Nested Class, Member Class, Inner Class, Local Class, Anonymous Class, Top-level Class
1、top-level class
顶层类：不用解释
2、nested class
内嵌的顶层类 - nested (top-level) class：
A class defined as static inside another class. Instances can live
independent of instances of the enclosing class. It's a normal class,
just with a longer name.
就是：静态内部类，静态内部类就是一般的类，只是名字长一点而已（带上了外部类的前缀）
3、member class
成员内部类 - member (inner) class：
A class defined as non-static inside another class. Instances are
dependent on an instance of the enclosing class.
就是：非静态内部类，依赖外部类的实例。
4、local class
本地内部类 / 临时内部类 - local (inner) class：
Defined inside a code block, only visible inside that code block
就是：定义在代码块中的内部类，比如方法中定义的类。
5、anonymous class
匿名内部类 - anonymous (inner) class:
A local class without a name.
就是：一个没有名字的类。
6、inner class
内部类
A member, local or anonymous class
就是：包括了：成员内部类、本地内部类、匿名内部类。
refs: Nested Class, Member Class, Inner Class, Local Class, Anonymous Class