What's the Difference Between `Thread.start()` and `Runnable.run()` in Java?

Understanding the Distinction between Thread.start() and Runnable.run()

In Java concurrency, Runnable is an interface that defines a single method, run(), which contains the code that should be executed concurrently within a separate thread. The Thread class encapsulates the details of thread creation and management.

Scenario 1: Direct Execution of Runnable

In the first example:

R1 r1 = new R1();
R2 r2 = new R2();
r1.run();
r2.run();

We create instances of R1 and R2 and directly call their run() methods. This executes the code within the current thread without creating new threads. In other words, both R1 and R2 run sequentially in the main thread.

Scenario 2: Thread-Based Execution of Runnable

In the second example:

R1 r1 = new R1();
R2 r2 = new R2();
Thread t1 = new Thread(r1);
Thread t2 = new Thread(r2);
t1.start();
t2.start();

We again create instances of R1 and R2, but this time we pass them to the constructor of Thread, creating two separate thread objects. When we call t1.start() and t2.start(), two new threads are spawned, each executing the run() method of R1 and R2 respectively.

Key Differences

The crucial difference between the two examples revolves around thread creation. In the first scenario, no new threads are created, and R1 and R2 simply run within the existing main thread. In the second scenario, two separate threads are created, allowing for concurrent execution of R1 and R2.

In summary, Runnable.run() defines the code to be executed concurrently, while Thread.start() initiates a new thread to run that code. The choice of approach depends on whether you want to execute code in a new thread or the main thread.

The above is the detailed content of What's the Difference Between `Thread.start()` and `Runnable.run()` in Java?. For more information, please follow other related articles on the PHP Chinese website!