Difference between Thread vs Runnable interface in Java

 In Java, both the Thread class and the Runnable interface are used for creating and managing concurrent threads of execution. They serve similar purposes but differ in their implementation approach. Here are the key differences between the two:

Inheritance vs Interface: The Thread class is a concrete class that extends the java.lang.Thread class, making it capable of directly creating and managing threads. On the other hand, the Runnable interface is implemented by a class, and the class can be used to create a Thread object using the Runnable instance.

Extending vs Implementing: To create a thread using the Thread class, you need to extend it and override its run() method. This allows you to define the code that will be executed in the thread. In contrast, to use the Runnable interface, you need to implement the run() method in a separate class. The run() method contains the code that will be executed when the thread is started.

Reusability: The use of Runnable interface provides better reusability than extending the Thread class. With Runnable, you can implement the interface in multiple classes and create threads from different instances of those classes. This promotes a more flexible and modular design by separating the task logic from the thread management.

Single Inheritance Constraint: Java allows a class to extend only one class, which means if you extend the Thread class, you cannot extend any other class. However, by implementing the Runnable interface, you can still extend another class and implement Runnable, as Java supports multiple interfaces.

Encapsulation: Implementing Runnable separates the task (defined in the run() method) from the thread's behavior, allowing better encapsulation. It enables you to pass the Runnable instance to different thread constructors, promoting code reuse and modularity.

Resource Sharing: When multiple threads need to share resources or data, implementing Runnable is generally preferred. By passing the same instance of the Runnable implementation to multiple threads, they can access and manipulate shared resources easily. In contrast, extending the Thread class may lead to limitations in resource sharing.

In summary, the Thread class provides a convenient way to create and manage threads, while the Runnable interface offers a more flexible and reusable approach to defining thread behavior. The choice between the two depends on the specific requirements of your application and the design principles you want to follow.