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)
