Implement Runnable vs Extend Thread in Java

In Java, multithreading allows multiple tasks to run concurrently, improving performance and resource utilization. There are two standard ways to create a thread:

1. Extending the Thread Class

• A class directly inherits from the Thread class and overrides its run() method.
• Each instance of this class represents a separate thread of execution

Thread is running
Thread is running

2. Implementing the Runnable Interface

• A class implements the Runnable interface and provides an implementation for the run() method.
• A Runnable object is then passed to a Thread object when creating the thread.

Thread is running
Thread is running

Key Differences Between Extending Thread and Implementing Runnable

1. Multiple Inheritance: Java does not support multiple inheritance for classes. If you extend Thread, your class cannot extend any other class. Implementing Runnable allows your class to extend another class while still enabling multithreading.

2. Resource Sharing: When implementing Runnable, a single Runnable object can be shared among multiple Thread objects, promoting better resource usage and reducing memory overhead. When extending Thread, each thread instance is a distinct object.

3. Separation of Concerns: Implementing Runnable promotes a cleaner separation between the task and the thread itself. The Runnable object defines what needs to be executed, while the Thread object handles how it is executed. Extending Thread combines the task and thread in a single class.

4. Flexibility with Executor Framework: The Runnable interface is compatible with Java's Executor framework, which provides a more advanced and flexible way to manage thread pools and task execution. Extending Thread cannot be used directly with these frameworks.