这一章节我们来讨论一下Callable、Future和FutureTask的用法与关系。
1.关系
（1）Callable是Runnable的封装的异步运算任务
（2）Future用来保存Callable异步运算的结果
（3）FutureTask封装Future的实体类
2.Future
我们在这里详细介绍一下Future，因为它比较复杂，首先看看他的源代码：
public interface Future<V> {
boolean cancel(boolean mayInterruptIfRunning);
boolean isCancelled();
boolean isDone();
V get() throws InterruptedException, ExecutionException;
V get(long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException;
}
它里面包含了几个方法
get：得到结果
get（timeout，unit）计算是否超时得到结果
cancle：取消任务
isDone、isCancle：判断任务状态
3.例子：
Callable和FutureTask
package com.ray.ch17;
import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;
public class Test {
public static void main(String[] args) throws InterruptedException,
ExecutionException {
Callable<Integer> callable = new MyCall();
FutureTask<Integer> futureTask = new FutureTask<Integer>(callable);
Thread thread = new Thread(futureTask);
thread.start();
Thread.sleep(100);
if (!futureTask.isDone()) {
System.out.println(futureTask.get());
}
if (!futureTask.isCancelled()) {
futureTask.cancel(true);
System.out.println("cancelled");
}
}
}
class MyCall implements Callable<Integer> {
@Override
public Integer call() throws Exception {
System.out.println("doing something...");
Thread.sleep(1000);
return new Random().nextInt(50);
}
}
我们只需要将上面main方法里面的两个if互换就可以得出不同的结果。
Callable和Future
package com.ray.ch17;
import java.util.Random;
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 Test {
public static void main(String[] args) throws InterruptedException,
ExecutionException {
ExecutorService executors = Executors.newCachedThreadPool();
Callable<Integer> callable = new MyCall();
Future<Integer> future = executors.submit(callable);
System.out.println(future.get());
}
}
class MyCall implements Callable<Integer> {
@Override
public Integer call() throws Exception {
System.out.println("doing something...");
Thread.sleep(1000);
return new Random().nextInt(50);
}
}
总结：这一章节主要介绍了Callable、Future和FutureTask的用法与关系。
这一章节就到这里，谢谢。
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