Resolves checkstyle errors for callback, chain, circuit-breaker (#1060)

* Reduces checkstyle errors in callback

* Reduces checkstyle errors in chain

* Reduces checkstyle errors in circuit-breaker

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

@@ -23,16 +23,14 @@
 
 package com.iluwatar.callback;
 
-import org.slf4j.Logger;
-
 import static org.slf4j.LoggerFactory.getLogger;
 
+import org.slf4j.Logger;
+
 /**
- *
+ * Callback pattern is more native for functional languages where functions are treated as
- * Callback pattern is more native for functional languages where functions are
+ * first-class citizens. Prior to Java 8 callbacks can be simulated using simple (alike command)
- * treated as first-class citizens. Prior to Java 8 callbacks can be simulated
+ * interfaces.
- * using simple (alike command) interfaces.
- *
  */
 public final class App {
 
@@ -42,7 +40,7 @@ public final class App {
   }
 
   /**
-   * Program entry point
+   * Program entry point.
    */
   public static void main(final String[] args) {
     Task task = new SimpleTask();

callback/src/main/java/com/iluwatar/callback/Callback.java

@@ -24,9 +24,7 @@
 package com.iluwatar.callback;
 
 /**
- *
+ * Callback interface.
- * Callback interface
- *
  */
 public interface Callback {
 

callback/src/main/java/com/iluwatar/callback/LambdasApp.java

@@ -23,24 +23,23 @@
 
 package com.iluwatar.callback;
 
-import org.slf4j.Logger;
-
 import static org.slf4j.LoggerFactory.getLogger;
 
+import org.slf4j.Logger;
+
 /**
- *
+ * This example generates the exact same output as {@link App} however the callback has been defined
- * This example generates the exact same output as {@link App} however the
+ * as a Lambdas expression.
- * callback has been defined as a Lambdas expression.
- *
  */
 public final class LambdasApp {
 
   private static final Logger LOGGER = getLogger(LambdasApp.class);
 
-  private LambdasApp() { }
+  private LambdasApp() {
+  }
 
   /**
-   * Program entry point
+   * Program entry point.
    */
   public static void main(final String[] args) {
     Task task = new SimpleTask();

callback/src/main/java/com/iluwatar/callback/SimpleTask.java

@@ -23,14 +23,12 @@
 
 package com.iluwatar.callback;
 
-import org.slf4j.Logger;
-
 import static org.slf4j.LoggerFactory.getLogger;
 
+import org.slf4j.Logger;
+
 /**
- *
+ * Implementation of task that need to be executed.
- * Implementation of task that need to be executed
- *
  */
 public final class SimpleTask extends Task {
 
@@ -39,6 +37,6 @@ public final class SimpleTask extends Task {
   @Override
   public void execute() {
     LOGGER.info("Perform some important activity and after call the"
-            + " callback method.");
+        + " callback method.");
   }
 }

callback/src/main/java/com/iluwatar/callback/Task.java

@@ -24,14 +24,12 @@
 package com.iluwatar.callback;
 
 /**
- *
+ * Template-method class for callback hook execution.
- * Template-method class for callback hook execution
- *
  */
 public abstract class Task {
 
   /**
-   * Execute with callback
+   * Execute with callback.
    */
   final void executeWith(final Callback callback) {
     execute();

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

@@ -24,23 +24,21 @@
 package com.iluwatar.chain;
 
 /**
- * 
  * The Chain of Responsibility pattern is a design pattern consisting of command objects and a
  * series of processing objects. Each processing object contains logic that defines the types of
  * command objects that it can handle; the rest are passed to the next processing object in the
  * chain. A mechanism also exists for adding new processing objects to the end of this chain.
- * <p>
+ *
- * In this example we organize the request handlers ({@link RequestHandler}) into a chain where each
+ * <p>In this example we organize the request handlers ({@link RequestHandler}) into a chain where
- * handler has a chance to act on the request on its turn. Here the king ({@link OrcKing}) makes
+ * each handler has a chance to act on the request on its turn. Here the king ({@link OrcKing})
- * requests and the military orcs ({@link OrcCommander}, {@link OrcOfficer}, {@link OrcSoldier})
+ * makes requests and the military orcs ({@link OrcCommander}, {@link OrcOfficer}, {@link
- * form the handler chain.
+ * OrcSoldier}) form the handler chain.
- * 
  */
 public class App {
 
   /**
-   * Program entry point
+   * Program entry point.
-   * 
+   *
    * @param args command line args
    */
   public static void main(String[] args) {

chain/src/main/java/com/iluwatar/chain/OrcCommander.java

@@ -24,9 +24,7 @@
 package com.iluwatar.chain;
 
