java面试题--4个线程两个线程每次对j增加1另外两个线程对j每次减少1

来源：互联网发布：python界面开发html5 编辑：程序博客网时间：2024/06/06 07:25

//方法一

public class ThreadTest1 {
    private int j;
    public static void main(String args[]) {
        ThreadTest1 tt = new ThreadTest1();
        Inc inc = tt.new Inc();
        Dec dec = tt.new Dec();
        for (int i = 0; i < 2; i++) {
            Thread t = new Thread(inc);
            t.start();
            t = new Thread(dec);
            t.start();
        }
    }

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

    private synchronized void dec() {
        j--;
        System.out.println(Thread.currentThread().getName() + "-dec:" + j);
    }

    class Inc implements Runnable {
        public void run() {
            for (int i = 0; i < 5; i++) {
                inc();
            }
        }
    }

    class Dec implements Runnable {
        public void run() {
            for (int i = 0; i < 5; i++) {
                dec();
            }
        }
    }
}
//方法二
// ----------随手再写的一个-------------
public class A {
    JManager j = new JManager();

    public static void main() {
        new A().call();
    }

    void call() {
        for (int i = 0; i < 2; i++) {
            new Thread(new Runnable() {
                public void run() {
                    while (true) {
                        j.accumulate();
                    }
                }
            }).start();
            new Thread(new Runnable() {
                public void run() {
                    while (true) {
                        j.subtract();
                    }
                }
            }).start();
        }
    }
}

class JManager {
    private int j = 2;

    public synchronized void subtract() {
        j--;
    }

    public synchronized void accumulate() {
        j++;
    }

}