Java 11 migrate c-d (remaining) (#1111)

* Moves converter pattern to Java 11

* Moves cqrs pattern to Java 11

* Moves dao pattern to Java 11

* Moves data-bus pattern to Java 11

* Moves data-locality pattern to Java 11

* Moves data-mapper pattern to Java 11

* Moves data-transfer-object pattern to Java 11

* Moves decorator pattern to Java 11

* Moves delegation pattern to Java 11

* Moves dependency-injection to Java 11

* Moves dirty-flag to Java 11

* Moves double-buffer to Java 11

* Moves double-checked-locking to Java 11

* Moves double-dispatch to Java 11

* Corrects with changes thats breaking test cases

data-mapper/src/main/java/com/iluwatar/datamapper/App.java

@@ -23,7 +23,6 @@
 
 package com.iluwatar.datamapper;
 
-import java.util.Optional;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -51,10 +50,10 @@ public final class App {
   public static void main(final String... args) {
 
     /* Create new data mapper for type 'first' */
-    final StudentDataMapper mapper = new StudentDataMapperImpl();
+    final var mapper = new StudentDataMapperImpl();
 
     /* Create new student */
-    Student student = new Student(1, "Adam", 'A');
+    var student = new Student(1, "Adam", 'A');
 
     /* Add student in respectibe store */
     mapper.insert(student);
@@ -62,7 +61,7 @@ public final class App {
     log.debug(STUDENT_STRING + student + ", is inserted");
 
     /* Find this student */
-    final Optional<Student> studentToBeFound = mapper.find(student.getStudentId());
+    final var studentToBeFound = mapper.find(student.getStudentId());
 
     log.debug(STUDENT_STRING + studentToBeFound + ", is searched");
 

data-mapper/src/main/java/com/iluwatar/datamapper/Student.java

@@ -85,7 +85,7 @@ public final class Student implements Serializable {
       isEqual = true;
     } else if (inputObject != null && getClass() == inputObject.getClass()) {
 
-      final Student inputStudent = (Student) inputObject;
+      final var inputStudent = (Student) inputObject;
 
       /* If student id matched */
       if (this.getStudentId() == inputStudent.getStudentId()) {

data-mapper/src/main/java/com/iluwatar/datamapper/StudentDataMapperImpl.java

@@ -37,71 +37,36 @@ public final class StudentDataMapperImpl implements StudentDataMapper {
 
   @Override
   public Optional<Student> find(int studentId) {
-
-    /* Compare with existing students */
-    for (final Student student : this.getStudents()) {
-
-      /* Check if student is found */
-      if (student.getStudentId() == studentId) {
-
-        return Optional.of(student);
-      }
-    }
-
-    /* Return empty value */
-    return Optional.empty();
+    return this.getStudents().stream().filter(x -> x.getStudentId() == studentId).findFirst();
   }
 
   @Override
   public void update(Student studentToBeUpdated) throws DataMapperException {
-
-
-    /* Check with existing students */
-    if (this.getStudents().contains(studentToBeUpdated)) {
-
-      /* Get the index of student in list */
-      final int index = this.getStudents().indexOf(studentToBeUpdated);
-
-      /* Update the student in list */
-      this.getStudents().set(index, studentToBeUpdated);
-
-    } else {
-
-      /* Throw user error after wrapping in a runtime exception */
-      throw new DataMapperException("Student [" + studentToBeUpdated.getName() + "] is not found");
-    }
+    String name = studentToBeUpdated.getName();
+    Integer index = Optional.of(studentToBeUpdated)
+        .map(Student::getStudentId)
+        .flatMap(this::find)
+        .map(students::indexOf)
+        .orElseThrow(() -> new DataMapperException("Student [" + name + "] is not found"));
+    students.set(index, studentToBeUpdated);
   }
 
