lang:java:nested_class

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The Java programming language allows you to define a class within another class.

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Nested or Inner ?

Nested classes that are declared static are called static nested classes.
Non-static nested classes are called inner classes and requires an instance of the outer class to be referenced.

class OuterClass {
    ...
    static class StaticNestedClass {
        ...
    }
    class InnerClass {
        ...
    }
}

When to use ?

If a class is useful to only one other class, then it is logical to embed it in that class and keep the two together.
It increases encapsulation but increase dependency

<wrap>If you want to implement an hierarchy like of object see also Tree - Composite Type (Design Pattern)</note>

Documentation / Reference

Nested Classes