEquals(String.format(messageFormat, health), model.toString());
     }
   }
 
@@ -53,12 +54,13 @@ public class GiantModelTest {
    */
   @Test
   public void testSetFatigue() {
-    final GiantModel model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
+    final var model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
     assertEquals(Fatigue.ALERT, model.getFatigue());
-    for (final Fatigue fatigue : Fatigue.values()) {
+    var messageFormat = "The giant looks healthy, %s and saturated.";
+    for (final var fatigue : Fatigue.values()) {
       model.setFatigue(fatigue);
       assertEquals(fatigue, model.getFatigue());
-      assertEquals("The giant looks healthy, " + fatigue.toString() + " and saturated.", model.toString());
+      assertEquals(String.format(messageFormat, fatigue), model.toString());
     }
   }
 
@@ -67,12 +69,13 @@ public class GiantModelTest {
    */
   @Test
   public void testSetNourishment() {
-    final GiantModel model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
+    final var model = new GiantModel(Health.HEALTHY, Fatigue.ALERT, Nourishment.SATURATED);
     assertEquals(Nourishment.SATURATED, model.getNourishment());
-    for (final Nourishment nourishment : Nourishment.values()) {
+    var messageFormat = "The giant looks healthy, alert and %s.";
+    for (final var nourishment : Nourishment.values()) {
       model.setNourishment(nourishment);
       assertEquals(nourishment, model.getNourishment());
-      assertEquals("The giant looks healthy, alert and " + nourishment.toString() + ".", model.toString());
+      assertEquals(String.format(messageFormat, nourishment), model.toString());
     }
   }
 

model-view-controller/src/test/java/com/iluwatar/model/view/controller/GiantViewTest.java

@@ -31,7 +31,6 @@ import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.core.AppenderBase;
 import java.util.LinkedList;
 import java.util.List;
-
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -62,9 +61,9 @@ public class GiantViewTest {
    */
   @Test
   public void testDisplayGiant() {
-    final GiantView view = new GiantView();
+    final var view = new GiantView();
 
-    final GiantModel model = mock(GiantModel.class);
+    final var model = mock(GiantModel.class);
     view.displayGiant(model);
 
     assertEquals(model.toString(), appender.getLastMessage());
@@ -74,10 +73,10 @@ public class GiantViewTest {
   /**
    * Logging Appender Implementation
    */
-  public class InMemoryAppender extends AppenderBase<ILoggingEvent> {
+  public static class InMemoryAppender extends AppenderBase<ILoggingEvent> {
     private final List<ILoggingEvent> log = new LinkedList<>();
 
-    public InMemoryAppender(Class clazz) {
+    public InMemoryAppender(Class<?> clazz) {
       ((Logger) LoggerFactory.getLogger(clazz)).addAppender(this);
       start();
     }

model-view-presenter/src/main/java/com/iluwatar/model/view/presenter/App.java

@@ -44,9 +44,9 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    FileLoader loader = new FileLoader();
+    var loader = new FileLoader();
-    FileSelectorJFrame frame = new FileSelectorJFrame();
+    var frame = new FileSelectorJFrame();
-    FileSelectorPresenter presenter = new FileSelectorPresenter(frame);
+    var presenter = new FileSelectorPresenter(frame);
     presenter.setLoader(loader);
     presenter.start();
   }

model-view-presenter/src/main/java/com/iluwatar/model/view/presenter/FileLoader.java

@@ -27,6 +27,7 @@ import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileReader;
 import java.io.Serializable;
+import java.util.stream.Collectors;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -59,18 +60,11 @@ public class FileLoader implements Serializable {
    * Loads the data of the file specified.
    */
   public String loadData() {
-    String dataFileName = this.fileName;
+    var dataFileName = this.fileName;
-    try (BufferedReader br = new BufferedReader(new FileReader(new File(dataFileName)))) {
+    try (var br = new BufferedReader(new FileReader(new File(dataFileName)))) {
-      StringBuilder sb = new StringBuilder();
+      var result = br.lines().collect(Collectors.joining("\n"));
-      String line;
-
-      while ((line = br.readLine()) != null) {
-        sb.append(line).append('\n');
-      }
-
       this.loaded = true;
-
+      return result;
-      return sb.toString();
     } catch (Exception e) {
       LOGGER.error("File {} does not exist", dataFileName);
     }

model-view-presenter/src/main/java/com/iluwatar/model/view/presenter/FileSelectorJFrame.java