   @Override
   public void insert(Student studentToBeInserted) throws DataMapperException {
-
-    /* Check with existing students */
-    if (!this.getStudents().contains(studentToBeInserted)) {
-
-      /* Add student in list */
-      this.getStudents().add(studentToBeInserted);
-
-    } else {
-
-      /* Throw user error after wrapping in a runtime exception */
-      throw new DataMapperException("Student already [" + studentToBeInserted
-          .getName() + "] exists");
+    Optional<Student> student = find(studentToBeInserted.getStudentId());
+    if (student.isPresent()) {
+      String name = studentToBeInserted.getName();
+      throw new DataMapperException("Student already [" + name + "] exists");
     }
+
+    students.add(studentToBeInserted);
   }
 
   @Override
   public void delete(Student studentToBeDeleted) throws DataMapperException {
-
-    /* Check with existing students */
-    if (this.getStudents().contains(studentToBeDeleted)) {
-
-      /* Delete the student from list */
-      this.getStudents().remove(studentToBeDeleted);
-
-    } else {
-
-      /* Throw user error after wrapping in a runtime exception */
-      throw new DataMapperException("Student [" + studentToBeDeleted.getName() + "] is not found");
+    if (!students.remove(studentToBeDeleted)) {
+      String name = studentToBeDeleted.getName();
+      throw new DataMapperException("Student [" + name + "] is not found");
     }
   }
 

data-mapper/src/test/java/com/iluwatar/datamapper/AppTest.java

@@ -32,7 +32,6 @@ public final class AppTest {
 
   @Test
   public void test() {
-    final String[] args = {};
-    App.main(args);
+    App.main();
   }
 }

data-mapper/src/test/java/com/iluwatar/datamapper/DataMapperTest.java

@@ -23,11 +23,11 @@
 
 package com.iluwatar.datamapper;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * The Data Mapper (DM) is a layer of software that separates the in-memory objects from the
  * database. Its responsibility is to transfer data between the two and also to isolate them from
@@ -46,11 +46,11 @@ public class DataMapperTest {
   public void testFirstDataMapper() {
 
     /* Create new data mapper of first type */
-    final StudentDataMapper mapper = new StudentDataMapperImpl();
+    final var mapper = new StudentDataMapperImpl();
 
     /* Create new student */
-    int studentId = 1;
-    Student student = new Student(studentId, "Adam", 'A');
+    var studentId = 1;
+    var student = new Student(studentId, "Adam", 'A');
 
     /* Add student in respectibe db */
     mapper.insert(student);
@@ -59,7 +59,7 @@ public class DataMapperTest {
     assertEquals(studentId, mapper.find(student.getStudentId()).get().getStudentId());
 
     /* Update existing student object */
-    String updatedName = "AdamUpdated";
+    var updatedName = "AdamUpdated";
     student = new Student(student.getStudentId(), updatedName, 'A');
 
     /* Update student in respectibe db */

data-mapper/src/test/java/com/iluwatar/datamapper/StudentTest.java

@@ -23,12 +23,10 @@
 
 package com.iluwatar.datamapper;
 
-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.assertNotEquals;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
 
 /**
  * Tests {@link Student}.
@@ -36,8 +34,8 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 public final class StudentTest {
 
   /**
-   * This API tests the equality behaviour of Student object
-   * Object Equality should work as per logic defined in equals method
+   * This API tests the equality behaviour of Student object Object Equality should work as per
+   * logic defined in equals method
    *
    * @throws Exception if any execution error during test
    */
@@ -45,9 +43,9 @@ public final class StudentTest {
   public void testEquality() throws Exception {
 
     /* Create some students */
-    final Student firstStudent = new Student(1, "Adam", 'A');
-    final Student secondStudent = new Student(2, "Donald", 'B');
-    final Student secondSameStudent = new Student(2, "Donald", 'B');
+    final var firstStudent = new Student(1, "Adam", 'A');
+    final var secondStudent = new Student(2, "Donald", 'B');
+    final var secondSameStudent = new Student(2, "Donald", 'B');
 
     /* Check equals functionality: should return 'true' */
     assertEquals(firstStudent, firstStudent);