我要评论java.util.concurrent.callable对象可以返回由线程完成的计算结果，而runnable接口只能运行线程。 callable对象返回future对象，该对象提供监视线程执行的任务进度的方法。 future对象可用于检查callable的状态，然后线程完成后从callable中检索结果。 它还提供超时功能。
语法
//submit the callable using threadexecutor //and get the result as a future object future result10 = executor.submit(new factorialservice(10)); //get the result using get method of the future object //get method waits till the thread execution and then return the result of the execution. long factorial10 = result10.get();
实例
以下testthread程序显示了基于线程的环境中futures和callables的使用。
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 testthread {
public static void main(final string[] arguments) throws interruptedexception, executionexception {
executorservice executor = executors.newsinglethreadexecutor();
system.out.println("factorial service called for 10!");
future<long> result10 = executor.submit(new factorialservice(10));
system.out.println("factorial service called for 20!");
future<long> result20 = executor.submit(new factorialservice(20));
long factorial10 = result10.get();
system.out.println("10! = " + factorial10);
long factorial20 = result20.get();
system.out.println("20! = " + factorial20);
executor.shutdown();
}
static class factorialservice implements callable<long>{
private int number;
public factorialservice(int number) {
this.number = number;
}
@override
public long call() throws exception {
return factorial();
}
private long factorial() throws interruptedexception{
long result = 1;
while (number != 0) {
result = number * result;
number--;
thread.sleep(100);
}
return result;
}
}
}这将产生以下结果。
factorial service called for 10!
factorial service called for 20!
10! = 3628800
20! = 2432902008176640000
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