Question

我的目标是启动三个未同步的线程，并让它们各添加一千个元素。这些元素需要存储在一个集合中（我选择了Vector），然后打印出来。出于某种原因，我没有得到要打印的元素。我在尝试解决打印方法和创建元素的方法时遇到了麻烦。任何帮助表示赞赏。

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import java.util.Vector;

public class MyRun implements Runnable{
    int global = 0;
    //create sets
    static Vector t1v = new Vector();
    static Vector t2v = new Vector();
    static Vector t3v = new Vector();           
    public void run() {
        action1();
    }
    public void action1() {
        for(int i = 0; i < 1000; i++) {
            global++;
            int x = global;
            String tName = Thread.currentThread().getName();
            if(tName == "t1") {
                t1v.addElement(x);
                System.out.println(t1v.elementAt(x));
            }
            if(tName == "t2") {
                t2v.addElement(x);
            }
            if(tName == "t3") {
                t3v.addElement(x);
            }           
            //System.out.println("thread: " + tName  + "counter is: " + global);
        }   
        }
    public static Vector gett1v() {
        return t1v;
    }

    public static Vector gett2v() {
        return t2v;
    }

    public static Vector gett3v() {
        return t3v;
    }

}

class ThreadTest{

    public static void main(String[] args) {
        //create threads
        Runnable threadJob = new MyRun();
        Thread t1 = new Thread(threadJob);
        t1.setName("thread1");
        Thread t2 = new Thread(threadJob);
        t2.setName("thread2");
        Thread t3 = new Thread(threadJob);
        t3.setName("thread3");


        t1.start();
        t2.start();
        t3.start();

        Vector th1v = MyRun.gett1v();
        Vector th2v = MyRun.gett2v();
        Vector th3v = MyRun.gett3v();
        //MyRun.printSets();
        for(int i=0; i < th1v.size(); i++) {
            System.out.println("Thread 1: " + th1v.elementAt(i));
        }

        for(int i=0; i < th2v.size(); i++) {
            System.out.println("Thread 2: " + th2v.elementAt(i));
        }


        for(int i=0; i < th3v.size(); i++) {
            System.out.println("Thread 3: " + th3v.elementAt(i));   
    }
    }
}

Answer 1

我冒昧地修改了你的代码。

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import java.util.Vector;
import java.util.concurrent.atomic.AtomicInteger;

public class MyRun implements Runnable{
    AtomicInteger global = new AtomicInteger(0);
    //create sets
    static Vector t1v = new Vector();
    static Vector t2v = new Vector();
    static Vector t3v = new Vector();           
    public void run() {
        action1();
    }
    public void action1() {
        for(int i = 0; i < 1000; i++) {
            global.incrementAndGet();
            int x = global.get();
            String tName = Thread.currentThread().getName();
            if(tName == "t1") {
                t1v.addElement(x);
            }
            if(tName == "t2") {
                t2v.addElement(x);
            }
            if(tName == "t3") {
                t3v.addElement(x);
            }           
            //System.out.println("thread: " + tName  + "counter is: " + global);
        }   
        }
    public static Vector gett1v() {
        return t1v;
    }

    public static Vector gett2v() {
        return t2v;
    }

    public static Vector gett3v() {
        return t3v;
    }

}

class ThreadTest{

    public static void main(String[] args) {
        //create threads
        Runnable threadJob = new MyRun();
        Thread t1 = new Thread(threadJob);
        t1.setName("t1");
        Thread t2 = new Thread(threadJob);
        t2.setName("t2");
        Thread t3 = new Thread(threadJob);
        t3.setName("t3");


        t1.start();
        t2.start();
        t3.start();

        try{
            t1.join();
            t2.join();
            t3.join();

        }catch(InterruptedException e){}
        Vector th1v = MyRun.gett1v();
        Vector th2v = MyRun.gett2v();
        Vector th3v = MyRun.gett3v();
        //MyRun.printSets();
        System.out.println(th1v.size()+" "+th2v.size()+" "+th3v.size());
        for(int i=0; i < th1v.size(); i++) {
            System.out.println("Thread 1: " + th1v.elementAt(i));
        }

        for(int i=0; i < th2v.size(); i++) {
            System.out.println("Thread 2: " + th2v.elementAt(i));
        }


        for(int i=0; i < th3v.size(); i++) {
            System.out.println("Thread 3: " + th3v.elementAt(i));   
    }
    }
}

注意事项：

主线程独立于t1，t2，t3线程，所以如果你想获取结果使用join（）或使用FutureTask或 ExecutorService.submit（Runnable r）。所以主线程将等待所有三个线程完成然后执行for循环。由于主线程没有等待，你的输出空了。
如果它们是多个mutator线程，则使用Atomic类型，但只有一个mutator线程，而且多个reader线程使用volatile关键字，但使用volatile关键字代价很高。

希望有所帮助!!

将元素添加到线程的向量并打印它们 - Java

1 个答案: