Java synchronized使用的正确事例和错误事例

叁歲伎倆 2022-08-18 03:12 170阅读 0赞

错误事例

package com.kunpengku;
    
    import java.util.Random;
    import java.util.Stack;
    
    public class Welcome { 
    
        public static Stack<Integer> abc = new Stack();
        public static void main(String[] args) throws Exception
        {
    
            for (int i=0;i<10;i++){
                abc.push(i);
            }
            //多线程方式二
            Q q = new Q();
            Q q2 = new Q();
            q.start();
            q2.start();
    
        }
    
    }
    class Base{
    
        public static Stack<Integer> abc;
    
        Base(){
            this.abc = Welcome.abc;
        }
        public void work(){
            int tmp;
            while(true){
                tmp = getint();
                if (tmp < 0)
                    break;
                System.out.println(Thread.currentThread() + String.valueOf(tmp));
            }
        }
    
        public synchronized int getint(){
            try{
                if(!abc.empty()){
    
                    Random random = new Random();
                    Thread.sleep(random.nextInt(1000));
    
                    int tmp = abc.pop();
    
                    return  tmp;
                }
                else{
                    return -1;
                }
    
            }catch(InterruptedException e){
                e.printStackTrace();
                return -2;
            }
    
    
        }
    
    }
    
    class Q extends Thread{
    
        public void run(){
    
            Base b = new Base();
            b.work();
        }
    
    
    }
    
    //错误事例

正确事例

package com.kunpengku;
    
    import java.util.Random;
    import java.util.Stack;
    
    public class Welcome { 
    
        public static Stack<Integer> abc = new Stack();
        public static void main(String[] args) throws Exception
        {
    
            for (int i=0;i<10;i++){
                abc.push(i);
            }
            //多线程方式二
            Q q = new Q();
            Q q2 = new Q();
            q.start();
            q2.start();
    
        }
    
    }
    class Base{
    
        public static Stack<Integer> abc;
    
        Base(){
            this.abc = Welcome.abc;
        }
        public void work(){
            int tmp;
            while(true){
                tmp = getint();
                if (tmp < 0)
                    break;
                System.out.println(Thread.currentThread() + String.valueOf(tmp));
            }
        }
    
        public synchronized static int getint(){
            try{
                if(!abc.empty()){
    
                    Random random = new Random();
                    Thread.sleep(random.nextInt(1000));
    
                    int tmp = abc.pop();
    
                    return  tmp;
                }
                else{
                    return -1;
                }
    
            }catch(InterruptedException e){
                e.printStackTrace();
                return -2;
            }
    
    
        }
    
    }
    
    class Q extends Thread{
    
        public void run(){
    
            Base b = new Base();
            b.work();
        }
    
    
    }
    
    //正确事例

这两个事例，其实就差一句代码

正确的是这样的， 类的静态方法  
public synchronized static int getint()\{

错误的是这样的 ， 类的非静态方法  
public synchronized int getint()\{