今天寫代碼遇到一個異常java.lang.IllegalMonitorStateException，百度問題，搜索blog得知
JavaDoc上關於IllegalMonitorStateException的解釋是：
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.
看起來有些晦澀難懂，比如object’s monitor。其實，在Object.notify()這個函數的JavaDoc中有相關的解釋：
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
來源：CSDN
原文：https://blog.csdn.net/historyasamirror/article/details/6709693