设计4个线程,其中两个线程每次对j增加1,另外两个线程对j每次减少1.写出程序....-优快云博客

本文提供了一个使用Java实现的线程同步示例，通过synchronized关键字确保了add和inc方法在同一时刻只能被一个线程访问，展示了如何创建自定义的线程类并启动多个线程来增加和减少共享变量。

/**
 * @author WenQiang Wu
 * @version Dec 28, 2009
 */
public class ThreadTest {

    private int j;

    /**
     * add method
     */
    private synchronized void add() {
        j++;
        System.out.println(Thread.currentThread().getName() + "->add : " + j);
    }

    /**
     * inc method
     */
    private synchronized void inc() {
        j--;
        System.out.println(Thread.currentThread().getName() + "->inc : " + j);
    }

    /**
     * 
     * @param args
     */
    public static void main(String[] args) {
        ThreadTest tt = new ThreadTest();

        //inner class instance
        Inc inc = tt.new Inc();
        Add add = tt.new Add();

        //start thread
        for (int i = 0; i < 2; i++) {
            //start inc thread
            Thread thread = new Thread(inc);
            thread.start();

            //start add thread
            thread = new Thread(add);
            thread.start();
        }
    }

    /**
     * 
     * @author WenQiang Wu
     * @version Dec 28, 2009
     */
    class Inc implements Runnable {
        /*
         * (non-Javadoc)
         * 
         * @see java.lang.Runnable#run()
         */
        public void run() {
            for (int i = 0; i < 100; i++) {
                inc();
            }
        }
    }

    /**
     * 
     * @author WenQiang Wu
     * @version Dec 28, 2009
     */
    class Add implements Runnable {

        /* (non-Javadoc)
         * @see java.lang.Runnable#run()
         */
        public void run() {
            for (int i = 0; i < 100; i++) {
                add();
            }
        }
    }
}