Thread Pool Test
/*
DEVELOPING GAME IN JAVA
Caracteristiques
Editeur : NEW RIDERS
Auteur : BRACKEEN
Parution : 09 2003
Pages : 972
Isbn : 1-59273-005-1
Reliure : Paperback
Disponibilite : Disponible a la librairie
*/
import java.util.LinkedList;
public class ThreadPoolTest {
public static void main(String[] args) {
if (args.length != 2) {
System.out.println("Tests the ThreadPool task.");
System.out
.println("Usage: java ThreadPoolTest numTasks numThreads");
System.out.println(" numTasks - integer: number of task to run.");
System.out.println(" numThreads - integer: number of threads "
+ "in the thread pool.");
return;
}
int numTasks = Integer.parseInt(args[0]);
int numThreads = Integer.parseInt(args[1]);
// create the thread pool
ThreadPool threadPool = new ThreadPool(numThreads);
// run example tasks
for (int i = 0; i < numTasks; i++) {
threadPool.runTask(createTask(i));
}
// close the pool and wait for all tasks to finish.
threadPool.join();
}
/**
* Creates a simple Runnable that prints an ID, waits 500 milliseconds, then
* prints the ID again.
*/
private static Runnable createTask(final int taskID) {
return new Runnable() {
public void run() {
System.out.println("Task " + taskID + ": start");
// simulate a long-running task
try {
Thread.sleep(500);
} catch (InterruptedException ex) {
}
System.out.println("Task " + taskID + ": end");
}
};
}
}
/**
* A thread pool is a group of a limited number of threads that are used to
* execute tasks.
*/
class ThreadPool extends ThreadGroup {
private boolean isAlive;
private LinkedList taskQueue;
private int threadID;
private static int threadPoolID;
/**
* Creates a new ThreadPool.
*
* @param numThreads
* The number of threads in the pool.
*/
public ThreadPool(int numThreads) {
super("ThreadPool-" + (threadPoolID++));
setDaemon(true);
isAlive = true;
taskQueue = new LinkedList();
for (int i = 0; i < numThreads; i++) {
new PooledThread().start();
}
}
/**
* Requests a new task to run. This method returns immediately, and the task
* executes on the next available idle thread in this ThreadPool.
* <p>
* Tasks start execution in the order they are received.
*
* @param task
* The task to run. If null, no action is taken.
* @throws IllegalStateException
* if this ThreadPool is already closed.
*/
public synchronized void runTask(Runnable task) {
if (!isAlive) {
throw new IllegalStateException();
}
if (task != null) {
taskQueue.add(task);
notify();
}
}
protected synchronized Runnable getTask() throws InterruptedException {
while (taskQueue.size() == 0) {
if (!isAlive) {
return null;
}
wait();
}
return (Runnable) taskQueue.removeFirst();
}
/**
* Closes this ThreadPool and returns immediately. All threads are stopped,
* and any waiting tasks are not executed. Once a ThreadPool is closed, no
* more tasks can be run on this ThreadPool.
*/
public synchronized void close() {
if (isAlive) {
isAlive = false;
taskQueue.clear();
interrupt();
}
}
/**
* Closes this ThreadPool and waits for all running threads to finish. Any
* waiting tasks are executed.
*/
public void join() {
// notify all waiting threads that this ThreadPool is no
// longer alive
synchronized (this) {
isAlive = false;
notifyAll();
}
// wait for all threads to finish
Thread[] threads = new Thread[activeCount()];
int count = enumerate(threads);
for (int i = 0; i < count; i++) {
try {
threads[i].join();
} catch (InterruptedException ex) {
}
}
}
/**
* A PooledThread is a Thread in a ThreadPool group, designed to run tasks
* (Runnables).
*/
private class PooledThread extends Thread {
public PooledThread() {
super(ThreadPool.this, "PooledThread-" + (threadID++));
}
public void run() {
while (!isInterrupted()) {
// get a task to run
Runnable task = null;
try {
task = getTask();
} catch (InterruptedException ex) {
}
// if getTask() returned null or was interrupted,
// close this thread by returning.
if (task == null) {
return;
}
// run the task, and eat any exceptions it throws
try {
task.run();
} catch (Throwable t) {
uncaughtException(this, t);
}
}
}
}
}
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