Java使用Runnable和Callable实现多线程的区别详解

public class ThreadDemo{
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
             //创建并启动由实现Runnable接口创建的线程
            new Thread(new Runner(),"Thread"+i).start();
        }
    }
}

//实现Runnable接口
class Runner implements Runnable{
    //实现run方法
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+"有实现Runnable接口创建");
    }
}

public class ThreadDemo{
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        for (int i = 1; i <= 5; i++) {
            //使用FutureTask保存线程结果
            FutureTask<String> futureTask = new FutureTask<String>(new Caller());
            //创建并启动由实现Callable创建的线程
            new Thread(futureTask,"Thread"+i).start();
            //获取线程执行结果
            System.out.println(futureTask.get());
        }
    }
}

//实现Callable接口
class Caller implements Callable{
    //实现Call接口
    @Override
    public Object call() throws Exception {
        String result = Thread.currentThread().getName()+"由实现Callable接口创建";
        return result;
    }
}

//FutureTask实现了RunnableFuture接口
public class FutureTask<V> implements RunnableFuture<V> {}

//再看RunnableFuture接口，继承了Runnable接口
public interface RunnableFuture<V> extends Runnable, Future<V> {
    void run();
}

//回到FutureTask,找到run方法
public void run() {
    ...
    Callable<V> c = callable;
    if (c != null && state == NEW) {
        V result;
        boolean ran;
        try {
            //获取call的返回值
            result = c.call();
            ran = true;
        } catch (Throwable ex) {
            result = null;
            ran = false;
            setException(ex);
        }
        if (ran)
            set(result);
    }
    ...
}

//看一下set方法
protected void set(V v) {
    if (UNSAFE.compareAndSwapInt(this, stateOffset, NEW, COMPLETING)) {
        outcome = v;
        ...
    }
}

//再看一下FutureTask的构造函数
public FutureTask(Callable<V> callable) {
        if (callable == null)
            throw new NullPointerException();
        this.callable = callable;
        this.state = NEW;
}