多线程三种方式实现

一、继承Thread

a、直接使用run运行public class MyThread extends Thread{ private String name; public MyThread(String name){ this.name = name; } @Override public void run() { for (int i = 0; i < 3; i++) { System.out.println(this.name +"-->"+ i); } }}class ThreadDemo{ public static void main(String[] args) { MyThread threadA = new MyThread("线程A"); MyThread threadB = new MyThread("线程B"); MyThread threadC = new MyThread("线程C"); threadA.run(); threadB.run(); threadC.run(); }}结果线程A-->0线程A-->1线程B-->0线程B-->1线程C-->0线程C-->1分析：此时并未启动多线程，多线程启动的唯一方法是Thread中的start()方法b、使用start()方法class ThreadDemo{ public static void main(String[] args) { MyThread threadA = new MyThread("线程A"); MyThread threadB = new MyThread("线程B"); MyThread threadC = new MyThread("线程C"); threadA.start(); threadB.start(); threadC.start(); }}结果：线程A-->0线程C-->0线程A-->1线程C-->1线程B-->0线程B-->1注：每次运行结果不一样疑问：为什么多线程启动方法不是run()而是start(),查看源码

总结：start()中包含native start0()方法。在java系统中，有一套JNI（java native interface）技术，java系统可以方便调用操作系统的资源。所以，多线程启动，唯一方法是Thread.start()

二、实现Runnable

public class MyRunnableTest implements Runnable{ private String name; public MyRunnableTest(String name){ this.name = name; } @Override public void run() { for (int i = 0; i < 3; i++) { System.out.println(Thread.currentThread().getName()+"->"+this.name +"-->"+ i); } }}class MyRunnableDemo{ public static void main(String[] args) { MyRunnableTest myRunnableTestA = new MyRunnableTest("线程A"); MyRunnableTest myRunnableTestB = new MyRunnableTest("线程B"); MyRunnableTest myRunnableTestC = new MyRunnableTest("线程C"); new Thread(myRunnableTestA).start(); new Thread(myRunnableTestB).start(); new Thread(myRunnableTestC).start(); }}结果：Thread-0->线程A-->0Thread-0->线程A-->1Thread-1->线程B-->0Thread-1->线程B-->1Thread-2->线程C-->0Thread-2->线程C-->1注：每次运行结果不一样小结：上面提到过，多线程启动时Thread.start()方法。

三、实现Callable

public class CallableTest implements Callable<String> { @Override public String call() throws Exception { System.out.println("线程" + Thread.currentThread().getName()); return Thread.currentThread().getName() + "启动"; }}class CallableDemo { public static void main(String[] args) throws ExecutionException, InterruptedException { CallableTest callableTestA = new CallableTest(); CallableTest callableTestB = new CallableTest(); CallableTest callableTestC = new CallableTest(); FutureTask<String> futureTaskA = new FutureTask<String>(callableTestA); FutureTask<String> futureTaskB = new FutureTask<String>(callableTestB); FutureTask<String> futureTaskC = new FutureTask<String>(callableTestC); new Thread(futureTaskA).start(); new Thread(futureTaskB).start(); new Thread(futureTaskC).start(); futureTaskA.get(); futureTaskB.get(); futureTaskC.get(); System.out.println("A线程返回结果" + futureTaskA.get()); System.out.println("B线程返回结果" + futureTaskB.get()); System.out.println("C线程返回结果" + futureTaskC.get()); }}结果：线程Thread-0线程Thread-2线程Thread-1A线程返回结果Thread-0启动B线程返回结果Thread-1启动C线程返回结果Thread-2启动