Threads stopping, suspending, and resuming

Question

I'm writing a code that involves JFrame, and a thread. The thread should take the text from a text field and write it into text area. I have 4 buttons as follows:

"Start" to start the thread.
"Stop" which stops the thread.
"Pause" which pause and continues the thread.
and "Exit" which stops the thread and exits the program.

I've created the thread and implemented "run()" function in frame's constructor, here it is:

WritingThread = new Thread(new Runnable() {
    @Override
    public void run() {
        String s = WrittenText.getText();
        while(true)
        {
            for(int i = 0; i < 4; i++)
            {
                for(int j = 0; j < s.length(); j++)
                {
                    WritingArea.append("" + s.charAt(j));
                    try {
                        Thread.sleep((int)ThreadSpeedSpinner.getValue());
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }   
                }
                WritingArea.append("\n");
            }   
            WritingArea.setText("");
        }
    }
});

and these are the buttons:

JButton btnStart = new JButton("Start");
btnStart.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        if(!WritingThread.isAlive())
            WritingThread.start();
    }
});
JButton btnStop = new JButton("Stop");
btnStop.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        if(WritingThread.isAlive())
            WritingThread.stop();
    }
});
btnPause = new JButton("Pause");
btnPause.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        if(!isPaused)
        {
            if(WritingThread.isAlive())
            {
                WritingThread.suspend();
                btnPause.setText("Continue");
                isPaused = true;
            }
        }
        else
        {
            WritingThread.resume();
            btnPause.setText("Pause");
        }
    }
});
JButton btnExit = new JButton("Exit");
btnExit.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        WritingThread.stop();
        System.exit(0);
    }
});

I have two problems showing up:

When I use stop(), suspend(), or resume(), I get a warning says "The method from the type Thread is deprecated".

When I run the program, I start the thread, then stop it, then try to start it I have this exception

Exception in thread "AWT-EventQueue-0" java.lang.IllegalThreadStateException
    at java.lang.Thread.start(Unknown Source)
    at com.HomeWork.HomeWork5$6.actionPerformed(HomeWork5.java:140)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$200(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

I don't want direct answers, I want to understand why I'm getting these errors, and if there any resources I should go through. P.S. I searched for an answer a lot and didn't get anything explaining this problem. Thanks

avoid using `stop()` ans `suspend()` on threads http://docs.oracle.com/javase/7/docs/technotes/guides/concurrency/threadPrimitiveDeprecation.html — vandale, Nov 29 '13 at 15:39
You can't restart thread once it's stopped. `suspend()` is deprecated. Read basic Oracle online manual about threads: http://docs.oracle.com/javase/tutorial/essential/concurrency/ — Victor Sorokin, Nov 29 '13 at 15:40
Read the API documentation on these methods. It explains why these methods are deprecated and it also explains that you cannot restart a thread. — Jesper, Nov 29 '13 at 15:40
A thread isn't like a video that you can just start/stop at will. — Zong, Nov 29 '13 at 15:48
I [posted](http://stackoverflow.com/a/10669623/823393) on this some time ago. — OldCurmudgeon, Nov 29 '13 at 15:54
@VictorSorokin Thanks, I didn't know that. Reading the decumantation right now :) — Maher Hejazi, Nov 29 '13 at 16:00
@ZongZhengLi Thanks for editing it. btw how did you do it :D — Maher Hejazi, Nov 29 '13 at 16:03
@OldCurmudgeon it doesn't cover the whole issue, plus, it didn't mention the exception :\ — Maher Hejazi, Nov 29 '13 at 16:06
You are better off avoiding threads: http://en.wikipedia.org/wiki/Event_dispatching_thread#Swing_and_thread_safety - http://docs.oracle.com/javase/tutorial/uiswing/misc/timer.html sounds better. — zapl, Nov 29 '13 at 16:07
@zapl I have to study it first, and study why should I avoid it, then do so, thanks for the idea. :) — Maher Hejazi, Nov 29 '13 at 16:11
@MaHeRHeJaZi - *It doesn't cover ...* which is why I posted as a comment not an answer. — OldCurmudgeon, Nov 29 '13 at 16:23
@OldCurmudgeon ah, ok, sorry and thanks for your interest :D — Maher Hejazi, Nov 29 '13 at 22:52

score 4 · Accepted Answer · edited Jun 20 '20 at 09:12

Threads acquire lock on objects. And the most important part of multithreading is to safely interweave the threads, so that all the threads can use the resource (object). If not dealt with correctly, it leads to deadlock.

When you use stop(), you are killing the thread. That thread is gone forever. It may lead the objects, that stopped thread had acquired, in a inconsistent state.

suspend() is deprecated, because once the thread is suspended other threads won't get the resource, since the suspended thread holds a lock on it.

The image below describes how threads should be correctly used. Use sleep(), wait(), and notify() for interleaving the threads efficiently.

enter image description here

May i know the reference of the image ? – Sage Nov 29 '13 at 17:18 — Sage, Nov 29 '13 at 17:18

Threads stopping, suspending, and resuming

1 Answers1