[09 Feb 2020] Print sequence using 3 threads in java

Problem

You are given 3 threads. You need to print sequence using these 3 threads.You need to print in natural order up to MAX.

For example:
Let’s say you have 3 threads. T1,T2 and T3.
If MAX is 10, you need to print:

T1 1
T2 2
T3 3
T1 4
T2 5
T3 6
T1 7
T2 8
T3 9
T1 10

We will use concept of remainder here.

• If number%3==1 then T1 will print the number and increment it else will go in the wait state.
• If number%3==2 then T2 will print the number and increment it else will go in the wait state.
• If number%3==0 then T3 will print the number and increment it else will go in the wait state.

Let me provide simple program for it.
Let’s create a class named “PrintSequenceRunnable” which will implement the Runnable interface.

public class PrintSequenceRunnable implements Runnable{
public int PRINT_NUMBERS_UPTO=10;
static int  number=1;
int remainder;
static Object lock=new Object();
PrintSequenceRunnable(int remainder)
{
this.remainder=remainder;
}
@Override
public void run() {
while (number < PRINT_NUMBERS_UPTO-1) {
synchronized (lock) {
while (number % 3 != remainder) { // wait for numbers other than remainder
try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println(Thread.currentThread().getName() + " " + number);
number++;
lock.notifyAll();
}
}
}
}

Let’s create a class named “PrintThreadsSequentiallyMain” which will implement the Runnable interface.
public class PrintThreadsSequentiallyMain {

public static void main(String[] args) {

PrintSequenceRunnable runnable1=new PrintSequenceRunnable(1);
PrintSequenceRunnable runnable2=new PrintSequenceRunnable(2);
PrintSequenceRunnable runnable3=new PrintSequenceRunnable(0);

Thread t1=new Thread(runnable1,"T1");
Thread t2=new Thread(runnable2,"T2");
Thread t3=new Thread(runnable3,"T3");

t1.start();
t2.start();
t3.start();
}
}

When you run above program, you will get below output.

T1 1
T2 2
T3 3
T1 4
T2 5
T3 6
T1 7
T2 8
T3 9
T1 10

https://java2blog.com/java-interview-programs/