4.脏读

对于对象的同步、异步的方法，设计程序的时候必定要考虑问题的总体，出现数据不一致就一个经典的错误。

   
   
   
   
   

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    

    
    
    
    
    
正确结果输出：private synchronized void getUserValue()
    
    
    
    
    
setValue 最终结果->：user = testuser pwd = 111111 getUserValue 设置值：user = testuser pwd = 111111

    
    
    
    
    


    
    
    
    
    
错误结果输出：private void getUserValue() 属于异步调用
    
    
    
    
    
getUserValue 设置值：user = testuser pwd = 123456 setValue 最终结果->：user = testuser pwd = 111111
   
   
   
   
   
package demo1;/** *  * Created by liudan on 2017/6/3. */public class MyThread4 { private String user = "liudan"; private String pwd = "123456"; private synchronized void setUserValue(String user, String pwd) { this.user = user; try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } this.pwd = pwd; System.err.println("setValue 最终结果->：user = " + user + "\t" + "pwd = " + pwd); } private void getUserValue() { System.err.println("getUserValue 设置值：user = " + this.user + "\t" + "pwd = " + this.pwd); } /** * 对一个方法枷加锁，须要考虑功能业务的总体性，同时为set、get加锁，使用 synchronized 关键字，保证业务的原子性，否则则会出现业务的错误。 * @param args * @throws InterruptedException */ public static void main(String[] args) throws InterruptedException { final MyThread4 tUser = new MyThread4(); Thread userThread = new Thread(new Runnable() { @Override public void run() { tUser.setUserValue("testuser","111111"); } }); userThread.start(); Thread.sleep(1000); tUser.getUserValue(); }}