性能明智，可以更快地实现Runnable或扩展Thread类

Question

We can create a thread using Implementing Runnable or by extending a thread class. Can anyone tell me performance wise which is faster implementing a Runnable or extending a Thread class and Why? Also I know while implementing Runnable we can implement more Interfaces and also extend a class. Extending a class is something we lose out if we directly extend a Thread class. But is there any performance difference in both scenarios

Answer 1

Performance-wise there is no difference between the two. Yet using "implements Runnable" is preferable because it gives you more freedom(extending another class,...) and the same object is shared across multiple threads(which also reduces the used memory).

Answer 2

It depends (as always):

• If you would run it only once, the Thread extension has no drawback except it is not as flexible and harder to test (eg in a unit test).
• If you want to run it more often, the Runnable is more flexible as you can pass it to an Executor using a thread pool. By doing so you would get a better performance as the overhead of thread creation for each execution will be dropped.

If you implement a Runnable you have various ways to execute the code (synchronous in a unit test, using an executor, or even wrap it with a Thread anyway). And the pure thread extension never has a better performance, it can be equal only. Implementing Runnable only is always the better option also by allowing multiple interfaces or using an independent inheritance, it is simply the better design. Following this I would never extend Thread .