notify() vs notifyAll() in Java – A Complete Guide with Examples

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In this article, you will learn the key differences between notify() and notifyAll(), how and when to use them, and see real-world examples demonstrating their behavior.

What is Inter-Thread Communication in Java?

When multiple threads share resources (like objects, files, or databases), they often need to communicate with each other to avoid conflicts and ensure consistency.

For example:

• One thread might be producing data, while another is consuming it.
• The producer should pause when the buffer is full.
• The consumer should pause when the buffer is empty.

Java provides the following methods (from Object class) to manage this communication:

• wait(): causes the current thread to wait until it is notified.
• notify(): wakes up one thread waiting on the object.
• notifyAll(): wakes up all threads waiting on the object.

Understanding notify() in Java

The notify() method is used to wake up a single thread that is waiting on the monitor of the current object.