异常java.lang.IllegalMonitorStateException

今天写代码遇到一个异常java.lang.IllegalMonitorStateException，百度问题，搜索blog得知

JavaDoc上关于IllegalMonitorStateException的解释是：
Thrown to indicate that a thread has attempted to wait on an object’s monitor or to notify other threads waiting on an object’s monitor without owning the specified monitor.
看起来有些晦涩难懂，比如object’s monitor。其实，在Object.notify()这个函数的JavaDoc中有相关的解释：
A thread becomes the owner of the object’s monitor in one of three ways:
1). By executing a synchronized instance method of that object.
2). By executing the body of a synchronized statement that synchronizes on the object.
3). For objects of type Class, by executing a synchronized static method of that class. ---------------------
作者：historyasamirror
来源：CSDN
原文：https://blog.csdn.net/historyasamirror/article/details/6709693