Writing a program with 2 threads which prints alternatively

Question

I got asked this question recently in an interview.

Write a program with two threads (A and B), where A prints 1 , B prints 2 and so on until 50 is r

Answer 1

I have created a pretty basic Solution for it using the Reentrant Lock.

package com.multithreding.trylock;

import java.util.concurrent.locks.ReentrantLock;

public class TryLock extends Thread {

    static int intitialCount = 50;          //Value till which you want to print
    int valueToSubtract = 0;                //Value by which difference you want to print the series like 1,2,3
    static ReentrantLock alternate = new ReentrantLock();

    public TryLock(String name) {
        this.setName(name);
    }

    public void run() {
        while (intitialCount > 1) {         

            if (valueToSubtract > 0) {
                alternate.lock();
                intitialCount = intitialCount - valueToSubtract;
                valueToSubtract = 0;
                try {
                    Thread.sleep(200);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                System.out.println("value Subtracted " + intitialCount + " by the Thread" + this.getName());
                alternate.unlock();
            } else {
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                valueToSubtract++;
            }
        }

    }

}

package com.multithreding.trylock;

public class AlternatePrint {

    public static void main(String[] args) throws InterruptedException{
        //You  can add as many thread to print then in different number of series
        TryLock t1 = new TryLock("Odd One");
        TryLock t2 = new TryLock("Even Value");
        t1.start();
        t2.start();

    }

}

This solution is modular as well,

• You can add 'n' number of Threads to print the alternate series. i.e Using 3 thread at once

• You can also print the series with more than Difference of more than 1. i.e 1,3,5 etc