Java多线程练习题

 题目1

设置4个线程对象，其中两个实现自减操作，两个实现自增操作

 知识点，1.可以利用volatile实现直接对内存操作无需数据备份。2.可以利用synchronized实现同步防止线程出现数据混乱问题。3.通过join函数实现线程之间阻塞保证线程的执行顺序

package Test1401;
//线程自增
class Decrease implements Runnable {
    private volatile int num = 100;
    @Override
    public void run() {
        synchronized (this) {
            while (num > 0) {
                num--;
                System.out.println(num);
            }
        }
    }
}
//线程自减
class Increase implements Runnable {
    private volatile int number = 0;
    @Override
    public void run() {
        synchronized (this) {
            while (number < 100) {
                number++;
                System.out.println(number);
            }
        }
    }
}
public class javaDemo {
    public static void main(String[] args) {
        Decrease d1 = new Decrease();
        Decrease d2 = new Decrease();
        Increase i1 = new Increase();
        Increase i2 = new Increase();

        Thread Thread1 = new Thread(d1);
        Thread Thread2 = new Thread(d2);
        Thread Thread3 = new Thread(i1);
        Thread Thread4 = new Thread(i2);
//        线程启动
        Thread1.start();
        Thread2.start();
        Thread3.start();
        Thread4.start();
//       线程阻塞队列
        try {
        Thread1.join();