Question

As in the subject do I correctly shutdown these simultaneous threads?

I assigned a volatile field and check it repeatedly in while loop.

Is there alternative way to do it(like using synchronize or wait() method), please show me.

EDIT I edited code. Is there any way of checking if Thread is alive by different method thatn isAlive();?
Perhaps:

boolean isAlive(){
    return running;
}

---

import javax.swing.JOptionPane;

public class Wat extends Thread {
    private char c;
    private int interv;
    private volatile boolean running = true;
    Object synchObj;

    public Wat(char c, int interv) {
        this.c = c;
        this.interv = interv;
        synchObj = new Object();
    }

    public void run() {
        while (running) {
            synchronized (synchObj) {
                try {
                    showChar(c);
                    synchObj.wait(interv * 100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }

    }

    public synchronized static void showChar(char c) {
        System.out.println(c);
    }

    public void shutdown() {
        running = false;
        synchronized (synchObj) {
            synchObj.notify();
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Wat w1 = new Wat('A', 3);
        Wat w2 = new Wat('B', 4);
        Wat w3 = new Wat('C', 5);
        w1.start();
        w2.start();
        w3.start();
        Object[] options = { "Shutdown A", "Shutdown B", "Shutdown C" };
        int option;
        while (w1.isAlive() || w2.isAlive() || w3.isAlive()) {
            option = JOptionPane.showOptionDialog(null,
                    "Which one would you like to shut?", "Threads",
                    JOptionPane.YES_NO_CANCEL_OPTION,
                    JOptionPane.QUESTION_MESSAGE, null, options, options[2]);
            switch (option) {
            case JOptionPane.YES_OPTION:
                w1.shutdown();
                break;
            case JOptionPane.NO_OPTION:
                w2.shutdown();
                break;
            case JOptionPane.CANCEL_OPTION:
                w3.shutdown();
                break;
            }
            Thread.sleep(1);
        }
    }
}

Answer 1

Your code will probably work fine, but the Thread.sleep is not very elegant. I would do something along these lines, calling the shutdown() method to quit the thread

 Object synchObj = new Object();

 public void run() {
    while (running) {
      synchronized (synchObj) {
         try {
            System.out.println(new Date());
            synchObj.wait(5000);
         } catch (InterruptedException e) {
             // error handling
         }
      }
    }
 }

 public void shutdown() {
    running = false;
    synchronized (synchObj) {
        synchObj.notify();
    }
 }


public static void main(String[] args) throws InterruptedException,
        IOException {
    ThreadTest test = new ThreadTest();
    test.start();
    BufferedReader tReader = new BufferedReader(new InputStreamReader(
            System.in));
    tReader.readLine();
    test.shutdown();
}

EDIT added test code