Demo of the runnable interface and stopping/restarting threads

main.java

import java.util.Scanner;

/*
   While running:
   enter 1 to print the current random number from the thread
   enter 2 to terminate the current thread, which should leave it existing
    so you can access the random number even though it wont change
   enter 3 to restart the thread (note that the runnable class was not reinstantiated)
 */

public class main {
public static void main(String[] args) {
    TestThread r = new TestThread();
    Thread thread = new Thread(r, "initial thread");
    thread.start();
    Scanner reader = new Scanner(System.in);
    int uniqueID = 0;
    while(true) {
        System.out.print("Enter a number: ");
        int n = reader.nextInt();
        if(n==2) {
            r.terminate();
        }
        else if(n==3) {
            uniqueID++;
            thread = new Thread(r, "new thread id = " + Integer.toString(uniqueID));
            thread.start();
        }
        else{
            System.out.println("Current num: " + r.getNum());
        }
    }
}
}

TestThread.java

import java.util.Random;


public class TestThread implements Runnable {
private int num;
private Random rand;
private boolean enabled;

TestThread(){
    rand = new Random();
    System.out.println("Constructing runnable in: " + Thread.currentThread().getName());
}

public void run() {
    System.out.println("Running thread: " + Thread.currentThread().getName());
    enabled = true;
    while(enabled) {
        num = rand.nextInt(50) + 1;
    }
}

public int getNum(){
    return num;
}

public void terminate(){
    enabled = false;
    System.out.println("Disabling thread");
}
}