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1.继承Thread类，重写run方法；2.实现Runnable接口，重写run方法；3.实现Callable接口，重写call方法；4.通过线程池实现多线程（实现Runnable接口+Executors创建线程池）；

前2种方法无返回值，后2种方法有返回值。

继承Thread类，重写run方法

public class TTEST extends Thread{     @Override    public void run() {        System.out.println(Thread.currentThread().getName());    }        public static void main(String[] args) {        Thread t1 = new TTEST();        Thread t2 = new TTEST();        t1.setName("线程1");        t2.setName("线程2");        t1.start();        t2.start();    }

实现Runnable接口，重写run方法

public class RunnableThread implements Runnable{     @Override    public void run() {        System.out.println(Thread.currentThread().getName());    }     public static void main(String[] args) {        System.out.println(Thread.currentThread().getName());        RunnableThread runnableThread = new RunnableThread();        Thread t1 = new Thread(runnableThread);        t1.setName("线程1");        t1.start();    }    }

实现Callable接口，重写call方法

因为FutureTask类实现了RunnaleFuture，而RunnaleFuture又实现了Runnable接口和Future接口，通过FutureTask封装继承Callable接口的类

import java.util.concurrent.Callable;import java.util.concurrent.FutureTask; public class CollableThread implements Callable<Object>{     @Override    public Object call() throws Exception {        System.out.println(Thread.currentThread().getName());        return null;    }     public static void main(String[] args) {        System.out.println(Thread.currentThread().getName());        CollableThread collableThread = new CollableThread();        FutureTask<Object> futureTask = new FutureTask<Object>(collableThread);        Thread t1 = new Thread(futureTask);        t1.setName("线程1");        t1.start();    }    }

通过线程池实现多线程（实现Runnable接口+Executors创建线程池）

import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors; public class PoolThread implements Runnable{     private static int POOL_NUM = 10;//线程池数量        @Override    public void run() {        System.out.println(Thread.currentThread().getName());    }     public static void main(String[] args) {        ExecutorService threadPool = Executors.newFixedThreadPool(5);        for (int i = 0; i < POOL_NUM; i++) {            PoolThread poolThread = new PoolThread();            threadPool.execute(poolThread);        }        threadPool.shutdown();//关闭线程池    }    }