ThreadPool class using non-concurrent data structures

named by SynchronizedTaskQueue

.gitignore

+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### IntelliJ IDEA ###
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+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
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+
+### Mac OS ###
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.idea/misc.xml

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.idea/workspace.xml

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+      <change afterPath="$PROJECT_DIR$/src/main/java/PoolThreadRunnable.java" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/src/main/java/SynchronizedTaskQueue.java" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/src/main/java/ThreadPool.java" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/src/test/java/TestThreadPool.java" afterDir="false" />
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+    <option name="showLibraryContents" value="true" />
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+  <component name="PropertiesComponent">{
+  &quot;keyToString&quot;: {
+    &quot;RunOnceActivity.OpenProjectViewOnStart&quot;: &quot;true&quot;,
+    &quot;RunOnceActivity.ShowReadmeOnStart&quot;: &quot;true&quot;,
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+  <component name="RunManager">
+    <configuration name="TestThreadPool" type="Application" factoryName="Application" temporary="true" nameIsGenerated="true">
+      <option name="MAIN_CLASS_NAME" value="TestThreadPool" />
+      <module name="SynchronizedThreadPoolHW" />
+      <method v="2">
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+      </method>
+    </configuration>
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pom.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<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">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>org.example</groupId>
+    <artifactId>SynchronizedThreadPoolHW</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>17</maven.compiler.source>
+        <maven.compiler.target>17</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>
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src/main/java/PoolThreadRunnable.java

+import java.util.concurrent.ThreadFactory;
+
+public class PoolThreadRunnable implements Runnable {
+    // PoolThreadRunnable class represent the task will execute
+    private Thread thread = null;
+    private SynchronizedTaskQueue taskQueue = null;
+    private boolean isStopped = false;
+
+    public PoolThreadRunnable(SynchronizedTaskQueue queue){
+        taskQueue = queue;
+    }
+
+    public void run(){
+        this.thread = Thread.currentThread();
+        while(!isStopped()){
+            try{
+                Runnable runnable = (Runnable) taskQueue.removeTask();
+                runnable.run();
+            } catch(Exception e){
+                //log or otherwise report exception,
+                //but keep pool thread alive.
+            }
+        }
+    }
+
+    public synchronized void doStop(){
+        isStopped = true;
+        //break pool thread out of dequeue() call.
+        if (this.thread != null) {
+            this.thread.interrupt();
+        }
+    }
+
+    public synchronized boolean isStopped(){
+        return isStopped;
+    }
+}

src/main/java/SynchronizedTaskQueue.java

+//import java.util.LinkedList;
+//import java.util.Queue;
+//
+//public class SynchronizedTaskQueue {
+//
+//    private Queue<Object> taskQueue;
+//
+//    public SynchronizedTaskQueue() {
+//        this.taskQueue = new LinkedList<>();
+//    }
+//
+//    public synchronized void addTask(Object task) {
+//        taskQueue.add(task);
+//    }
+//
+//    public synchronized Object removeTask() {
+//        return taskQueue.remove();
+//    }
+//
+//    public synchronized Object peekTask() {
+//        return taskQueue.peek();
+//    }
+//
+//    // Add other methods as needed, and synchronize them as well
+//}
+
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+
+public class SynchronizedTaskQueue {
+    // SynchronizedTaskQueue class represent BlockingQueue but Synchronization was made manually using   non-concurrent data structures
+    private Deque<Object> taskQueue;
+    private int capacity;
+
+    public SynchronizedTaskQueue() {
+        this.taskQueue = new ArrayDeque<>();
+        this.capacity = Integer.MAX_VALUE; // Default capacity
+    }
+
+    public SynchronizedTaskQueue(int capacity) {
+        this.taskQueue = new ArrayDeque<>();
+        this.capacity = capacity;
+    }
+
+    public synchronized void addTask(Object task) {
+        if (taskQueue.size() >= capacity) {
+            throw new IllegalStateException("Queue is full");
+        }
+        taskQueue.add(task);
+    }
+
+    public synchronized Object removeTask() {
+        return taskQueue.remove();
+    }
+
+    public synchronized Object peekTask() {
+        return taskQueue.peek();
+    }
+}
+

src/main/java/ThreadPool.java

+import java.util.List;
+import java.util.ArrayList;
+
+public class ThreadPool {
+    // ThreadPool class
+    private SynchronizedTaskQueue taskQueue = null;
+    private List<PoolThreadRunnable> runnables = new ArrayList<>();
+    private boolean isStopped = false;
+
+    public ThreadPool(int noOfThreads, int maxNoOfTasks){
+        taskQueue = new SynchronizedTaskQueue(maxNoOfTasks);
+
+        for(int i=0; i<noOfThreads; i++){
+            PoolThreadRunnable poolThreadRunnable =
+                    new PoolThreadRunnable(taskQueue);
+
+            runnables.add(poolThreadRunnable);
+        }
+        for(PoolThreadRunnable runnable : runnables){
+            new Thread(runnable).start();
+        }
+    }
+
+    public void execute(Runnable task) throws Exception{
+        if(this.isStopped) throw
+                new IllegalStateException("ThreadPool is stopped");
+
+        this.taskQueue.addTask(task);
+    }
+
+    public void stop(){
+        this.isStopped = true;
+        for(PoolThreadRunnable runnable : runnables){
+            runnable.doStop();
+        }
+    }
+
+    public void waitUntilAllTasksFinished() {
+        while(this.taskQueue.peekTask() != null) {
+            try {
+                Thread.sleep(1);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+        }
+    }
+}

src/test/java/TestThreadPool.java

+import java.util.ArrayList;
+import java.util.List;
+
+public class TestThreadPool {
+
+    public static void main(String[] args) {
+        // Create Integers that represent number of tasks, max number of tasks and real number of tasks
+        int noOfthreads = 3;
+        int maxNoOfTasks = 10;
+        int numOfTasks = 10;
+        // Create a ThreadPool with 10 threads and a capacity of 10 tasks
+        ThreadPool threadPool = new ThreadPool(noOfthreads, maxNoOfTasks);
+
+        List<Runnable> tasks = new ArrayList<>();
+        // Create some tasks
+        for (int i = 0; i < numOfTasks; i++) {
+            final int taskNumber = i;
+            Runnable task = () -> System.out.println("Task " + taskNumber + " executed by "+Thread.currentThread().getName());
+            tasks.add(task);
+        }
+
+        // Add the tasks to the ThreadPool
+        try {
+            for (Runnable task:tasks) {
+                threadPool.execute(task);
+            }
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+
+        // Wait until all tasks are finished
+        threadPool.waitUntilAllTasksFinished();
+
+        // Stop the ThreadPool
+        threadPool.stop();
+    }
+}