1、 准备两个待合并的映射表，示例中通过新建获取，实际应用时应从数据库或其它数据源读取所需数据。 2、 调用putAll方法合并map时，需先判断对象是否为null。为避免map01为null导致无法合并map02，应新建一个map实例来确保操作顺利执行。

A colleague of mine recently ran into an issue that I have not run into myself, but found to be interesting and, in my opinion, worth blogging about here. During some distributed Java development, my ...

Do you need to know how to sort Java objects in a collection, array, or map? Here's how to use the Comparable and Comparator interfaces and avoid ClassCastExceptions. Programmers frequently need to ...