 /**
- * 
+ * OrcCommander.
- * OrcCommander
- *
  */
 public class OrcCommander extends RequestHandler {
 

chain/src/main/java/com/iluwatar/chain/OrcKing.java

@@ -24,9 +24,7 @@
 package com.iluwatar.chain;
 
 /**
- * 
  * OrcKing makes requests that are handled by the chain.
- * 
  */
 public class OrcKing {
 

chain/src/main/java/com/iluwatar/chain/OrcOfficer.java

@@ -24,9 +24,7 @@
 package com.iluwatar.chain;
 
 /**
- * 
+ * OrcOfficer.
- * OrcOfficer
- *
  */
 public class OrcOfficer extends RequestHandler {
 

chain/src/main/java/com/iluwatar/chain/OrcSoldier.java

@@ -24,9 +24,7 @@
 package com.iluwatar.chain;
 
 /**
- * 
+ * OrcSoldier.
- * OrcSoldier
- *
  */
 public class OrcSoldier extends RequestHandler {
 

chain/src/main/java/com/iluwatar/chain/Request.java

@@ -26,24 +26,24 @@ package com.iluwatar.chain;
 import java.util.Objects;
 
 /**
- * Request
+ * Request.
  */
 public class Request {
 
   /**
    * The type of this request, used by each item in the chain to see if they should or can handle
-   * this particular request
+   * this particular request.
    */
   private final RequestType requestType;
 
   /**
-   * A description of the request
+   * A description of the request.
    */
   private final String requestDescription;
 
   /**
    * Indicates if the request is handled or not. A request can only switch state from unhandled to
-   * handled, there's no way to 'unhandle' a request
+   * handled, there's no way to 'unhandle' a request.
    */
   private boolean handled;
 
@@ -59,7 +59,7 @@ public class Request {
   }
 
   /**
-   * Get a description of the request
+   * Get a description of the request.
    *
    * @return A human readable description of the request
    */
@@ -69,7 +69,7 @@ public class Request {
 
   /**
    * Get the type of this request, used by each person in the chain of command to see if they should
-   * or can handle this particular request
+   * or can handle this particular request.
    *
    * @return The request type
    */
@@ -78,14 +78,14 @@ public class Request {
   }
 
   /**
-   * Mark the request as handled
+   * Mark the request as handled.
    */
   public void markHandled() {
     this.handled = true;
   }
 
   /**
-   * Indicates if this request is handled or not
+   * Indicates if this request is handled or not.
    *
    * @return <tt>true</tt> when the request is handled, <tt>false</tt> if not
    */

chain/src/main/java/com/iluwatar/chain/RequestHandler.java

@@ -27,9 +27,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * 
+ * RequestHandler.
- * RequestHandler
- *
  */
 public abstract class RequestHandler {
 
@@ -42,7 +40,7 @@ public abstract class RequestHandler {
   }
 
   /**
-   * Request handler
+   * Request handler.
    */
   public void handleRequest(Request req) {
     if (next != null) {

chain/src/main/java/com/iluwatar/chain/RequestType.java

@@ -24,9 +24,7 @@
 package com.iluwatar.chain;
 
 /**
- * 
+ * RequestType enumeration.
- * RequestType enumeration
- *
  */
 public enum RequestType {
 

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/App.java

@@ -28,42 +28,39 @@ import org.slf4j.LoggerFactory;
 
