Code improvements.

thread-pool/src/main/java/com/iluwatar/CoffeeMakingTask.java

@@ -7,7 +7,7 @@ package com.iluwatar;
  */
 public class CoffeeMakingTask extends Task {
 
-	private static int TIME_PER_CUP = 300;
+	private static final int TIME_PER_CUP = 300;
 	
 	public CoffeeMakingTask(int numCups) {
 		super(numCups * TIME_PER_CUP);

thread-pool/src/main/java/com/iluwatar/PotatoPeelingTask.java

@@ -7,7 +7,7 @@ package com.iluwatar;
  */
 public class PotatoPeelingTask extends Task {
 
-	private static int TIME_PER_POTATO = 500;
+	private static final int TIME_PER_POTATO = 500;
 	
 	public PotatoPeelingTask(int numPotatoes) {
 		super(numPotatoes * TIME_PER_POTATO);

thread-pool/src/main/java/com/iluwatar/Task.java

@@ -9,10 +9,10 @@ public abstract class Task {
 
 	private static int nextId = 1;
 	
-	private int id;
-	private int timeMs;
+	private final int id;
+	private final int timeMs;
 	
-	public Task(int timeMs) {
+	public Task(final int timeMs) {
 		this.id = nextId++;
 		this.timeMs = timeMs;
 	}

thread-pool/src/main/java/com/iluwatar/Worker.java

@@ -7,9 +7,9 @@ package com.iluwatar;
  */
 public class Worker implements Runnable {
 	
-	private Task task;
+	private final Task task;
 
-	public Worker(Task task) {
+	public Worker(final Task task) {
 		this.task = task;
 	}