如何运行并行使用多个方法并在 java 中获取每个方法的输出

Question

我想运行并行使用三种不同的方法来提高 Java 中的性能。我还需要从他们三个那里得到输出。下面是我试过的示例。在这里，我不确定如何检索返回的字符串值。请帮我添加（将所有三个字符串连接到总数）。

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class test {

    public static void main(String[] args) {
        String total = "";

        Callable<String> callable1 = new Callable<String>()
        {
            @Override
            public String call() throws Exception
            {
                String t1 = "";
                t1 = method1();
                return t1;
            }
        };

        Callable<String> callable2 = new Callable<String>()
        {
            @Override
            public String call() throws Exception
            {
                String t2 = method2();
                return t2;
            }
        };

        Callable<String> callable3 = new Callable<String>()
        {
            @Override
            public String call() throws Exception
            {
                String t3 = method3();
                return t3;
            }
        };

        List<Callable<String>> taskList = new ArrayList<Callable<String>>();
        taskList.add(callable1);
        taskList.add(callable2);
        taskList.add(callable3);

        ExecutorService executor = Executors.newFixedThreadPool(3);

        try
        {
            executor.invokeAll(taskList);
            //total = ;(want to concatenate all the strings here).

            System.out.println(total);
        }
        catch (InterruptedException ie)
        {
            //do something if you care about interruption;
        }

    }
    public static String method1()
    {
        System.out.println("method1");
        return "1";

    }

    private static String method2()
    {
        System.out.println("method2");
        return "2";
    }

    private static String method3()
    {
        System.out.println("method3");
        return "3";
    }


}

Answer 1

因为taskList是一个List<Callable<String>>，executor.invokeAll(taskList) returns一个List<Future<String>>包含一个Future<String>对应于[=11中的每个任务=].您需要保存 List<Future<String>> 以便稍后可以获取任务结果。像这样：

List<Future<String>> futureList = executor.invokeAll(tasklist);
String result = futureList.get(0).get() +
                futureList.get(1).get() +
                futureList.get(2).get();

除了InterruptedException，Future.get()还可以抛出CancellationException和ExecutionException所以你需要准备好在你的try中处理这些块。

Answer 2

由于您的任务数量很少，您可以创建 3 个 CompletableFutures 并流过它并加入它。

CompletableFuture<String> task1 = CompletableFuture.supplyAsync(() -> method1());
CompletableFuture<String> task2 = CompletableFuture.supplyAsync(() -> method2());
CompletableFuture<String> task3 = CompletableFuture.supplyAsync(() -> method3());

String concate = Stream.of(task1, task2, task3)
        .map(CompletableFuture::join)
        .reduce("", (s1, s2) -> s1 + s2);
System.out.println(concate);

Answer 3

在@Govinda 回答之上添加 - 您可以使用 supplyAsync 工厂方法创建 CompletableFuture 的 Stream，并通过调用 CompletableFuture::join 完成并通过调用 [=concat Collectors.joining().

CompletableFuture<String> task1 = CompletableFuture.supplyAsync(Test::method1);      
CompletableFuture<String> task2 = CompletableFuture.supplyAsync(Test::method2);      
CompletableFuture<String> task3 = CompletableFuture.supplyAsync(Test::method3);      
                                                                                              
String concat =                                                                               
    Stream.of(task1, task2, task3).map(CompletableFuture::join).collect(Collectors.joining());

System.out.println(concat);

如何运行并行使用多个方法并在 java 中获取每个方法的输出

How to run multiple methods parallely and get outputs from each of them in java

java

parallel-processing

multithreading

callable

completable-future

如何 运行 并行使用多个方法并在 java 中获取每个方法的输出

How to run multiple methods parallely and get outputs from each of them in java

java

parallel-processing

multithreading

callable

completable-future

如何运行并行使用多个方法并在 java 中获取每个方法的输出