Ordering threads to run in the order they were created/started

Question

How can i order threads in the order they were instantiated.e.g. how can i make the below program print the numbers 1...10 in order.

public class ThreadOrder         


        

Answer 1

This can be done without using synchronized keyword and with the help of volatile keyword. Following is the code.

package threadOrderingVolatile;

public class Solution {
    static volatile int counter = 0;
    static int print = 1;
    static char c = 'A';

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Thread[] ths = new Thread[4];
        for (int i = 0; i < ths.length; i++) {
            ths[i] = new Thread(new MyRunnable(i, ths.length));
            ths[i].start();
        }
    }

    static class MyRunnable implements Runnable {
        final int thID;
        final int total;

        public MyRunnable(int id, int total) {
            thID = id;
            this.total = total;
        }

        @Override
        public void run() {
            while(true) {
                if (thID == (counter%total)) {
                    System.out.println("thread " + thID + " prints " + c);
                    if(c=='Z'){
                        c='A';
                    }else{
                        c=(char)((int)c+1);
                    }
                    System.out.println("thread " + thID + " prints " + print++);
                    counter++;                  
                } else {
                    try {
                        Thread.sleep(30);
                    } catch (InterruptedException e) {
                        // log it
                    }
                }
            }
        }

    }

}

Following is the github link which has a readme, that gives detailed explanation about how it happens. https://github.com/sankar4git/volatile_thread_ordering