Java interview questions: - Elaborate different types of inner classes?
Following are the different types of inner classes in Java interview questions.
Nested top-level classes-
- If you declare a class within a class and specify the static modifier, the compiler treats the class just like any other top-level class
- Any class outside the declaring class accesses the nested class with the declaring class name acting similarly to a package. eg, outer. Inner
- Top-level inner classes implicitly have access only to static variables. There can also be inner interfaces. All of these are of the nested top-level variety.
Member classes -
- Member inner classes are just like other member methods and member variables and access to the member class is restricted, just like methods and variables.
- This means a public member class acts similarly to a nested top-level class
- The primary difference between member classes and nested top-level classes is that member classes have access to the specific instance of the enclosing class.
Local classes-
- Local classes are like local variables, specific to a block of code. Their visibility is only within the block of their declaration. In order for the class to be useful beyond the declaration block, it would need to implement a more publicly available interface.
- Because local classes are not members, the modifiers public, protected, private, and static are not usable.
Anonymous classes-
- Anonymous inner classes extend local inner classes one level further. As anonymous classes have no name, you cannot provide a constructor
- Anonymous class is a class defined inside a method without a name and is instantiated and declared in the same place and cannot have explicit constructors
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