java多线程之synchronized

Java多线程同步：使用synchronized实现循环打印

原创已于 2023-03-05 11:38:18 修改 · 325 阅读

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#java #多线程 #synchronized

于 2023-02-27 15:06:30 首次发布

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该文章演示了一个Java多线程程序，使用`synchronized`关键字确保线程安全。类`MultiThreadPrint`创建了多个线程（PrintThread），每个线程按顺序打印数字，从1到给定的最大值。线程间通过共享`lock`对象进行同步，当达到最大值时所有线程停止。

java多线程之synchronized

实现一个多线程循环打印的demo
代码：

public class MultiThreadPrint {
    private final int threadNum; //线程数
    private final int printTo; //打印的最大整数

    private int count = 0;
    private final Object lock = new Object();
    
    public static void main(String[] args) {
    	//运行示例
        new MultiThreadPrint(5, 100).threadsPrint();
    }
    
    public MultiThreadPrint(int threadNum, int printTo){
        if(threadNum < 1 || printTo < 1 || threadNum > printTo){
            throw new RuntimeException("错误参数");
        }
        this.threadNum = threadNum;
        this.printTo = printTo;
    }

    class PrintThread implements Runnable {
        int flag;

        public PrintThread (int flag){
            this.flag = flag;
        }

        @Override
        public void run() {
            synchronized (lock){
                while(true){
                    if(count == printTo){
                        lock.notifyAll();
                        return;
                    }else if(count % threadNum == flag){
                        System.out.println(Thread.currentThread().getName() + " " + ++count);
                        lock.notifyAll();
                    }else{
                        try {
                            lock.wait();
                        } catch (InterruptedException e) {
                            throw new RuntimeException(e);
                        }
                    }
                }
            }
        }
    }

    public void threadsPrint(){
        for (int i = 0; i < threadNum; i++) {
            new Thread(new PrintThread(i), "thread---"+i).start();
        }
    }
}