互联网并发编程之一 线程安全03线程中的脏读

当一个线程运行修改数据的方法，另一个线程启动读取数据的值，会读到未修改的前的数据

package com.jc.thread;public class Thread04 {private String name = "abc";private String password = "123";public synchronized void setValue(String name, String password) {try {Thread.sleep(2000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}this.name = name;this.password = password;}public void getValue() {System.out.println(this.name);System.out.println(this.password);}public static void main(String[] args) {final Thread04 thread04 = new Thread04();Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {thread04.setValue("jkl", "333");}}, "t1");t1.start();try {Thread.sleep(1000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}thread04.getValue();}}

输出结果为：

abc
123

对于对象的同步或者异步方法，我们在设计程序的时候一定要考虑整体性，不然会出现不一致的问题，很经典的错误就是脏读，当setValue()和getValue()同时加上synchronized 关键字，保证了业务的原子性。

package com.jc.thread;


public class Thread04 {


private String name = "abc";
private String password = "123";


public synchronized void setValue(String name, String password) {

try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
this.name = name;
this.password = password;
}


public synchronized void getValue() {
System.out.println(this.name);
System.out.println(this.password);
}


public static void main(String[] args) {


final Thread04 thread04 = new Thread04();
Thread t1 = new Thread(new Runnable() {


@Override
public void run() {

thread04.setValue("jkl", "333");
}
}, "t1");
t1.start();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
thread04.getValue();
}


}

输出结果为：

jkl
333