Printing Even and Odd Numbers with Two Threads in Java

Learn how to effectively use multithreading in Java to print even and odd numbers in an alternating manner. Discover common pitfalls and solutions for your code. --- This video is based on the question https://stackoverflow.com/q/63084467/ asked by the user 'Aman' ( https://stackoverflow.com/u/2534054/ ) and on the answer https://stackoverflow.com/a/63084866/ provided by the user 'Andrew Vershinin' ( https://stackoverflow.com/u/5802381/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Printing even and odd number using two threads Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Printing Even and Odd Numbers with Two Threads in Java In the world of multithreading in Java, one common challenge is implementing the logic that allows two threads to print even and odd numbers in an alternating sequence. This not only tests your understanding of threading concepts but also how threads can communicate effectively by using synchronization methods. Today, we'll walk through a sample problem where both odd and even numbers are printed by two threads, highlighting some issues and providing solutions. The Problem You are tasked with creating a Java program that prints even numbers and odd numbers alternately using two separate threads. You’ve already implemented the program, but it isn't behaving as expected — both threads aren’t taking turns properly, leading to unsynchronized output. You need to ensure that the even and odd numbers are printed one after the other, utilizing Java’s wait() and notify() methods. Sample Code Here's the initial version of the code you have written: [[See Video to Reveal this Text or Code Snippet]] Current Output The output is inconsistent, displaying odd and even numbers but not in the desired alternating pattern. Let's examine the crucial problem. Understanding the Solution Identifying the issue The primary issue here lies in how the current value is being checked within the threads. In both PrintOdd and PrintEven classes, the code checks the value of current once and proceeds along its logic. This leads to a situation where the threads can go into a waiting state without further opportunity to check the updated value. Key Lines of Concern In the PrintOdd class: [[See Video to Reveal this Text or Code Snippet]] In the PrintEven class: [[See Video to Reveal this Text or Code Snippet]] Recommended Changes To resolve the issue, modify the loop conditions to continuously check the value of current from CurrentValue. You should essentially eliminate the local variable current within the thread classes, and directly call currentValue.getCurrent() to ensure you are checking against the most recent updates. Here is a suggested modification: Change the lines in PrintOdd: [[See Video to Reveal this Text or Code Snippet]] Change the lines in PrintEven: [[See Video to Reveal this Text or Code Snippet]] The Final Modified Code Here's the updated core structure which should work correctly: [[See Video to Reveal this Text or Code Snippet]] Conclusion By modifying the condition in your loop statements, you ensure that the program always checks the latest state of current before proceeding. Now your odd and even threads should successfully take turns printing numbers in sequence. With a clear understanding of synchronization and communication between threads, you are now well-equipped to tackle more complex multithreading scenarios in Java. Happy coding!