Using Thread waiting() method

[nicoeschpiko]

I am trying to send a notify to an available Thread (first Thread i can find in a pool currently in a WAITING state), but am unable to. I am trying to send the notify alert to a thread running in a separate class, although this class is included in the same package. Here is the Server.java file from which I am trying to notify my available thread:


***************Server.java***********************

package dir.test;
 
 
import java.util.ArrayList;
import java.util.LinkedList;
 
public class Server {
	static private final int THREADCOUNT=5;
 
 
	public static void main(String[] args) throws InterruptedException {
		ArrayList<Thread> objThreads = new ArrayList<Thread>(THREADCOUNT);
 
		for (int i=0; i<THREADCOUNT; i++) {
			objThreads.add(i, new Thread(new ObjThread(1)));
			objThreads.get(i).start();
		}
 
		try {
			for (int i=0; i<objThreads.size(); i++) {
				if ( (objThreads.get(i).getState())==Thread.State.WAITING ) {
					System.out.println("Thread " + i + " is in state: WAITING.");
					objThreads.get(i).notify();
					System.out.println("Thread " + i + " has been notified.");
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		} catch (Throwable t) {
			System.err.println("Caught throwable t: " + t);
		}
	}
}

**********************************************

and here's the ObjThread.java file...

***************ObjThread.java********************* **

package dir.test;
 
import java.lang.Runnable;
import java.util.*;
 
 
public class ObjThread implements Runnable {
	private int int_var;
 
	public ObjThread(int int_var) {
		this.int_var = int_var;
	}
 
	public synchronized void run() {
		while ( true ) {
			try {
				System.out.println("test...before wait");
				wait();
				System.out.println("test...after wait.  int variable value: " + int_var);
			} catch ( InterruptedException e ) { }
		}
	}
}

**********************************************


The thread never gets to the statement:
System.out.println("test...after wait. int variable value: " + int_var);

My output is:
$ java dir.test.Server
test...before wait
test...before wait
test...before wait
test...before wait
test...before wait
Thread 0 is in state: WAITING.
java.lang.IllegalMonitorStateException
at java.lang.Object.notify(Native Method)
at dir.test.Server.main(Server.java:23)


Any idea how I can wake a thread from a WAITING state with this file structure so it can resume it's work?

[copeg]

Acquire a lock on the objects...flank the wait and notify by a synchronized statement on the object you are calling prior to calling these methods.