Java中创建多线程的三种方法：

1. 继承 Thread 类

   class MyThread extends Thread{
      @Override
      public void run() {
          // TODO Auto-generated method stub
          super.run();
      }
   }
   

调用方法

public static void main(String[] args) {
    MyThread my = new MyThread();
    my.start();
}

2. 实现 Runnable 接口

   class MyRunnable implements Runnable{
       @Override
       public void run() {
       // TODO Auto-generated method stub
    
       }
   }
   

调用方法

public static void main(String[] args) {
    MyRunnable  my = new MyRunnable ();
    new Thread(my).start();
}

3. 实现 Callable<?> 接口，支持返回结果，支持泛型

   public class MyCallable implements Callable<String>{
       @Override
       public String call() throws Exception {
           String[] str = {"First", "Second", "Third", "Fourth", "Five"};
           int index = (int) (Math.random() * 5);
           return str[index];
       }
   }
   

调用该类

public static void main(String[] args) {
    //创建任务
    MyCallable mc = new MyCallable();
    //将任务交给任务管理器
    //FutureTask<?> 是一个管理类，实现了RunnableFuture<?>接口；
    //而RunnableFuture<?>接口，实现了Runnable, Future<V>两个接口
    FutureTask<String> ft = new FutureTask<>(mc);
    new Thread(ft).start();
    
    try {
        //获取线程任务的执行结果
        System.out.println(ft.get());
    } catch (InterruptedException | ExecutionException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    //判断线程任务执行是否结束
    System.out.println(ft.isDone());
}