Nested Class

Nested class is a class defined inside another class.
Used to logically group classes, improve encapsulation and access outer class members.

Types of Nested Classes

Type	Static?	Can Access Outer Instance?	Common Use Case
Static Nested	✅	✗	Utility/helper class
Inner Class	✗	✅	tightly coupled object relationships
Local inner	✗	✅	Defined inside a method
Anonymous Class	✗	✅	One-off overrides (already covered)

Example

Static Nested Class

class Outer {
    static class Inner {
        void show() {
            System.out.println("Static Nested");
        }
    }
}
 
Outer.Inner obj = new Outer.Inner();
obj.show();

Non-Static (Inner) Class

class Outer {
    class Inner {
        void show() {
            System.out.println("Inner Class");
        }
    }
}
 
Outer outer = new Outer();
Outer.Inner inner = outer.new Inner();
inner.show();

Local Inner Class

class Outer {
    void display() {
        class Local {
            void msg() {
                System.out.println("Local Inner Class");
            }
        }
        
        Local local = new Local();
        local.msg();
    }
}

Key Points

• Inner classes can access all members (even private) of the outer class.
• Static nested classes cannot access non-static members directly.
• Helps keep code organized and logically grouped.

Tip

If you’re asked about class organization or encapsulation, mention nested classes as a clean way to group related logic.

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Parent: _OOP Advanced Tools