脏读
对于对象的同步和异步方法,我们在设计自己的程序的时候,一定要考虑问题的整体性,不然会出现数据不一致的错误,很经典的错误就是脏读(dirtyRead)
public class DirtyRead { private String username = "bjsxt"; private String password = "123"; public synchronized void setValue(String username, String password){ this.username = username; try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } this.password = password; System.out.println("setValue最终结果:username = " + username + " , password = " + password); } public void getValue(){ System.out.println("getValue方法得到:username = " + this.username + " , password = " + this.password); } public static void main(String[] args) throws Exception{ final DirtyRead dr = new DirtyRead(); Thread t1 = new Thread(new Runnable() { @Override public void run() { dr.setValue("z3", "456"); } }); t1.start(); Thread.sleep(1000); dr.getValue(); } 结果: getValue方法得到:username = z3 , password = 123 setValue最终结果:username = z3 , password = 456
结果分析: 预计需要的结果是username = z3 , password = 456 但是没有,为了保持业务的原子性,setValue时不需要getValue,需要在getValue方法上加上synchronized关键字,不然会出现业务错误