问题描述
我想并行运行三种不同的方法来提高Java的性能。另外,我还需要从它们三个中获取输出。以下是我尝试过的示例。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在一起)。
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";
}
}
解决方法
由于taskList
是List<Callable<String>>
,executor.invokeAll(taskList)
返回一个List<Future<String>>
,其中包含与Future<String>
中的每个任务相对应的taskList
。您需要保存该List<Future<String>>
,以便以后获得任务结果。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
,因此您需要准备在try
块中处理它们。
由于任务数量很少,因此可以创建3个CompletableFutures
并流式传输并加入它。
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);
,
在@Govinda答案之上添加-
您可以使用Stream
工厂方法创建CompletableFuture
个supplyAsync
,并通过调用CompletableFuture::join
complete 来创建它们,并通过调用{{1} }。
Collectors.joining()