@@ -55,16 +55,6 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
    */
   private final JButton cancel;
 
-  /**
-   * The information label.
-   */
-  private final JLabel info;
-
-  /**
-   * The contents label.
-   */
-  private final JLabel contents;
-
   /**
    * The text field for giving the name of the file that we want to open.
    */
@@ -75,11 +65,6 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
    */
   private final JTextArea area;
 
-  /**
-   * The panel that will hold our widgets.
-   */
-  private final JPanel panel;
-
   /**
    * The Presenter component that the frame will interact with.
    */
@@ -102,7 +87,7 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
     /*
      * Add the panel.
      */
-    this.panel = new JPanel();
+    var panel = new JPanel();
     panel.setLayout(null);
     this.add(panel);
     panel.setBounds(0, 0, 500, 200);
@@ -111,32 +96,32 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
     /*
      * Add the info label.
      */
-    this.info = new JLabel("File Name :");
+    var info = new JLabel("File Name :");
-    this.panel.add(info);
+    panel.add(info);
     info.setBounds(30, 10, 100, 30);
 
     /*
      * Add the contents label.
      */
-    this.contents = new JLabel("File contents :");
+    var contents = new JLabel("File contents :");
-    this.panel.add(contents);
+    panel.add(contents);
-    this.contents.setBounds(30, 100, 120, 30);
+    contents.setBounds(30, 100, 120, 30);
 
     /*
      * Add the text field.
      */
     this.input = new JTextField(100);
-    this.panel.add(input);
+    panel.add(input);
     this.input.setBounds(150, 15, 200, 20);
 
     /*
      * Add the text area.
      */
     this.area = new JTextArea(100, 100);
-    JScrollPane pane = new JScrollPane(area);
+    var pane = new JScrollPane(area);
     pane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
     pane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
-    this.panel.add(pane);
+    panel.add(pane);
     this.area.setEditable(false);
     pane.setBounds(150, 100, 250, 80);
 
@@ -144,7 +129,7 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
      * Add the OK button.
      */
     this.ok = new JButton("OK");
-    this.panel.add(ok);
+    panel.add(ok);
     this.ok.setBounds(250, 50, 100, 25);
     this.ok.addActionListener(this);
 
@@ -152,7 +137,7 @@ public class FileSelectorJFrame extends JFrame implements FileSelectorView, Acti
      * Add the cancel button.
      */
     this.cancel = new JButton("Cancel");
-    this.panel.add(this.cancel);
+    panel.add(this.cancel);
     this.cancel.setBounds(380, 50, 100, 25);
     this.cancel.addActionListener(this);
 

model-view-presenter/src/main/java/com/iluwatar/model/view/presenter/FileSelectorPresenter.java

@@ -91,7 +91,7 @@ public class FileSelectorPresenter implements Serializable {
     }
 
     if (loader.fileExists()) {
-      String data = loader.loadData();
+      var data = loader.loadData();
       view.displayData(data);
     } else {
       view.showMessage("The file specified does not exist.");

model-view-presenter/src/test/java/com/iluwatar/model/view/presenter/AppTest.java

@@ -26,16 +26,13 @@ package com.iluwatar.model.view.presenter;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 
 }

model-view-presenter/src/test/java/com/iluwatar/model/view/presenter/FileLoaderTest.java

@@ -23,10 +23,10 @@
 
 package com.iluwatar.model.view.presenter;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertNull;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Date: 12/21/15 - 12:12 PM
  *
@@ -35,8 +35,8 @@ import static org.junit.jupiter.api.Assertions.assertNull;
 public class FileLoaderTest {
 
   @Test
-  public void testLoadData() throws Exception {
+  public void testLoadData() {
-    final FileLoader fileLoader = new FileLoader();
+    final var fileLoader = new FileLoader();
     fileLoader.setFileName("non-existing-file");
     assertNull(fileLoader.loadData());
   }

model-view-presenter/src/test/java/com/iluwatar/model/view/presenter/FileSelectorPresenterTest.java

@@ -23,14 +23,14 @@
 
 package com.iluwatar.model.view.presenter;
 
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
 /**
  * This test case is responsible for testing our application by taking advantage of the
  * Model-View-Controller architectural pattern.
@@ -79,7 +79,7 @@ public class FileSelectorPresenterTest {
    */
   @Test
   public void updateFileNameToLoader() {
-    String expectedFile = "Stamatis";
+    var expectedFile = "Stamatis";
     stub.setFileName(expectedFile);
 
     presenter.start();

module/pom.xml

@@ -23,38 +23,39 @@
     THE SOFTWARE.
 
