Java代码
public interface Executor {
/**
* Executes the given command at some time in the future. The command
* may execute in a new thread, in a pooled thread, or in the calling
* thread, at the discretion of the <tt>Executor</tt> implementation.
*
* @param command the runnable task
* @throws RejectedExecutionException if this task cannot be
* accepted for execution.
* @throws NullPointerException if command is null
*/
void execute(Runnable command);
}
Java代码
//接口ExecutorService继承自Executor，它的目的是为我们管理Thread对象，从而简化并发编程
public interface ExecutorService extends Executor {
<T> Future<T> submit(Callable<T> task);
<T> Future<T> submit(Runnable task, T result);
Future<?> submit(Runnable task);...
}
Java代码
public interface Callable<V> {
/**
* Computes a result, or throws an exception if unable to do so.
*
* @return computed result
* @throws Exception if unable to compute a result
*/
V call() throws Exception;
}
public interface Runnable {
public abstract void run();
}
Java代码
public interface Future<V> {
boolean cancel(boolean mayInterruptIfRunning);
/**
* Waits if necessary for the computation to complete, and then
* retrieves its result.
*
* @return the computed result
*/
V get() throws InterruptedException, ExecutionException;
V get(long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException;
}
Callable接口和Runnable接口相似，区别就是Callable需要实现call方法，而Runnable需要实现run方法；并且，call方法还可以返回任何对象，无论是什么对象，JVM都会当作Object来处理。但是如果使用了泛型，我们就不用每次都对Object进行转换了。
Runnable和Callable都是接口
不同之处：
1.Callable可以返回一个类型V，而Runnable不可以
2.Callable能够抛出checked exception,而Runnable不可以。
3.Runnable是自从java1.1就有了，而Callable是1.5之后才加上去的
4.Callable和Runnable都可以应用于executors。而Thread类只支持Runnable.
上面只是简单的不同，其实这两个接口在用起来差别还是很大的。Callable与executors联合在一起，在任务完成时可立刻获得一个更新了的Future。而Runable却要自己处理
Future接口，一般都是取回Callable执行的状态用的。其中的主要方法：
- cancel，取消Callable的执行，当Callable还没有完成时
- get，获得Callable的返回值
- isCanceled，判断是否取消了
- isDone，判断是否完成
用Executor来构建线程池，应该要做的事：
1).调用Executors类中的静态方法newCachedThreadPool(必要时创建新线程，空闲线程会被保留60秒)或newFixedThreadPool(包含固定数量的线程池)等，返回的是一个实现了ExecutorService 接口的ThreadPoolExecutor类或者是一个实现了ScheduledExecutorServiece接口的类对象。
2).调用submit提交Runnable或Callable对象。
3).如果想要取消一个任务，或如果提交Callable对象，那就要保存好返回的Future对象。
4).当不再提交任何任务时，调用shutdown方法。
举2个例子如下：
java代码
package thread.test04;
import java.util.concurrent.*;
public class ThreadTestA {
public static void main(String[] args) {
ExecutorService e=Executors.newFixedThreadPool(10);
e.execute(new MyRunnableA());
e.execute(new MyRunnableB());
e.shutdown();
}
}
class MyRunnableA implements Runnable{
public void run(){
System.out.println("Runnable:run()....");
int i=0;
while(i<20){
i++;
for(int j=0;j<1000000;j++);
System.out.println("i="+i);
}
}
}
class MyRunnableB implements Runnable{
public void run(){
char c='A'-1;
while(c<'Z'){
c++;
for(int j=0;j<1000000;j++);
System.out.println("c="+c);
}
}
}
java代码
package thread.test04;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
public class ThreadTestB {
public static void main(String[] args) {
ExecutorService e=Executors.newFixedThreadPool(10);
Future f1=e.submit(new MyCallableA());
Future f2=e.submit(new MyCallableA());
Future f3=e.submit(new MyCallableA());
Future f4=e.submit(new MyCallableA());
Future f5=e.submit(new MyCallableA());
System.out.println("--Future.get()....");
try {
System.out.println(f1.get());
System.out.println(f2.get());
System.out.println(f3.get());
System.out.println(f4.get());
System.out.println(f5.get());
} catch (InterruptedException e1) {
e1.printStackTrace();
} catch (ExecutionException e1) {
e1.printStackTrace();
}
e.shutdown();
}
}
class MyCallableA implements Callable<String>{
public String call() throws Exception {
System.out.println("开始执行Callable");
String[] ss={"zhangsan","lisi"};
long[] num=new long[2];
for(int i=0;i<1000000;i++){
num[(int)(Math.random()*2)]++;
}
if(num[0]>num[1]){
return ss[0];
}else if(num[0]<num[1]){
throw new Exception("弃权!");
}else{
return ss[1];
}
}
}