Re: thread wait

 korcs <>
Mon, 13 Aug 2007 04:57:53 -0700
On 12 Aug., 23:57, Patricia Shanahan <> wrote:

korcs wrote:

Hi All,

I have a problem with suspending a thread.

As suspend() has deprecated I am trying to use the wait() - notify()
combination, but after the thread pauses it won't resume again.


Does anyone have a clue why the code is not working?

I can't work out what is going on, but one obvious problem is that it
looks as though some actions on threadsSuspended appear to be outside
the synchronized blocks.

Given the lack of a complete program, it is hard to check issues such as
whether the event handling thread gets suspended and whether the same
object is used for all synchronization that protects the same variable.

Any chance of an SSCCE? See


Hi Patricia,

Here is an SSCCE:

import java.awt.*;
import java.awt.event.*;
import java.util.Vector;

public class DynamicPathGenerator extends Frame implements Runnable {

     * Member variables
     * @param clock Thread that provides the ticks for the main program
     * @param clock_period Shows how often the clock ticks
     * @param serialVersionUID Id needed for serialization
     * @param ta TextArea for system outputs
    Thread clock;
    boolean threadsSuspended = false;
    static final int clock_period = 1000;
    private static final long serialVersionUID = 1L;
    TextArea ta = new TextArea("DynamicPathGenerator ver 1.0\n\n", 10,
    int counter;

     * AWT classes

     * Window closing class
    class MyWindowCloser extends WindowAdapter {

          public void windowClosing(WindowEvent e) {


          } // method windowClosing

    } // class MyWindowCloser

     * Start button listener
    class startListener implements ActionListener {

        public void actionPerformed (ActionEvent e) {

            ta.append("DynamicPathGenerator> simulation started\n");
            threadsSuspended = false;

            if(!clock.isAlive()) {


            else {

                synchronized(this) {


        } // method actionPerformed

    } // class startListener

     * Stop button listener
    class stopListener implements ActionListener {

        public void actionPerformed (ActionEvent e) {

            ta.append("DynamicPathGenerator> simulation stopped\n");

            threadsSuspended = true;

        } // method actionPerformed

    } // class stopListener

     * Constructor of the class.
    public DynamicPathGenerator() { // CONSTRUCTOR

        clock = new Thread(this);

        Button start = new Button("Simulation starten"); //Gombok
        Button stop = new Button("Simulation beenden");

        Panel p1 = new Panel(new GridLayout(2,3));
        Panel p3 = new Panel();

        // add panel elements


        // arrange panel elements

        add(p1, BorderLayout.NORTH); add(p3, BorderLayout.SOUTH);

        // adding listeners

        start.addActionListener(new startListener () );
        stop.addActionListener(new stopListener () );

        addWindowListener( new MyWindowCloser () );


    public void putText(String text) {

    public void run()
        try {


                this.putText(new Integer(counter).toString());
                synchronized(this) {
                    while (threadsSuspended)

        } // while

        } catch (InterruptedException e) {



    } // method run

     * The main method
    public static void main(String argv[]) throws Exception {

        DynamicPathGenerator dpg = new DynamicPathGenerator();

      } // method main

} // class DynamicPathGenerator

I am really quite newby with programming threads, so I think I still
have some basic problems of understanding the concepts of thread

I read the official sun docs on the issue and I used the codes
there... So thanks if someone can point out the bug in the code above.



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