 -->
-<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
-	<modelVersion>4.0.0</modelVersion>
+         xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
-	<parent>
+    <modelVersion>4.0.0</modelVersion>
-		<groupId>com.iluwatar</groupId>
+    <parent>
-		<artifactId>java-design-patterns</artifactId>
+        <groupId>com.iluwatar</groupId>
-		<version>1.23.0-SNAPSHOT</version>
+        <artifactId>java-design-patterns</artifactId>
-	</parent>
+        <version>1.23.0-SNAPSHOT</version>
-	<artifactId>module</artifactId>
+    </parent>
-	<dependencies>
+    <artifactId>module</artifactId>
-		<dependency>
+    <dependencies>
-			<groupId>org.junit.jupiter</groupId>
+        <dependency>
-			<artifactId>junit-jupiter-engine</artifactId>
+            <groupId>org.junit.jupiter</groupId>
-			<scope>test</scope>
+            <artifactId>junit-jupiter-engine</artifactId>
-		</dependency>
+            <scope>test</scope>
-	</dependencies>
+        </dependency>
-	<build>
+    </dependencies>
-		<plugins>
+    <build>
-			<plugin>
+        <plugins>
-				<groupId>org.apache.maven.plugins</groupId>
+            <plugin>
-				<artifactId>maven-assembly-plugin</artifactId>
+                <groupId>org.apache.maven.plugins</groupId>
-				<executions>
+                <artifactId>maven-assembly-plugin</artifactId>
-					<execution>
+                <executions>
-						<configuration>
+                    <execution>
-							<archive>
+                        <configuration>
-								<manifest>
+                            <archive>
-									<mainClass>com.iluwatar.module.App</mainClass>
+                                <manifest>
-								</manifest>
+                                    <mainClass>com.iluwatar.module.App</mainClass>
-							</archive>
+                                </manifest>
-						</configuration>
+                            </archive>
-					</execution>
+                        </configuration>
-				</executions>
+                    </execution>
-			</plugin>
+                </executions>
-		</plugins>
+            </plugin>
-	</build>
+        </plugins>
+    </build>
 </project>

module/src/main/java/com/iluwatar/module/App.java

@@ -67,10 +67,8 @@ public class App {
 
   /**
    * Following method is main executor.
-   *
-   * @param args for providing default program arguments
    */
-  public static void execute(final String... args) {
+  public static void execute() {
 
     /* Send logs on file system */
     fileLoggerModule.printString(MESSAGE);
@@ -90,7 +88,7 @@ public class App {
    */
   public static void main(final String... args) throws FileNotFoundException {
     prepare();
-    execute(args);
+    execute();
     unprepare();
   }
 }

module/src/test/java/com/iluwatar/module/AppTest.java

@@ -23,9 +23,8 @@
 
 package com.iluwatar.module;
 
-import org.junit.jupiter.api.Test;
-
 import java.io.FileNotFoundException;
+import org.junit.jupiter.api.Test;
 
 /**
  * Tests that Module example runs without errors.
@@ -34,7 +33,6 @@ public final class AppTest {
 
   @Test
   public void test() throws FileNotFoundException {
-    final String[] args = {};
+    App.main();
-    App.main(args);
   }
 }

module/src/test/java/com/iluwatar/module/FileLoggerModuleTest.java

@@ -23,17 +23,16 @@
 
 package com.iluwatar.module;
 
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
-import org.slf4j.Logger;
+import static org.junit.jupiter.api.Assertions.assertNull;
-import org.slf4j.LoggerFactory;
 
 import java.io.BufferedReader;
 import java.io.FileNotFoundException;
 import java.io.FileReader;
 import java.io.IOException;
-
+import org.junit.jupiter.api.Test;
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.slf4j.Logger;
-import static org.junit.jupiter.api.Assertions.assertNull;
+import org.slf4j.LoggerFactory;
 
