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 guess this might help. Although it is not standard but i hope it provides a simpler approach.

public class ThreadDemo
{
    public static void main (String [] args)
    {
        PrintDemo pd=new PrintDemo();     
        MyThread1 mt1 = new MyThread1 ("T1",pd);
        MyThread2 mt2 = new MyThread2 ("T2",pd);     
        mt1.start ();
        mt2.start();
    }
}
class PrintDemo {
    private boolean oddFlag=true;
    public synchronized void printOdd(int i,String tName){
        if(oddFlag==false){
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }   
        }else{
            System.out.println("\nThread "+tName+" count:"+i);
            oddFlag=false;
            notify();
        }
    }
    public synchronized void printEven(int i,String tName){
        if(oddFlag==true){
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }   
        }else{
            System.out.println("\nThread "+tName+" count:"+i);
            oddFlag=true;
            notify();
        }
    }   
}
class MyThread1 extends Thread
{
    private PrintDemo pd;
    private String name;

    MyThread1(String threadName,PrintDemo pd){
        this.name=threadName;
        this.pd=pd;
    }  
    public void run ()  
    {
       for(int i=1;i<=50;i+=2){
            pd.printOdd(i,name);
       }
    }
}
class MyThread2 extends Thread
{
    private PrintDemo pd;
    private String name;    
    MyThread2(String threadName,PrintDemo pd){
        this.name=threadName;
        this.pd=pd;
    }   
    public void run ()
    {
        for(int i=2;i<=50;i+=2){
            pd.printEven(i,name);                   
        }
    }
}