I can’t figure out how to fix the errors.
import java.util.LinkedList;
/**
A thread pool is a group of a limited number of threads that
are used to execute tasks.
*/
public 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);
}
}
}
}
}
I have some java experience but no game developing experience with java. I purchased a book and the first chapter is about threads. so I copied the sample program into my eclipse window and got the following error.
launch error
selection does not contain a main type.
please explain what is wrong with the program.
any advise is welcome.
thanks