 /**
  * The Module pattern can be considered a Creational pattern and a Structural pattern. It manages
@@ -58,7 +57,7 @@ public final class FileLoggerModuleTest {
 
   /**
    * This test verify that 'MESSAGE' is perfectly printed in output file
-   * 
+   *
    * @throws IOException if program is not able to find log files (output.txt and error.txt)
    */
   @Test
@@ -82,13 +81,13 @@ public final class FileLoggerModuleTest {
 
   /**
    * This test verify that nothing is printed in output file
-   * 
+   *
    * @throws IOException if program is not able to find log files (output.txt and error.txt)
    */
   @Test
   public void testNoFileMessage() throws IOException {
 
-    /* Get singletong instance of File Logger Module */
+    /* Get singleton instance of File Logger Module */
     final var fileLoggerModule = FileLoggerModule.getSingleton();
 
     /* Prepare the essential sub modules, to perform the sequence of jobs */
@@ -103,9 +102,9 @@ public final class FileLoggerModuleTest {
 
   /**
    * This test verify that 'ERROR' is perfectly printed in error file
-   * 
+   *
    * @throws FileNotFoundException if program is not able to find log files (output.txt and
-   *         error.txt)
+   *                               error.txt)
    */
   @Test
   public void testFileErrorMessage() throws FileNotFoundException {
@@ -122,15 +121,15 @@ public final class FileLoggerModuleTest {
     /* Test if 'Message' is printed in file */
     assertEquals(ERROR, readFirstLine(ERROR_FILE));
 
-    /* Unprepare to cleanup the modules */
+    /* Un-prepare to cleanup the modules */
     fileLoggerModule.unprepare();
   }
 
   /**
    * This test verify that nothing is printed in error file
-   * 
+   *
    * @throws FileNotFoundException if program is not able to find log files (output.txt and
-   *         error.txt)
+   *                               error.txt)
    */
   @Test
   public void testNoFileErrorMessage() throws FileNotFoundException {
@@ -150,11 +149,11 @@ public final class FileLoggerModuleTest {
 
   /**
    * Utility method to read first line of a file
-   * 
+   *
    * @param file as file name to be read
    * @return a string value as first line in file
    */
-  private static final String readFirstLine(final String file) {
+  private static String readFirstLine(final String file) {
 
     String firstLine = null;
     try (var bufferedReader = new BufferedReader(new FileReader(file))) {

monad/src/main/java/com/iluwatar/monad/App.java

@@ -41,9 +41,8 @@ import org.slf4j.LoggerFactory;
  * instance of a plain object with {@link Validator#of(Object)} and validates it {@link
  * Validator#validate(Function, Predicate, String)} against given predicates.
  *
- * <p>As a validation result {@link Validator#get()} it either returns valid object {@link
+ * <p>As a validation result {@link Validator#get()} either returns valid object
- * Validator#t} or throws a list of exceptions {@link Validator#exceptions} collected during
+ * or throws {@link IllegalStateException} with list of exceptions collected during validation.
- * validation.
  */
 public class App {
 
@@ -55,10 +54,10 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    User user = new User("user", 24, Sex.FEMALE, "foobar.com");
+    var user = new User("user", 24, Sex.FEMALE, "foobar.com");
     LOGGER.info(Validator.of(user).validate(User::getName, Objects::nonNull, "name is null")
         .validate(User::getName, name -> !name.isEmpty(), "name is empty")
-        .validate(User::getEmail, email -> !email.contains("@"), "email doesn't containt '@'")
+        .validate(User::getEmail, email -> !email.contains("@"), "email doesn't contains '@'")
         .validate(User::getAge, age -> age > 20 && age < 30, "age isn't between...").get()
         .toString());
   }

