ListenableFuture和countdownlatch使用example

ListenableFuture可以允许你注册回调方法(callbacks)，在运算（多线程执行）完成的时候进行调用, 或者在运算（多线程执行）完成后立即执行

import com.google.common.util.concurrent.*;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * 如果需要所有的listenableFuture返回结果，可以使用countdownlatch，在Futures.addCallback的success里面把countdownlatch减1
 * 等countdownlatch=0的时候，所有的listenableFuture都计算完成
 */
public class ListenableFutureLearn2 {

    public void test3() throws Exception {
        ListeningExecutorService executorService = MoreExecutors.listeningDecorator(Executors.newCachedThreadPool());
        // 执行任务
        final ListenableFuture<String> listenableFuture = executorService.submit(new Callable<String>() {
            public String call() throws Exception {
                for (int i = 0; i < 10000; i++) {
                    System.out.println(i);
                }
                return "success";
            }

        });
        final ListenableFuture<String> listenableFuture2 = executorService.submit(new Callable<String>() {
            public String call() throws Exception {
                for (int i = 0; i < 10000; i++) {
                    System.out.println(-i);
                }
                return "success";
            }

        });
        // 绑定任务以及回调函数
        Futures.addCallback(listenableFuture, new FutureCallback<String>() {
                    @Override
                    public void onSuccess(String result) {
                        String str = "";
                        try {
                            str = listenableFuture.get();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        } catch (ExecutionException e) {
                            e.printStackTrace();
                        }
                        System.out.println("integer：" + str);
                        System.out.println("result：" + result);
                    }

                    @Override
                    public void onFailure(Throwable t) {
                        System.out.println("error" + t.getMessage());
                    }
                }
                , MoreExecutors.directExecutor());

        Futures.addCallback(listenableFuture2, new FutureCallback<String>() {
                    @Override
                    public void onSuccess(String result) {
                        String str = "";
                        try {
                            str = listenableFuture.get();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        } catch (ExecutionException e) {
                            e.printStackTrace();
                        }
                        System.out.println("integer：" + str);
                        System.out.println("result：" + result);
                    }

                    @Override
                    public void onFailure(Throwable t) {
                        System.out.println("error" + t.getMessage());
                    }
                }
                , MoreExecutors.directExecutor());
        TimeUnit.MILLISECONDS.sleep(500);
        System.out.println("listenableFuture:" + listenableFuture.get());
    }

    public static void main(String[] args) throws Exception {
        new ListenableFutureLearn2().test3();
    }
}
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