实现一个线程安全的计数器

梦里梦外; 2023-06-25 02:28 7阅读 0赞

package com.test;
    
    
    public class MySafeThread implements Runnable{
    
        public static volatile int a;
    
        @Override
        public void run(){
            while (true){
                try {
                    Thread.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                MySafeThread.calc();
            }
        }
        //计数 注意加锁sychronized
        private synchronized static void calc(){
    
            if (a<1000){
                a=++a;
                //现场名称与自增后的值
                System.out.println(Thread.currentThread().getName()+":"+a);
            }
        }
        //开启五个线程进行计数
        public static void main(String[] args) {
            for (int i=0;i<5;i++){
                MySafeThread mySafeThread = new MySafeThread();
                Thread t = new Thread(mySafeThread);
                t.start();
            }
        }
    }

第二种方法：

package com.test;
    
    
    import java.util.concurrent.locks.ReentrantLock;
    
    public class MySafeThread implements Runnable{
    
        public static volatile int a;
        static ReentrantLock lock = new ReentrantLock();
    
        @Override
        public void run(){
            while (true){
                try {
                    Thread.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                MySafeThread.calc();
            }
        }
        //计数 注意加锁sychronized
        private  static void calc(){
            lock.lock();
            try{
                if (a<1000){
                    a=++a;
                    //现场名称与自增后的值
                    System.out.println(Thread.currentThread().getName()+":"+a);
                }
            }catch(Exception e){
                e.printStackTrace();
            }finally {
                lock.unlock();
            }
    
    
        }
        //开启五个线程进行计数
        public static void main(String[] args) {
            for (int i=0;i<5;i++){
                MySafeThread mySafeThread = new MySafeThread();
                Thread t = new Thread(mySafeThread);
                t.start();
            }
        }
    }