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This article mainly explains "what are the ways to create Java threads". The content in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought. Let's study and learn "what are the ways to create Java threads"?

1 、 Thread

Inherit the Thread class and override the run method

Class ThreadDemo1 extends Thread {@ Override public void run () {log.info ("{}", Thread.currentThread () .getName ());}}

Thread startup mode:

ThreadDemo1 T1 = new ThreadDemo1 (); t1.setName ("T1"); t1.start ()

Simple and easy to write:

Thread T1 = new Thread () {@ Override public void run () {log.info ("{}", Thread.currentThread (). GetName ());}}; t1.setName ("T1"); t1.start (); 2, Runnable and Thread

The constructor of the Thread class supports the implementation class passed into Runnable

Public Thread (Runnable target) {init (null, target, "Thread-" + nextThreadNum (), 0);} Thread (Runnable target, AccessControlContext acc) {init (null, target, "Thread-" + nextThreadNum (), 0, acc, false);}

Runnable is a functional interface FunctionalInterface

@ FunctionalInterfacepublic interface Runnable {/ / No return value public abstract void run ();}

Therefore, you need to create a class to implement the Runnable interface and override the run method.

Class ThreadDemo2 implements Runnable {@ Override public void run () {log.info ("{}", Thread.currentThread () .getName ());}}

Simple and easy to write:

Thread T2 = new Thread (()-> log.info ("{}", Thread.currentThread (). GetName ()), "T2"); t2.start (); 3, Runnable and Thread

Callable, like Runnable, is also a functional interface, and the difference between the two is very obvious. The run method in Runnable does not return a value, while the run method in Callable has a return value (you can return a value type through a generic constraint). So you can use Callable when you need to get the return value of thread execution.

@ FunctionalInterfacepublic interface Callable {/ / with return value V call () throws Exception;}

In the constructor of Thread, you don't see Callable, only Runnable

At this point, you need a class that can submit Callable to Thread, which is the FutureTask;FutureTask implementation class Runnable interface.

And FutureTask provides the constructor that is passed into Callable

Public FutureTask (Callable callable) {if (callable = = null) throw new NullPointerException (); this.callable = callable; this.state = NEW; / / ensure visibility of callable}

Therefore, you can pass in Callable via FutureTask, and then pass FutureTask to Thread.

ThreadDemo3 implements Callable {@ Override public Integer call () throws Exception {log.info ("{}", Thread.currentThread (). GetName ()); return 1998;}} / / Callable implementation class ThreadDemo3 callable = new ThreadDemo3 (); / / create FutureTaskFutureTask task = new FutureTask (callable) through Callable; / / create ThreadThread T3 = new Thread (task, "T3") through FutureTask; t3.start ()

Simple and easy to write:

Thread T3 = new Thread (new FutureTask (()-> {log.info ("{}", Thread.currentThread (). GetName ()); return 1998;}), "T3"); t3.start (); 4.

There are three ways to create a thread:

How to choose Thread, Runnable+Thread and Callable+FutureTask+Thread;?

First of all, in the actual development process, we will not create threads directly, because frequent creation and destruction of threads is expensive, and it is not conducive to management and release, so thread resources are managed by designing thread pools in the project.

Compared with Thread and Runnable+Thread, Runnable+Thread decouples thread creation from task module, makes code design more flexible, facilitates task submission, and is more convenient to use with thread pool.

Callable+FutureTask+Thread is suitable for scenarios where you need to get the results returned by the thread.

5. Attention items

Thread.start () is used many times in this article; it should be noted that the start () method of the calling thread indicates that the thread starts, but whether the thread executes is uncertain, which requires operating system scheduling, and the thread is assigned to the CPU execution time slice before it can execute. Under multi-core CPU, multiple threads start at the same time, and the threads execute alternately, and the execution sequence is uncertain.

Thank you for reading, the above is the content of "what is the way to create Java threads?" after the study of this article, I believe you have a deeper understanding of the way Java threads are created, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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