4.脏读

对于对象的同步、异步的方法，设计程序的时候一定要考虑问题的整体，出现数据不一致就一个经典的错误。

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，需要考虑功能业务的整体性，同时为set、get加锁，使用 synchronized 关键字，保证业务的原子性，不然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();
    }
}
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