monad/src/main/java/com/iluwatar/monad/Validator.java

@@ -85,18 +85,21 @@ public class Validator<T> {
   }
 
   /**
-   * Extension for the {@link Validator#validate(Function, Predicate, String)} method, dedicated for
+   * Extension for the {@link Validator#validate(Predicate, String)} method, dedicated for objects,
-   * objects, that need to be projected before requested validation.
+   * that need to be projected before requested validation.
    *
    * @param projection function that gets an objects, and returns projection representing element to
    *                   be validated.
-   * @param validation see {@link Validator#validate(Function, Predicate, String)}
+   * @param validation see {@link Validator#validate(Predicate, String)}
-   * @param message    see {@link Validator#validate(Function, Predicate, String)}
+   * @param message    see {@link Validator#validate(Predicate, String)}
-   * @param <U>        see {@link Validator#validate(Function, Predicate, String)}
+   * @param <U>        see {@link Validator#validate(Predicate, String)}
    * @return this
    */
-  public <U> Validator<T> validate(Function<T, U> projection, Predicate<U> validation,
+  public <U> Validator<T> validate(
-                                   String message) {
+      Function<T, U> projection,
+      Predicate<U> validation,
+      String message
+  ) {
     return validate(projection.andThen(validation::test)::apply, message);
   }
 
@@ -110,7 +113,7 @@ public class Validator<T> {
     if (exceptions.isEmpty()) {
       return obj;
     }
-    IllegalStateException e = new IllegalStateException();
+    var e = new IllegalStateException();
     exceptions.forEach(e::addSuppressed);
     throw e;
   }

monad/src/test/java/com/iluwatar/monad/AppTest.java

@@ -32,8 +32,7 @@ public class AppTest {
 
   @Test
   public void testMain() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 
 }

monad/src/test/java/com/iluwatar/monad/MonadTest.java

@@ -23,13 +23,12 @@
 
 package com.iluwatar.monad;
 
-import org.junit.jupiter.api.Test;
-
-import java.util.Objects;
-
 import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
+import java.util.Objects;
+import org.junit.jupiter.api.Test;
+
 /**
  * Test for Monad Pattern
  */
@@ -37,27 +36,33 @@ public class MonadTest {
 
   @Test
   public void testForInvalidName() {
-    User tom = new User(null, 21, Sex.MALE, "tom@foo.bar");
+    var tom = new User(null, 21, Sex.MALE, "tom@foo.bar");
-    assertThrows(IllegalStateException.class, () -> {
+    assertThrows(
-      Validator.of(tom).validate(User::getName, Objects::nonNull, "name cannot be null").get();
+        IllegalStateException.class,
-    });
+        () -> Validator.of(tom)
+            .validate(User::getName, Objects::nonNull, "name cannot be null")
+            .get()
+    );
   }
 
   @Test
   public void testForInvalidAge() {
-    User john = new User("John", 17, Sex.MALE, "john@qwe.bar");
+    var john = new User("John", 17, Sex.MALE, "john@qwe.bar");
-    assertThrows(IllegalStateException.class, () -> {
+    assertThrows(
-      Validator.of(john).validate(User::getName, Objects::nonNull, "name cannot be null")
+        IllegalStateException.class,
-              .validate(User::getAge, age -> age > 21, "user is underaged")
+        () -> Validator.of(john)
-              .get();
+            .validate(User::getName, Objects::nonNull, "name cannot be null")
-    });
+            .validate(User::getAge, age -> age > 21, "user is underage")
+            .get()
+    );
   }
 
   @Test
   public void testForValid() {
-    User sarah = new User("Sarah", 42, Sex.FEMALE, "sarah@det.org");
+    var sarah = new User("Sarah", 42, Sex.FEMALE, "sarah@det.org");
-    User validated = Validator.of(sarah).validate(User::getName, Objects::nonNull, "name cannot be null")
+    var validated = Validator.of(sarah)
-        .validate(User::getAge, age -> age > 21, "user is underaged")
+        .validate(User::getName, Objects::nonNull, "name cannot be null")
+        .validate(User::getAge, age -> age > 21, "user is underage")
         .validate(User::getSex, sex -> sex == Sex.FEMALE, "user is not female")
         .validate(User::getEmail, email -> email.contains("@"), "email does not contain @ sign")
         .get();

