Question

我试图采用这样的for循环：

List<Object> users;

public void doSomething() {

    for (Object o : users) {

    // split up the for loop
    // and handle chunks of the iteration
    // across multiple threads

        o.doThis();
        o.doThat();
    }
}

将迭代for(Object o: users){分成多个线程。如何在不导致并发修改的情况下使用Java执行此操作。我的目标是将其扩展为线程池，因此List<Object> users;中的对象越多意味着处理迭代块的线程越多。

我是多线程的新手，并且不确定java utils可以帮助实现这一目标。

Answer 1

如果您使用的是java 8，那么流将是最简单的方式

users.parallelStream()
                .forEach(u -> { u.doThis(); u.doThat(); } );

您还可以实现一个可运行的接口，并创建一个ThreadExecutor。这比上面的例子要多得多。

Answer 2

You can use java.util.concurrent.Executors class which would assist you in executing multiple thread concurrently.

Have written a small method, which can assist your understanding.

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class SimpleThreadPool {
    public static void main(String[] args) {
        ExecutorService executor = Executors.newFixedThreadPool(5);
        for (int i = 0; i < 10; i++) {
            Runnable worker = new WorkerThread("" + i);
            executor.execute(worker);
          }
        executor.shutdown();
        while (!executor.isTerminated()) {

        }
        System.out.println("Finished all threads");
    }

}



public class WorkerThread implements Runnable {

    private String command;

    public WorkerThread(String s){
        this.command=s;
    }

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+" Start. Command = "+command);
        processCommand();
        System.out.println(Thread.currentThread().getName()+" End.");
    }

    private void processCommand() {
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    @Override
    public String toString(){
        return this.command;
    }
}

多线程for循环

2 个答案: