Java中创建线程的几种方式

盘点一下Java中创建线程的几种方式

一、继承Thread类，重写run()方法

public class MyThread extends Thread {

    @Override
    public void run() {
        System.out.println("my thread start " + Thread.currentThread().getName());
    }

    public static void main(String[] args) {
        System.out.println("main thread start "+Thread.currentThread().getName());
        MyThread myThread = new MyThread();
        myThread.start();
    }
}

二、实现Runnable接口，并重写run()方法

public class MyThreadRunnable implements Runnable {

    @Override
    public void run() {
        System.out.println("my thread start " + Thread.currentThread().getName());
    }

    public static void main(String[] args) {
        System.out.println("main thread start " + Thread.currentThread().getName());
        MyThreadRunnable myThreadRunnable = new MyThreadRunnable();
        Thread thread = new Thread(myThreadRunnable);
        thread.start();
    }
}

三、实现Callable接口，并重写call()方法

public class MyThreadCallable implements Callable<Integer> {
    @Override
    public Integer call() throws Exception {
        System.out.println("my thread start " + Thread.currentThread().getName());
        Integer ret = 0;
        for (int i = 0; i < 10; i++) {
            ret += i;
        }
        return ret;
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        MyThreadCallable myThreadCallable = new MyThreadCallable();
        FutureTask<Integer> futureTask = new FutureTask<>(myThreadCallable);
        Thread thread = new Thread(futureTask, "A");
        thread.start();
        int ret = futureTask.get();
        System.out.println("main thread ret = " + ret + " " + Thread.currentThread().getName());
    }
}

综上，类图关系如下：

四、CompletableFuture

public class CompletableFutureDemo {
    private static ExecutorService threadPool = new ThreadPoolExecutor(
            2,
            5,
            1L,
            TimeUnit.SECONDS,
            new LinkedBlockingDeque<>(3),
            Executors.defaultThreadFactory(),
            new ThreadPoolExecutor.CallerRunsPolicy()
    );

    public static void main(String[] args) {
        CompletableFuture future1 = CompletableFuture.runAsync(() -> {
            System.out.println("执行没有返回值的任务");
        });
        CompletableFuture<String> future2 = CompletableFuture.supplyAsync(() -> {
            System.out.println("执行有返回值的任务");
            return "abc";
        });
        CompletableFuture<String> future3 = CompletableFuture.supplyAsync(() -> {
            System.out.println("线程池执行有返回值的任务");
            return "123";
        }, threadPool);
        future1.join();
        System.out.println(future2.join());
        System.out.println(future3);
        threadPool.shutdown();
    }
}