monostate/src/main/java/com/iluwatar/monostate/App.java

@@ -30,7 +30,7 @@ package com.iluwatar.monostate;
  *
  * <p>In the following example, The {@link LoadBalancer} class represents the app's logic. It
  * contains a series of Servers, which can handle requests of type {@link Request}. Two instances of
- * LoadBalacer are created. When a request is made to a server via the first LoadBalancer the state
+ * LoadBalancer are created. When a request is made to a server via the first LoadBalancer the state
  * change in the first load balancer affects the second. So if the first LoadBalancer selects the
  * Server 1, the second LoadBalancer on a new request will select the Second server. If a third
  * LoadBalancer is created and a new request is made to it, then it will select the third server as
@@ -43,8 +43,8 @@ public class App {
    * @param args command line args
    */
   public static void main(String[] args) {
-    LoadBalancer loadBalancer1 = new LoadBalancer();
+    var loadBalancer1 = new LoadBalancer();
-    LoadBalancer loadBalancer2 = new LoadBalancer();
+    var loadBalancer2 = new LoadBalancer();
     loadBalancer1.serverRequest(new Request("Hello"));
     loadBalancer2.serverRequest(new Request("Hello World"));
   }

monostate/src/main/java/com/iluwatar/monostate/LoadBalancer.java

@@ -38,8 +38,8 @@ public class LoadBalancer {
   private static int lastServedId;
 
   static {
-    int id = 0;
+    var id = 0;
-    for (int port : new int[]{8080, 8081, 8082, 8083, 8084}) {
+    for (var port : new int[]{8080, 8081, 8082, 8083, 8084}) {
       SERVERS.add(new Server("localhost", port, ++id));
     }
   }
@@ -69,7 +69,7 @@ public class LoadBalancer {
     if (lastServedId >= SERVERS.size()) {
       lastServedId = 0;
     }
-    Server server = SERVERS.get(lastServedId++);
+    var server = SERVERS.get(lastServedId++);
     server.serve(request);
   }
 

monostate/src/test/java/com/iluwatar/monostate/AppTest.java

@@ -32,8 +32,7 @@ public class AppTest {
 
   @Test
   public void testMain() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 
 }

monostate/src/test/java/com/iluwatar/monostate/LoadBalancerTest.java

@@ -44,8 +44,8 @@ public class LoadBalancerTest {
 
   @Test
   public void testSameStateAmongstAllInstances() {
-    final LoadBalancer firstBalancer = new LoadBalancer();
+    final var firstBalancer = new LoadBalancer();
-    final LoadBalancer secondBalancer = new LoadBalancer();
+    final var secondBalancer = new LoadBalancer();
     firstBalancer.addServer(new Server("localhost", 8085, 6));
     // Both should have the same number of servers.
     assertEquals(firstBalancer.getNoOfServers(), secondBalancer.getNoOfServers());
@@ -55,18 +55,18 @@ public class LoadBalancerTest {
 
   @Test
   public void testServe() {
-    final Server server = mock(Server.class);
+    final var server = mock(Server.class);
     when(server.getHost()).thenReturn("testhost");
     when(server.getPort()).thenReturn(1234);
     doNothing().when(server).serve(any(Request.class));
 
-    final LoadBalancer loadBalancer = new LoadBalancer();
+    final var loadBalancer = new LoadBalancer();
     loadBalancer.addServer(server);
 
     verifyZeroInteractions(server);
 
-    final Request request = new Request("test");
+    final var request = new Request("test");
-    for (int i = 0; i < loadBalancer.getNoOfServers() * 2; i++) {
+    for (var i = 0; i < loadBalancer.getNoOfServers() * 2; i++) {
       loadBalancer.serverRequest(request);
     }
 

multiton/src/main/java/com/iluwatar/multiton/NazgulEnum.java

@@ -27,7 +27,13 @@ package com.iluwatar.multiton;
  * enum based multiton implementation.
  */
 public enum NazgulEnum {
-
+  KHAMUL,
-  KHAMUL, MURAZOR, DWAR, JI_INDUR, AKHORAHIL, HOARMURATH, ADUNAPHEL, REN, UVATHA
+  MURAZOR,
-
+  DWAR,
+  JI_INDUR,
+  AKHORAHIL,
+  HOARMURATH,
+  ADUNAPHEL,
+  REN,
+  UVATHA
 }

multiton/src/main/java/com/iluwatar/multiton/NazgulName.java

@@ -27,7 +27,13 @@ package com.iluwatar.multiton;
  * Each Nazgul has different {@link NazgulName}.
  */
 public enum NazgulName {
-
+  KHAMUL,
-  KHAMUL, MURAZOR, DWAR, JI_INDUR, AKHORAHIL, HOARMURATH, ADUNAPHEL, REN, UVATHA
+  MURAZOR,
-
+  DWAR,
+  JI_INDUR,
+  AKHORAHIL,
+  HOARMURATH,
+  ADUNAPHEL,
+  REN,
+  UVATHA
 }

multiton/src/test/java/com/iluwatar/multiton/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.multiton;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

multiton/src/test/java/com/iluwatar/multiton/NazgulEnumTest.java

@@ -39,10 +39,10 @@ class NazgulEnumTest {
    */
   @Test
   public void testTheSameObjectIsReturnedWithMultipleCalls() {
-    for (int i = 0; i < NazgulEnum.values().length; i++) {
+    for (var i = 0; i < NazgulEnum.values().length; i++) {
-      NazgulEnum instance1 = NazgulEnum.values()[i];
+      var instance1 = NazgulEnum.values()[i];
-      NazgulEnum instance2 = NazgulEnum.values()[i];
+      var instance2 = NazgulEnum.values()[i];
-      NazgulEnum instance3 = NazgulEnum.values()[i];
+      var instance3 = NazgulEnum.values()[i];
       assertSame(instance1, instance2);
       assertSame(instance1, instance3);
       assertSame(instance2, instance3);

multiton/src/test/java/com/iluwatar/multiton/NazgulTest.java

@@ -41,8 +41,8 @@ public class NazgulTest {
    */
   @Test
   public void testGetInstance() {
-    for (final NazgulName name : NazgulName.values()) {
+    for (final var name : NazgulName.values()) {
-      final Nazgul nazgul = Nazgul.getInstance(name);
+      final var nazgul = Nazgul.getInstance(name);
       assertNotNull(nazgul);
       assertSame(nazgul, Nazgul.getInstance(name));
       assertEquals(name, nazgul.getName());

mute-idiom/src/main/java/com/iluwatar/mute/App.java

@@ -25,7 +25,7 @@ package com.iluwatar.mute;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.sql.SQLException;
+import java.util.Optional;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -52,9 +52,8 @@ public class App {
    * Program entry point.
    *
    * @param args command line args.
-   * @throws Exception if any exception occurs
    */
-  public static void main(String[] args) throws Exception {
+  public static void main(String[] args) {
 
     useOfLoggedMute();
 
@@ -68,17 +67,17 @@ public class App {
    * exception occurs.
    */
   private static void useOfMute() {
-    ByteArrayOutputStream out = new ByteArrayOutputStream();
+    var out = new ByteArrayOutputStream();
     Mute.mute(() -> out.write("Hello".getBytes()));
   }
 
-  private static void useOfLoggedMute() throws SQLException {
+  private static void useOfLoggedMute() {
-    Resource resource = null;
+    Optional<Resource> resource = Optional.empty();
     try {
-      resource = acquireResource();
+      resource = Optional.of(acquireResource());
-      utilizeResource(resource);
+      utilizeResource(resource.get());
     } finally {
-      closeResource(resource);
+      resource.ifPresent(App::closeResource);
     }
   }
 
@@ -86,14 +85,14 @@ public class App {
    * All we can do while failed close of a resource is to log it.
    */
   private static void closeResource(Resource resource) {
-    Mute.loggedMute(() -> resource.close());
+    Mute.loggedMute(resource::close);
   }
 
-  private static void utilizeResource(Resource resource) throws SQLException {
+  private static void utilizeResource(Resource resource) {
     LOGGER.info("Utilizing acquired resource: {}", resource);
   }
 
-  private static Resource acquireResource() throws SQLException {
+  private static Resource acquireResource() {
     return new Resource() {
 
       @Override

mute-idiom/src/test/java/com/iluwatar/mute/AppTest.java

@@ -27,12 +27,11 @@ import org.junit.jupiter.api.Test;
 
 /**
  * Tests that Mute idiom example runs without errors.
- *
  */
 public class AppTest {
 
