Java Concurrency in Practice ：基础知识（重排序与可见性）

重排序 与 可见性

1、小段代码片

public class NoVisibility{
private static boolean ready;
private static int number;
private static class ReaderThread extends Thread{
public void run(){
while(!ready)
Thread.yield();
System.out.println(number);
}
}
public static void main(String[] args){
new ReaderThread().start();
number = 42;
ready = true;
}
}

2、输出结果解释

3、如何防止错误结果的发生（加锁与可见性）

public class Visibility{
private static volatile boolean ready;
private static int number;
private static class ReaderThread extends Thread{
public void run(){
while(!ready)
Thread.yield();
System.out.println(number);
}
}
public static void main(String[] args){
new ReaderThread().start();
number = 42;
ready = true;
}
}

4、输出结果分析