How can I call methods simultaneously in Java?

问题

I need to make a program in Java for a class I am in, but I need to be able to make 6 methods execute at once. I have no idea how to go about this, but here is a small bit of what I have:

public static void main(String[] args) {
    method1();
    method2();
    method3();
    method4();
    method5();
    method6();
}

This just plays the methods one at a time, and I need them all at once.

回答1:

Make use of multiple threads, although you should read up on concurrency if you're going to edit the same objects from multiple threads.

public static void main(String[] args) {
    new Thread() { 
        public void run() {
            method1();
        }
    }.start();
    new Thread() { 
        public void run() {
            method2();
        }
    }.start();
    //etc

    //or, as kingdamian42 pointed out, if you use java8, use this
    new Thread(() -> method1()).start();
    new Thread(() -> method2()).start();
}

回答2:

As @kevin-cruijssen said you can use something like this:

public static void main(String[] args) {
    Arrays.asList(new Thread(() -> method1()), new Thread(() -> method2()))
        .parallelStream().forEach(x -> x.start());
}

But you have no guarantee on the execution order.

回答3:

An full example of how to do this can be achieved if your machine has 6CPU

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

    public class demo {
    private int count1 = 0;
    private int count2 = 0;
    private int count3 = 0;
    private int count4 = 0;
    private int count5 = 0;
    private int count6 = 0;

    int countA() {
        for (int i = 0; i < 1000; i++) {
            count1++;
        }
        System.out.println(count1);
        return count1;
    }

    int countB() {
        for (int i = 0; i < 1000; i++) {
            count2++;
        }
        System.out.println(count2);
        return count2;
    }

    int countC() {
        for (int i = 0; i < 1000; i++) {
            count3++;
        }
        System.out.println(count3);
        return count3;
    }

    int countD() {
        for (int i = 0; i < 1000; i++) {
            count4++;
        }
        System.out.println(count4);
        return count4;
    }

    int countE() {
        for (int i = 0; i < 1000; i++) {
            count5++;
        }
        System.out.println(count5);
        return count5;
    }

    int countF() {
        for (int i = 0; i < 1000; i++) {
            count6++;
        }
        System.out.println(count6);
        return count6;
    }

    public void execute() {
        ExecutorService executorService = Executors.newFixedThreadPool(6);

        // method reference introduced in Java 8
        executorService.submit(this::countA);
        executorService.submit(this::countB);
        executorService.submit(this::countC);
        executorService.submit(this::countD);
        executorService.submit(this::countE);
        executorService.submit(this::countF);

        // close executorService
        executorService.shutdown();
    }

    public static void main(String[] args) {
        new demo().execute();
    }

}

来源：https://stackoverflow.com/questions/25386839/how-can-i-call-methods-simultaneously-in-java

标签

java

methods