Java Multi Thread problem.

Question

Hi guys . . . i need so much help. i am trying to implement matrix multiplication using threads.
For some reason when iam multiplying the matrices i have the threads waiting too long.. they wait wait wait.. then do the job and then wait wait wait.
Here is the code for my thread pool class
package concurentNaive;
import java.util.*;
public class ThreadPool {
     protected Thread threads[] = null;     
     protected EndPool endPool = new EndPool();
     Collection jobs = new ArrayList(5);
     public PriorityQueue<MatrixJob> pq = new PriorityQueue<MatrixJob>();
     public ThreadPool(int size,PriorityQueue qu){
          this.pq = qu;
          threads = new worker[size];
          for (int i=0;i<threads.length;i++){
               threads[i] = new worker(this);
               threads.start();
     public synchronized void assign(Runnable r){
          endPool.workerBegin();
          jobs.add(r);
          System.out.println(Thread.currentThread());
          notify();
     * Get a new work
     * @return
     public synchronized Runnable getAssignement(){
          try {
               while ( !jobs.iterator().hasNext() )
                    wait(1);
                    System.out.print(Thread.currentThread());
               Runnable r = (Runnable)jobs.iterator().next();
               jobs.remove(r);
               return r;
               } catch (Exception e) {
                    endPool.workerEnd();
               return null;
     public void complete(){
          endPool.waitBegin();
          endPool.waitDone();
     protected void finalize(){
          endPool.reset();
          for (int i=0;i<threads.length;i++){
               threads[i].interrupt();
               endPool.workerBegin();
               threads[i].destroy();
     * Class for the pool component threads.The thread scans and executes tasks.
     * @author Krack
     class worker extends Thread{
          public boolean busy;
          public ThreadPool owner;
          worker(ThreadPool o){
               this.owner = o;
          public void run(){
               Runnable target = null;
               do {
                    target = owner.getAssignement();
                    if (target!=null) {
                    target.run();
                    owner.endPool.workerEnd();
                    } while (target!=null);
and here is my thread :
ublic class TheWorker implements Runnable{
          private int[] answer;
          private MatrixJob myJob;
          private long time1;
          public TheWorker(MatrixJob job){
           this.myJob = job;
           time1 = System.currentTimeMillis();
           public void run()
                //MatrixJob theJob = this.myJob;
                answer = new int[myJob.row.length];
                for (int i=0;i<myJob.row.length;++i){
                     for (int j=0;j<myJob.cols.length;++j){
                          answer=0;
                         for (int k=0;k<myJob.cols[j].length;k++){
                              answer[i] += myJob.row[i]*myJob.cols[j][k];
                    for(int i=0;i<answer.length;i++){
                         System.out.print(answer[i]+" ");
                    }     System.out.println();
          public int[] getAnswer() {
               return answer;
Any help is much appreciated. Thank you much.

Answer 1

How do you know that they are waiting?