Java Semaphore - Print Alternate Numbers Sequence Using Three Threads

In this example we will be implementing multiple threads to print alternate values of sequence.
So here thread1 will print 1,4,7 thread2 will print 2,5,8 thread3 will print 3,6,9.

Semaphore - Table Of Contents
Understanding Java Semaphore
Java Semaphore - Print even and odd numbers using Threads
Java Semaphore - Print numbers sequence using three Threads

• Step 1 - Thread 1 gets the permit for semaphore1 to print one sequence numbers

  
  

• Step 2 - Thread 1 releases permit for semaphore2

  
  

• Step 3 - Thread 2 gets the permit for semaphore1 to print two sequence numbers

  
  

• Step 4 - Thread 2 releases permit for semaphore3

  
  

• Step 5 - Thread 3 gets the permit for semaphore1 to print three sequence numbers

  
  

• Step 6 - Thread 3 releases permit for semaphore1

  
  

• Step 7 - Thread 1 gets the permit for semaphore1 to print one sequence numbers

  
  

package com.javastructures;

import java.util.concurrent.Semaphore;

public class SemaphoreExample {

	public static void main(String[] args) {

		Semaphore one = new Semaphore(1);
		Semaphore two = new Semaphore(0);
		Semaphore three = new Semaphore(0);
		PrintOneNumber printOneNumber = new PrintOneNumber(one, two);
		PrintTwoNumber printTwoNumber = new PrintTwoNumber(two, three);
		PrintThreeNumber printThreeNumber = new PrintThreeNumber(three, one);

		new Thread(printOneNumber, "Print one").start();
		new Thread(printTwoNumber, "Print two").start();
		new Thread(printThreeNumber, "Print three").start();
	}

}

class PrintOneNumber implements Runnable {

	Semaphore sempahoreOne;
	Semaphore sempahoreTwo;

	public PrintOneNumber(Semaphore sempahoreOne, Semaphore sempahoreTwo) {
		super();
		this.sempahoreOne = sempahoreOne;
		this.sempahoreTwo = sempahoreTwo;
	}

	@Override
	public void run() {
		for (int i = 1;; i = i + 3) {
			try {
				sempahoreOne.acquire();
				System.out.println(i);
				sempahoreTwo.release();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}

}

class PrintTwoNumber implements Runnable {

	Semaphore sempahoreTwo;
	Semaphore sempahoreThree;

	public PrintTwoNumber(Semaphore sempahoreTwo, Semaphore sempahoreThree) {
		this.sempahoreTwo = sempahoreTwo;
		this.sempahoreThree = sempahoreThree;
	}

	@Override
	public void run() {
		for (int i = 2;; i = i + 3) {
			try {
				sempahoreTwo.acquire();

				Thread.sleep(1000);
				System.out.println(i);
				sempahoreThree.release();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}

		}

	}
}
	
	class PrintThreeNumber implements Runnable {

		Semaphore sempahoreThree;
		Semaphore sempahoreOne;

		public PrintThreeNumber(Semaphore sempahoreThree, Semaphore sempahoreOne) {
			this.sempahoreThree = sempahoreThree;
			this.sempahoreOne = sempahoreOne;
		}

		@Override
		public void run() {
			for (int i = 3;; i = i + 3) {
				try {
					sempahoreThree.acquire();

					Thread.sleep(1000);
					System.out.println(i);
					sempahoreOne.release();
				} catch (InterruptedException e) {
					e.printStackTrace();
				}

			}

		}
	}

Run the program as a Java Application -