温故知新----线程之Runnable与Callable接口的本质区别
预备知识：Java中的线程对象是Thread,新建线程也只有通过创建Thread对象的实例来创建。
先说结论
1 Runnable没有返回值的FunctionalInterface(jdk 1.8概念)接口，相反Callable是有返回值的FunctionalInterface接口
2 Runnable + Thread 创建一个无返回结果的任务线程
3 Runnable + Callable +Thread 创建一个有返回结果的任务线程
一：Runnable 示例
创建一个无返回结果的任务线程，so eazy !!!!
public static void main(String[] args) { new Thread(new Runnable() { @Override public void run() { System.out.println(Thread.currentThread().getName() + "我是一个无返回结果的任务线程"); } },"线程一:").start(); //start()开启任务 } 二：Callable示例
2.1 JAVA异步编程之Callbacks与Futures模型 我是用Executors线程池的方式来创建的。
2.2 用最原始的方法
public class PrimitiveCallable implements Callable, Runnable { public static void main(String[] args) { //实现 new Thread(new PrimitiveCallable(), "线程二:").start(); } @Override public void run() {//Runnable实现 try { Object call = this.call(); System.out.println(call); } catch (Exception exception) { exception.printStackTrace(); } } @Override public Object call() throws Exception { //Callable 实现 return "异步任务返回的结果!!!"; } } 2.3 FutureTask 一种jdk的实现方式
public class FutureTask<V> implements RunnableFuture<V> { //RunnableFuture 实现了以上2个接口 ........省略......... public void run() { //重写run实现 if (state != NEW || !UNSAFE.compareAndSwapObject(this, runnerOffset, null, Thread.currentThread())) return; try { Callable<V> c = callable; //构建对象是传入的参数 if (c != null && state == NEW) { V result; boolean ran; try { result = c.call(); //调用任务并返回结果 ran = true; } catch (Throwable ex) { result = null; ran = false; setException(ex); //设置异常时的结果 } if (ran) set(result); //设置结果 } } finally { runner = null; int s = state; if (s >= INTERRUPTING) handlePossibleCancellationInterrupt(s); } } ........省略......... } 小结
1 不要纠结有几种创建线程的方法了，就一种即通过Thread，但Thread有9个构造函数方法
2 9个构造函数方法
1 public Thread() 2 public Thread(Runnable target) 3 Thread(Runnable target, AccessControlContext acc) 4 public Thread(ThreadGroup group, Runnable target) 5 public Thread(String name) 6 public Thread(ThreadGroup group, String name) 7 public Thread(Runnable target, String name) 8 public Thread(ThreadGroup group, Runnable target, String name) 9 public Thread(ThreadGroup group, Runnable target, String name, long stackSize) 
