Working with threads

Question

hello all.
I find some program that will help me in my work.
but know i don't know how to change it that it will fit my project. i just want to work with thread pool. i find some code that can do this.
mu problem is that i don't know how to change the task and the run functions in that program because they are interface. and when i do change them I get all the code errors.
can you give me an example how can i change this code to do some, like that the task will print something or do something else.
the code is:
thanks alot!
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package work2;
import java.util.ArrayList;
import java.util.List;
* @author vitaly87
public class ThreadPool {
/** Simple thread pool. A task is executed by obtaining a thread from
* the pool
  /** The thread pool contains instances of {@link ThreadPool.Task}.
  public interface Task {
    /** Performs the task.
     * @throws Throwable The task failed, and the worker thread won't be used again.
    void run() throws Throwable{}
    /** A task, which may be interrupted, if the pool is shutting down.
    public interface InterruptableTask extends Task {
        /** Interrupts the task.
         * @throws Throwable Shutting down the task failed.
        void shutdown() throws Throwable;
    private class Poolable {
        private boolean shuttingDown;
        private Task task;
        private Thread thread;
        Poolable(ThreadGroup pGroup, int pNum) {
            thread = new Thread(pGroup, pGroup.getName() + "-" + pNum){
                public void run() {
                    while (!isShuttingDown()) {
                        final Task t = getTask();
                        if (t == null) {
                            try {
                                synchronized (this) {
                                    if (!isShuttingDown()  &&  getTask() == null) {
                                        wait();
                            } catch (InterruptedException e) {
                                // Do nothing
                        } else {
                            try {
                                t.run();
                                resetTask();
                                repool(Poolable.this);
                            } catch (Throwable e) {
                                discard(Poolable.this);
                                resetTask();
            thread.start();
        synchronized void shutdown() {
            shuttingDown = true;
            final Task t = getTask();
            if (t != null  &&  t instanceof InterruptableTask) {
                try {
                    ((InterruptableTask) t).shutdown();
                } catch (Throwable th) {
                    // Ignore me
            task = null;
            synchronized (thread) {
                thread.notify();
        private synchronized boolean isShuttingDown() { return shuttingDown; }
        String getName() { return thread.getName(); }
        private synchronized Task getTask() {
            return task;
        private synchronized void resetTask() {
            task = null;
        synchronized void start(Task pTask) {
            task = pTask;
            synchronized (thread) {
                thread.notify();
  private final ThreadGroup threadGroup;
  private final int maxSize;
  private final List waitingThreads = new ArrayList();
  private final List runningThreads = new ArrayList();
  private final List waitingTasks = new ArrayList();
  private int num;
  /** Creates a new instance.
   * @param pMaxSize Maximum number of concurrent threads.
   * @param pName Thread group name.
  public ThreadPool(int pMaxSize, String pName) {
    maxSize = pMaxSize;
    threadGroup = new ThreadGroup(pName);
  synchronized void discard(Poolable pPoolable) {
    pPoolable.shutdown();
        runningThreads.remove(pPoolable);
        waitingThreads.remove(pPoolable);
  synchronized void repool(Poolable pPoolable) {
        if (runningThreads.remove(pPoolable)) {
            if (maxSize != 0  &&  runningThreads.size() + waitingThreads.size() >= maxSize) {
                discard(pPoolable);
            } else {
                waitingThreads.add(pPoolable);
                if (waitingTasks.size() > 0) {
                    Task task = (Task) waitingTasks.remove(waitingTasks.size() - 1);
                    startTask(task);
        } else {
            discard(pPoolable);
  /** Starts a task immediately.
   * @param pTask The task being started.
   * @return True, if the task could be started immediately. False, if
   * the maxmimum number of concurrent tasks was exceeded. If so, you
   * might consider to use the {@link #addTask(ThreadPool.Task)} method instead.
  public synchronized boolean startTask(Task pTask) {
    if (maxSize != 0  &&  runningThreads.size() >= maxSize) {
      return false;
        Poolable poolable;
    if (waitingThreads.size() > 0) {
        poolable = (Poolable) waitingThreads.remove(waitingThreads.size()-1);
    } else {
            poolable = new Poolable(threadGroup, num++);
    runningThreads.add(poolable);
        poolable.start(pTask);
    return true;
  /** Adds a task for immediate or deferred execution.
   * @param pTask The task being added.
   * @return True, if the task was started immediately. False, if
   * the task will be executed later.
  public synchronized boolean addTask(Task pTask) {
    if (startTask(pTask)) {
      return true;
    waitingTasks.add(pTask);
    return false;
  /** Closes the pool.
  public synchronized void shutdown() {
        while (!waitingThreads.isEmpty()) {
            Poolable poolable = (Poolable) waitingThreads.remove(waitingThreads.size()-1);
            poolable.shutdown();
        while (!runningThreads.isEmpty()) {
            Poolable poolable = (Poolable) runningThreads.remove(runningThreads.size()-1);
            poolable.shutdown();
  /** Returns the maximum number of concurrent threads.
   * @return Maximum number of threads.
  public int getMaxThreads() { return maxSize; }
  /** Returns the number of threads, which have actually been created,
     * as opposed to the number of currently running threads.
    public synchronized int getNumThreads() { return num; }
}

Answer 1

Sounds like you should read up on the [java tutorials |http://java.sun.com/docs/books/tutorial/essential/concurrency/] on threading.
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