• Java进阶知识查漏补缺05


    Java线程死锁:

    package com.cjf.ThreadAppl;
    
    /**
     * Created with IntelliJ IDEA.
     * Description:
     * Author: Everything
     * Date: 2020-07-01
     * Time: 20:48
     */
    //死锁问题
    public class DeadLockTest {
    
        public static void main(String[] args) {
    
            StringBuffer s1 = new StringBuffer();
            StringBuffer s2 = new StringBuffer();
    
            new Thread(){
                @Override
                public void run() {
                    synchronized (s1){
                        s1.append("a");
                        s2.append("1");
    
                        try {
                            sleep(1000);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        synchronized (s2){
                            s1.append("b");
                            s2.append("2");
    
                            System.out.println(s1);
                            System.out.println(s2);
                        }
                    }
                }
            }.start();
    
    
            new Thread(new Runnable() {
                @Override
                public void run() {
                    synchronized (s2) {
                        s1.append("c");
                        s2.append("3");
    
                        try {
                            Thread.sleep(1000);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
    
                        synchronized (s1) {
                            s1.append("d");
                            s2.append("4");
    
                            System.out.println(s1);
                            System.out.println(s2);
                        }
                    }
                }
            }).start();
        }
    }

    解决Java线程死锁,改进懒汉式单例模式

    package com.cjf.ThreadAppl;
    
    /**
     * Created with IntelliJ IDEA.
     * Description:
     * Author: Everything
     * Date: 2020-07-01
     * Time: 20:23
     */
    
    //改进懒汉式单例模式
    public class SingletonSenior {
    
    }
    
    class Bank{
        private Bank(){
    
        }
    
        private static Bank instance = null;
    
        public static  Bank getInstance() {
            //这种方式,会让后面的进程一直重复无用的判断工作,当前已经不能创建新的对象,直接进入return效率会更高
    //        synchronized (Bank.class) {
    //            if (instance == null) {
    //                instance = new Bank();
    //            }
    //            return instance;
    //        }
            //下面这种效率高
            if(instance == null){
                synchronized (Bank.class) {
                if (instance == null) {
                    instance = new Bank();
                }
            }
            }
            return instance;
        }
    }

    使用Lock锁解决线程安全问题

    package com.cjf.ThreadAppl;
    
    import sun.security.krb5.internal.Ticket;
    
    import javax.swing.plaf.SliderUI;
    import java.util.concurrent.locks.ReentrantLock;
    
    /**
     * Created with IntelliJ IDEA.
     * Description:
     * Author: Everything
     * Date: 2020-07-01
     * Time: 21:12
     */
    
    //jdk5以后加入
    //方法三:使用Lock锁解决线程安全问题
    class Window implements Runnable{
        private int ticket=100;
    
        //实例化一个ReentrantLock锁
        private ReentrantLock lock = new ReentrantLock();
    
        @Override
        public void run() {
            while (true){
                try {
                    //调用锁定方法lock
                    lock.lock();
                    if(ticket > 0){
                        try {
                            Thread.sleep(10);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        ticket--;
                        System.out.println(Thread.currentThread().getName()+"售出票,余票"+ticket+"张");
                    }else {
                        break;
                    }
                }finally {
                    //调用解锁方法
                    lock.unlock();
                }
            }
        }
    }
    
    
    
    
    public class LockTest {
        public static void main(String[] args) {
            Window window1 = new Window();
            Thread thread1 = new Thread(window1);
            Thread thread2 = new Thread(window1);
            Thread thread3 = new Thread(window1);
            thread1.setName("窗口一");
            thread2.setName("窗口二");
            thread3.setName("窗口三");
            thread1.start();
            thread2.start();
            thread3.start();
        }
    }
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  • 原文地址:https://www.cnblogs.com/cuijunfeng/p/13222431.html
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