java获取多线程的4种方法

java启动多线程的4种方法

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继承Thread类

public class ThreadTest1 extends Thread {    @Override    public void run() {        for (int i = 0; i < 5; i++) {            System.out.println("Thread is printing");            try {                sleep(1000);            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }    public static void main(String[] args) {        ThreadTest1 myThread = new ThreadTest1();        myThread.start();        for (int i = 0; i < 3; i++) {            System.out.println("Main is printing");            try {                sleep(1000);            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }}

运行结果：

Main is printingThread is printingMain is printingThread is printingThread is printingMain is printingThread is printingThread is printing

实现Runnable接口

public class ThreadTest2 implements Runnable {    @Override    public void run() {        for (int i = 0; i < 5; i++) {            System.out.println("Thread is printing");            try {                Thread.currentThread().sleep(1000);            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }    public static void main(String[] args) {        ThreadTest2 myThread = new ThreadTest2();        Thread thread = new Thread(myThread);        thread.start();        for (int i = 0; i < 3; i++) {            System.out.println("Main is printing");            try {                Thread.currentThread().sleep(1000);            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }}

运行结果

Main is printingThread is printingMain is printingThread is printingMain is printingThread is printingThread is printingThread is printing

实现Callable接口

这种方法可以返回线程执行的结果。

import java.util.concurrent.Callable;import java.util.concurrent.ExecutionException;import java.util.concurrent.FutureTask;public class ThreadTest3 implements Callable<String> {    @Override    public String call() throws Exception {        for (int i = 0; i < 5; i++) {            System.out.println("Thread is printing");            Thread.currentThread().sleep(1000);        }        return "Done";    }    public static void main(String[] args) {        ThreadTest3 myThread = new ThreadTest3();        FutureTask<String> futureTask = new FutureTask<String>(myThread);        Thread thread = new Thread(futureTask);        thread.start();        for (int i = 0; i < 3; i++) {            System.out.println("Main is printing");            try {                Thread.currentThread().sleep(1000);            } catch (InterruptedException e) {                e.printStackTrace();            }        }        try {            System.out.println("Thread return: " + futureTask.get());        } catch (InterruptedException e) {            e.printStackTrace();        } catch (ExecutionException e) {            e.printStackTrace();        }    }}

运行结果

Main is printingThread is printingMain is printingThread is printingMain is printingThread is printingThread is printingThread is printingThread return: Done

通过线程池获取线程

Java通过Executors提供四种线程池

• CachedThreadPool 创建可缓存的线程池
• FixedThreadPool 创建定长的线程池，超出线程池长度的线程在队列中等待
• ScheduledThreadPool 创建一个定长的线程池，支持定时和周期性任务
• SingleThreadExecutor 创建一个单线程的线程池，所有任务通过指定顺序（FIFO,LIFO,优先级）执行

这里就不详细介绍四种线程池的区别了。

import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;public class ThreadTest4 {    public static void main(String[] args) {        ExecutorService cachedThreadPool = Executors.newCachedThreadPool();        for (int i = 0; i < 5; i++) {            final int j = i;            cachedThreadPool.execute(new Runnable() {                @Override                public void run() {                    for (int k = 0; k < 2; k++) {                        System.out.printf("Thread %d is printing\n", j);                        try {                            Thread.currentThread().sleep(1000 );                        } catch (InterruptedException e) {                            e.printStackTrace();                        }                    }                }            });        }    }}

运行结果：

Thread 0 is printingThread 4 is printingThread 3 is printingThread 2 is printingThread 1 is printingThread 1 is printingThread 2 is printingThread 3 is printingThread 4 is printingThread 0 is printing