 /**
  * <p>
- * The intention of the Circuit Builder pattern is to handle remote failures 
+ * The intention of the Circuit Builder pattern is to handle remote failures robustly, which is to
- * robustly, which is to mean that if a service is dependant on n number of
+ * mean that if a service is dependant on n number of other services, and m of them fail, we should
- * other services, and m of them fail, we should be able to recover from that
+ * be able to recover from that failure by ensuring that the user can still use the services that
- * failure by ensuring that the user can still use the services that are actually
+ * are actually functional, and resources are not tied up by uselessly by the services which are not
- * functional, and resources are not tied up by uselessly by the services which
+ * working. However, we should also be able to detect when any of the m failing services become
- * are not working. However, we should also be able to detect when any of the m
+ * operational again, so that we can use it
- * failing services become operational again, so that we can use it
  * </p>
  * <p>
- * In this example, the circuit breaker pattern is demonstrated by using two services:
+ * In this example, the circuit breaker pattern is demonstrated by using two services: {@link
- * {@link MonitoringService} and {@link DelayedService}. The monitoring service
+ * MonitoringService} and {@link DelayedService}. The monitoring service is responsible for calling
- * is responsible for calling two services: a local service and a remote service {@link DelayedService}
+ * two services: a local service and a remote service {@link DelayedService} , and by using the
- * , and by using the circuit breaker construction we ensure that if the call to
+ * circuit breaker construction we ensure that if the call to remote service is going to fail, we
- * remote service is going to fail, we are going to save our resources and not make the 
+ * are going to save our resources and not make the function call at all, by wrapping our call to
- * function call at all, by wrapping our call to the remote service in the circuit
+ * the remote service in the circuit breaker object.
- * breaker object.
  * </p>
  * <p>
- * This works as follows: The {@link CircuitBreaker} object can be in one of three
+ * This works as follows: The {@link CircuitBreaker} object can be in one of three states:
- * states: <b>Open</b>, <b>Closed</b> and <b>Half-Open</b>, which represents the real
+ * <b>Open</b>, <b>Closed</b> and <b>Half-Open</b>, which represents the real world circuits. If the
- * world circuits. If the state is closed (initial), we assume everything is alright
+ * state is closed (initial), we assume everything is alright and perform the function call.
- * and perform the function call. However, every time the call fails, we note it
+ * However, every time the call fails, we note it and once it crosses a threshold, we set the state
- * and once it crosses a threshold, we set the state to Open, preventing any further
+ * to Open, preventing any further calls to the remote server. Then, after a certain retry period
- * calls to the remote server. Then, after a certain retry period (during which we
+ * (during which we expect thee service to recover), we make another call to the remote server and
- * expect thee service to recover), we make another call to the remote server and
+ * this state is called the Half-Open state, where it stays till the service is down, and once it
- * this state is called the Half-Open state, where it stays till the service is down,
+ * recovers, it goes back to the closed state and the cycle continues.
- * and once it recovers, it goes back to the closed state and the cycle continues.
  * </p>
  */
 public class App {
-   
+
   private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
-    
+
-   /**
+  /**
-   * Program entry point
+   * Program entry point.
-   * 
+   *
    * @param args command line args
    */
   @SuppressWarnings("squid:S2189")
@@ -71,14 +68,14 @@ public class App {
     //Create an object of monitoring service which makes both local and remote calls
     var obj = new MonitoringService();
     //Set the circuit Breaker parameters
-    var circuitBreaker = new CircuitBreaker(3000, 1, 2000 * 1000 * 1000); 
+    var circuitBreaker = new CircuitBreaker(3000, 1, 2000 * 1000 * 1000);
     var serverStartTime = System.nanoTime();
     while (true) {
       LOGGER.info(obj.localResourceResponse());
       LOGGER.info(obj.remoteResourceResponse(circuitBreaker, serverStartTime));
       LOGGER.info(circuitBreaker.getState());
       try {
-        Thread.sleep(5 * 1000); 
+        Thread.sleep(5 * 1000);
       } catch (InterruptedException e) {
         LOGGER.error(e.getMessage());
       }

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/CircuitBreaker.java

@@ -24,7 +24,7 @@
 package com.iluwatar.circuitbreaker;
 
 /**
- * The circuit breaker class with all configurations
+ * The circuit breaker class with all configurations.
  */
 public class CircuitBreaker {
   private final long timeout;
@@ -36,27 +36,31 @@ public class CircuitBreaker {
   private final long futureTime = 1000 * 1000 * 1000 * 1000;
 
   /**
-   * Constructor to create an instance of Circuit Breaker
+   * Constructor to create an instance of Circuit Breaker.
-   * @param timeout Timeout for the API request. Not necessary for this simple example
+   *
-   * @param failureThreshold Number of failures we receive from the depended service before changing state to 'OPEN'
+   * @param timeout          Timeout for the API request. Not necessary for this simple example
-   * @param retryTimePeriod Time period after which a new request is made to remote service for status check.
+   * @param failureThreshold Number of failures we receive from the depended service before changing
+   *                         state to 'OPEN'
+   * @param retryTimePeriod  Time period after which a new request is made to remote service for
+   *                         status check.
    */
   CircuitBreaker(long timeout, int failureThreshold, long retryTimePeriod) {
     // We start in a closed state hoping that everything is fine
     this.state = State.CLOSED;
     this.failureThreshold = failureThreshold;
-    // Timeout for the API request. Used to break the calls made to remote resource if it exceeds the limit
+    // Timeout for the API request.
+    // Used to break the calls made to remote resource if it exceeds the limit
     this.timeout = timeout;
     this.retryTimePeriod = retryTimePeriod;
     //An absurd amount of time in future which basically indicates the last failure never happened
     this.lastFailureTime = System.nanoTime() + futureTime;
     this.failureCount = 0;
   }
-    
+
   //Reset everything to defaults
   private void reset() {
     this.failureCount = 0;
-    this.lastFailureTime = System.nanoTime() + futureTime; 
+    this.lastFailureTime = System.nanoTime() + futureTime;
     this.state = State.CLOSED;
   }
 
