Java Nested Classes Overview

Study Notes

Nested Classes

A nested class is defined as a class within another class.
The outer class is responsible for enclosing the nested class.

Syntax of Nested Classes

An example of nested class syntax is:

class Outer_Demo {
    class Nested_Demo {
    }
}

Types of Nested Classes

Nested classes can be categorized into two main types:
- Non-static nested classes: These function as non-static members of a class.
- Static nested classes: These act as static members of a class.

Inner Classes (Non-static Nested Classes)

Inner classes fall into three distinct categories depending on their definition location:
- Inner Class: A standard inner class defined within another class.
- Method-local Inner Class: An inner class that can only be instantiated in the method where it is defined.
- Anonymous Inner Class: An inner class without a specified name, created for immediate instantiation, typically for overriding methods.

Characteristics of Inner Classes

An inner class can be declared as private, limiting its access to instances outside of the containing class.

Method-local Inner Class

This type of inner class can be defined and instantiated exclusively within the scope of a specific method, restricting its visibility.

Anonymous Inner Class

An anonymous inner class is declared without a name.
It can be both declared and instantiated at the same time, making it useful for quickly overriding methods from a class or interface.

Static Nested Class

A static nested class acts as a static member of the outer class.
It can be accessed directly without needing to instantiate the outer class.
Unlike non-static inner classes, static nested classes do not have access to instance variables and methods of the outer class.

Description

This quiz covers the concept of nested classes in Java, including their syntax and the different types. Learn about inner classes, method-local inner classes, and anonymous inner classes as part of understanding how these classes function within an outer class. Test your knowledge on the definitions and examples provided.