4.1 与Runnable区别

1. 方法不同，一个是run，一个是call
2. call有返回值，run没有
3. call抛异常，run没有

4.2 Callable的使用

1. Runnable->RunnableFuture->FutureTask(实现类)
2. FutureTask有构造方法：public FutureTask(Callable<V> callable)
3. 示例

   public class CallableDemo {
       public static void main(String[] args) throws ExecutionException, InterruptedException {
           FutureTask futureTask = new FutureTask(new MyThread());
           new Thread(futureTask,"A").start();
           System.out.println(futureTask.get());
   //        new Thread(new FutureTask<Integer>(new MyThread())).start();
       }
   }
   
   class MyThread implements Callable<Integer>{
   
       @Override
       public Integer call() throws Exception {
           System.out.println("******************");
           return 1024;
       }
   }

4. get()方法的使用

   public class CallableDemo {
       public static void main(String[] args) throws ExecutionException, InterruptedException {
           FutureTask futureTask = new FutureTask(new MyThread());
           new Thread(futureTask,"A").start();
           System.out.println(Thread.currentThread().getName()+"线程完成");
           System.out.println(futureTask.get());
   //        new Thread(new FutureTask<Integer>(new MyThread())).start();
       }
   }
   
   class MyThread implements Callable<Integer>{
   
       @Override
       public Integer call() throws Exception {
           System.out.println("******************");
           try {
               TimeUnit.SECONDS.sleep(4);
           } catch (InterruptedException e) {
               e.printStackTrace();
           }
           return 1024;
       }
   }

   输出结果：

   ******************
   main  main线程完成
   1024

   get方法要在后面调用，因为一旦调用，程序会一直等待到该线程完成
5. 多个分线程

   public class CallableDemo {
       public static void main(String[] args) throws ExecutionException, InterruptedException {
           FutureTask futureTask = new FutureTask(new MyThread());
           new Thread(futureTask,"A").start();
           new Thread(futureTask,"B").start();
           System.out.println(Thread.currentThread().getName()+"线程完成");
           System.out.println(futureTask.get());
   //        new Thread(new FutureTask<Integer>(new MyThread())).start();
       }
   }
   
   class MyThread implements Callable<Integer>{
   
       @Override
       public Integer call() throws Exception {
           System.out.println(Thread.currentThread().getName());
           try {
               TimeUnit.SECONDS.sleep(4);
           } catch (InterruptedException e) {
               e.printStackTrace();
           }
           return 1024;
       }
   }

   结果：

   A
   main线程完成
   1024