怎样返回子线程里面的值

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#热议# 上班途中天气原因受伤算工伤吗？

遗央4623
2016-12-19 · TA获得超过128个赞

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package com.ronniewang;

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 GetReturnValueFromCallable {

private static final int SLEEP_MILLS = 3000;

private static final int SECOND_MILLS = 1000;

private static int sleepSeconds = SLEEP_MILLS / SECOND_MILLS;

ExecutorService executorService = Executors.newCachedThreadPool();

/**
* 在创建多线程程序的时候，我们常实现Runnable接口，Runnable没有返回值，要想获得返回值，Java5提供了一个新的接口Callable
*/
public static void main(String[] args) {

new GetReturnValueFromCallable().testCallable();
}

private void testCallable() {

/**
* Callable需要实现的是call()方法，而不是run()方法，返回值的类型有Callable的类型参数指定，
* Callable只能由ExecutorService.submit() 执行，正常结束后将返回一个future对象
*/
Future<String> future = executorService.submit(new Callable<String>() {

public String call() throws Exception {

Thread.sleep(SLEEP_MILLS);
return "I from callable";
}
});

while (true) {
/**
* 获得future对象之前可以使用isDone()方法检测future是否完成，完成后可以调用get()方法获得future的值，
* 如果直接调用get()方法，get()方法将阻塞值线程结束
*/
if (future.isDone()) {
try {
System.out.println(future.get());
break;
} catch (InterruptedException e) {
// ignored
} catch (ExecutionException e) {
// ignored
}
}
else {
try {
System.out.println("after " + sleepSeconds-- + " seconds, we will get future");
Thread.sleep(SECOND_MILLS);
} catch (InterruptedException e) {
// ignored
}
}
}
}
}
package com.ronniewang;

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 GetReturnValueFromCallable {

private static final int SLEEP_MILLS = 3000;

private static final int SECOND_MILLS = 1000;

private static int sleepSeconds = SLEEP_MILLS / SECOND_MILLS;

ExecutorService executorService = Executors.newCachedThreadPool();

/**
* 在创建多线程程序的时候，我们常实现Runnable接口，Runnable没有返回值，要想获得返回值，Java5提供了一个新的接口Callable
*/
public static void main(String[] args) {

new GetReturnValueFromCallable().testCallable();
}

private void testCallable() {

/**
* Callable需要实现的是call()方法，而不是run()方法，返回值的类型有Callable的类型参数指定，
* Callable只能由ExecutorService.submit() 执行，正常结束后将返回一个future对象
*/
Future<String> future = executorService.submit(new Callable<String>() {

public String call() throws Exception {

Thread.sleep(SLEEP_MILLS);
return "I from callable";
}
});

while (true) {
/**
* 获得future对象之前可以使用isDone()方法检测future是否完成，完成后可以调用get()方法获得future的值，
* 如果直接调用get()方法，get()方法将阻塞值线程结束
*/
if (future.isDone()) {
try {
System.out.println(future.get());
break;
} catch (InterruptedException e) {
// ignored
} catch (ExecutionException e) {
// ignored
}
}
else {
try {
System.out.println("after " + sleepSeconds-- + " seconds, we will get future");
Thread.sleep(SECOND_MILLS);
} catch (InterruptedException e) {
// ignored
}
}
}
}
}

输出结果：
after 3 seconds, we will get future
after 2 seconds, we will get future
after 1 seconds, we will get future
I from callable