   @Test
-  public void test() throws Exception {
+  public void test() {
-    App.main(null);
+    App.main(new String[]{});
   }
 }

mute-idiom/src/test/java/com/iluwatar/mute/MuteTest.java

@@ -23,17 +23,15 @@
 
 package com.iluwatar.mute;
 
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
 import org.junit.jupiter.api.Test;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.io.ByteArrayOutputStream;
-import java.io.IOException;
-import java.io.PrintStream;
-
-import static org.junit.jupiter.api.Assertions.assertThrows;
-import static org.junit.jupiter.api.Assertions.assertTrue;
-
 /**
  * Test for the mute-idiom pattern
  */
@@ -50,9 +48,7 @@ public class MuteTest {
 
   @Test
   public void muteShouldRethrowUnexpectedExceptionAsAssertionError() {
-    assertThrows(AssertionError.class, () -> {
+    assertThrows(AssertionError.class, () -> Mute.mute(this::methodThrowingException));
-      Mute.mute(this::methodThrowingException);
-    });
   }
 
   @Test
@@ -62,7 +58,7 @@ public class MuteTest {
 
   @Test
   public void loggedMuteShouldLogExceptionTraceBeforeSwallowingIt() {
-    ByteArrayOutputStream stream = new ByteArrayOutputStream();
+    var stream = new ByteArrayOutputStream();
     System.setErr(new PrintStream(stream));
 
     Mute.loggedMute(this::methodThrowingException);

mutex/src/main/java/com/iluwatar/mutex/App.java

@@ -38,10 +38,10 @@ public class App {
    * main method.
    */
   public static void main(String[] args) {
-    Mutex mutex = new Mutex();
+    var mutex = new Mutex();
-    Jar jar = new Jar(1000, mutex);
+    var jar = new Jar(1000, mutex);
-    Thief peter = new Thief("Peter", jar);
+    var peter = new Thief("Peter", jar);
-    Thief john = new Thief("John", jar);
+    var john = new Thief("John", jar);
     peter.start();
     john.start();
   }

mutex/src/main/java/com/iluwatar/mutex/Jar.java

@@ -48,7 +48,7 @@ public class Jar {
    * Method for a thief to take a bean.
    */
   public boolean takeBean() {
-    boolean success = false;
+    var success = false;
     try {
       lock.acquire();
       success = beans > 0;

mutex/src/main/java/com/iluwatar/mutex/Thief.java

@@ -54,7 +54,7 @@ public class Thief extends Thread {
    */
   @Override
   public void run() {
-    int beans = 0;
+    var beans = 0;
 
     while (jar.takeBean()) {
       beans = beans + 1;

mutex/src/test/java/com/iluwatar/mutex/AppTest.java

@@ -25,15 +25,12 @@ package com.iluwatar.mutex;
 
 import org.junit.jupiter.api.Test;
 
-import java.io.IOException;
-
 /**
  * Application Test Entrypoint
  */
 public class AppTest {
   @Test
-  public void test() throws IOException {
+  public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

mutex/src/test/java/com/iluwatar/mutex/JarTest.java

@@ -23,10 +23,11 @@
 
 package com.iluwatar.mutex;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.stream.IntStream;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
 
 /**
  * Test case for taking beans from a Jar
@@ -35,12 +36,10 @@ public class JarTest {
 
   @Test
   public void testTakeBeans() {
-    Mutex mutex = new Mutex();
+    var mutex = new Mutex();
-    Jar jar = new Jar(10, mutex);
+    var jar = new Jar(10, mutex);
-    for (int i = 0; i < 10; i++) {
+    IntStream.range(0, 10).mapToObj(i -> jar.takeBean()).forEach(Assertions::assertTrue);
-      assertTrue(jar.takeBean());
-    }
     assertFalse(jar.takeBean());
   }
 
-}
+}

mutex/src/test/java/com/iluwatar/mutex/MutexTest.java

@@ -23,12 +23,12 @@
 
 package com.iluwatar.mutex;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.fail;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Test case for acquiring and releasing a Mutex
  */
@@ -36,7 +36,7 @@ public class MutexTest {
 
   @Test
   public void acquireReleaseTest() {
-    Mutex mutex = new Mutex();
+    var mutex = new Mutex();
     assertNull(mutex.getOwner());
     try {
       mutex.acquire();