@@ -64,7 +68,7 @@ public class CircuitBreaker {
     failureCount = failureCount + 1;
     this.lastFailureTime = System.nanoTime();
   }
-    
+
   protected void setState() {
     if (failureCount > failureThreshold) { //Then something is wrong with remote service
       if ((System.nanoTime() - lastFailureTime) > retryTimePeriod) {
@@ -79,23 +83,28 @@ public class CircuitBreaker {
       state = State.CLOSED;
     }
   }
-    
+
   public String getState() {
     return state.name();
   }
-  
+
   /**
-   * Break the circuit beforehand if it is known service is down
+   * Break the circuit beforehand if it is known service is down Or connect the circuit manually if
-   * Or connect the circuit manually if service comes online before expected
+   * service comes online before expected.
+   *
    * @param state State at which circuit is in
    */
   public void setStateForBypass(State state) {
     this.state = state;
   }
-   
+
   /**
-   * @param serviceToCall The name of the service in String. Can be changed to data URLs in case of web applications
+   * Executes service call.
-   * @param serverStartTime Time at which actual server was started which makes calls to this service
+   *
+   * @param serviceToCall   The name of the service in String. Can be changed to data URLs in case
+   *                        of web applications
+   * @param serverStartTime Time at which actual server was started which makes calls to this
+   *                        service
    * @return Value from the remote resource, stale response or a custom exception
    */
   public String call(String serviceToCall, long serverStartTime) throws Exception {
@@ -104,7 +113,7 @@ public class CircuitBreaker {
       // return  cached response if no the circuit is in OPEN state
       return "This is stale response from API";
     } else {
-        // Make the API request if the circuit is not OPEN
+      // Make the API request if the circuit is not OPEN
       if (serviceToCall.equals("delayedService")) {
         var delayedService = new DelayedService(20);
         var response = delayedService.response(serverStartTime);

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/DelayedService.java

@@ -24,14 +24,15 @@
 package com.iluwatar.circuitbreaker;
 
 /**
-* This simulates the remote service
+ * This simulates the remote service It responds only after a certain timeout period (default set to
-* It responds only after a certain timeout period (default set to 20 seconds)
+ * 20 seconds).
-*/
+ */
 public class DelayedService {
   private final int delay;
 
   /**
-   * Constructor to create an instance of DelayedService, which is down for first few seconds
+   * Constructor to create an instance of DelayedService, which is down for first few seconds.
+   *
    * @param delay the delay after which service would behave properly, in seconds
    */
   public DelayedService(int delay) {
@@ -43,7 +44,10 @@ public class DelayedService {
   }
 
   /**
-   * @param serverStartTime Time at which actual server was started which makes calls to this service
+   * Responds based on delay, current time and server start time if the service is down / working.
+   *
+   * @param serverStartTime Time at which actual server was started which makes calls to this
+   *                        service
    * @return The state of the service
    */
   public String response(long serverStartTime) {

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/MonitoringService.java

@@ -24,8 +24,8 @@
 package com.iluwatar.circuitbreaker;
 
 /**
- * The service class which makes local and remote calls
+ * The service class which makes local and remote calls Uses {@link CircuitBreaker} object to ensure
- * Uses {@link CircuitBreaker} object to ensure remote calls don't use up resources
+ * remote calls don't use up resources.
  */
 public class MonitoringService {
 
@@ -35,9 +35,11 @@ public class MonitoringService {
   }
 
   /**
-   * Try to get result from remote server
+   * Try to get result from remote server.
-   * @param circuitBreaker The circuitBreaker object with all parameters
+   *
-   * @param serverStartTime Time at which actual server was started which makes calls to this service
+   * @param circuitBreaker  The circuitBreaker object with all parameters
+   * @param serverStartTime Time at which actual server was started which makes calls to this
+   *                        service
    * @return result from the remote response or exception raised by it.
    */
   public String remoteResourceResponse(CircuitBreaker circuitBreaker, long serverStartTime) {

circuit-breaker/src/main/java/com/iluwatar/circuitbreaker/State.java

@@ -24,10 +24,10 @@
 package com.iluwatar.circuitbreaker;
 
 /**
- * Enumeration for states the circuit breaker could be in
+ * Enumeration for states the circuit breaker could be in.
  */
 public enum State {
-        CLOSED,
+  CLOSED,
-        OPEN,
+  OPEN,
-        HALF_OPEN
+  HALF_OPEN
 }