Core java - Advance Topics
  • Welcome
  • Schedule
  • 1) Exception Handling
    • 1) Introduction to Exception Handling
    • 2) Categories of Exceptions
    • 3) Creating a method that throws an exception
    • 4) Creating Custom Exception Classes
    • 5)What happens when an exception is thrown?
      • 5.1) Creating try-catch-finally blocks
      • 5.2) Using a method that throws a checked exception
      • 5.3) Using a method that throws a runtime exception
      • 5.4) Using a method that throws an error
      • 5.5) Will a finally block execute even if the catch block defines a return statement?
      • 5.6) What happens if both a catch and a finally block define return statement?
      • 5.7) What happens if a finally block modifies the value returned from a catch block?
      • 5.8) Can a try block be followed only by a finally block?
      • 5.9) Does the order of the exceptions caught in the catch blocks matter?
      • 5.10) Can I rethrow an exception or the error I catch?
      • 5.11) Can I declare my methods to throw a checked exception instead of handling it?
      • 5.12) I can create nested loops, so can I create nested try-catch blocks too?
      • 5.13) Should I handle errors?
    • 6) Best Practices
    • 7) Cheat Sheet
    • 8) Problems
  • 2) Wrapper Classes and Enums
    • 2.1) Creating objects of the wrapper classes
    • Enums
  • 3) Inner Classes
    • 3.1) Static nested class (also called static inner class)
    • 3.2) Inner class (also called member class)
    • 3.3) Anonymous inner class
    • 3.4) Method local inner classes
    • CheatSheet
  • 4) Generics
    • Multiple Type parameters in Generic classes
    • Inheritance using Generics
    • Generic interfaces
    • Generic Methods
    • Bounded type parameters
    • Applications
  • 5) Equals and Hashcode
    • Problems
  • CompareTo method overview
  • Basic DS
    • 1) Simple Array List
    • 2) Simple HashMap
  • 5) Collections Framework - Part 1
    • Introducing the collections framework
    • Working with the Collection interface
      • The core Collection interface
      • Methods of the Collection interface
    • Creating and using List, Set, and Deque implementations
      • List interface and its implementations
      • Iterators
      • Sorting List using custom sorting technique
      • Comparable Interface
      • Custom Sorting using comparator
      • ArrayList - Examples and practice problems
    • Stack
    • Linked List
    • LinkedList Operations
  • 6) Collections Framework - Part 2
    • Sets
      • Set Types
      • Array to Set (vice versa)
    • Maps
    • TreeMap
    • Autoboxing And Unboxing
  • Collections Framework - Part 3
    • Basics : DS , Number System
    • Internal Working
      • HashMap
      • HashSet
  • 7) Reflection API
  • 8) Annotations
  • 9) Reading Input From Various Sources
    • File Handling
    • Reading From Xml
    • Reading From JSON
  • 10) Multi-threading (Concurrency)
    • Protect shared data
    • Thread-safe access to shared data
  • 11) Design Patterns
    • Singleton
    • DI
  • 12) Internal Working of JVM
  • 13) Garbage Collection
  • 14) More on Strings (Buffer and Builder)
  • 15) Cloning and Immutable Class
    • 16) Serialization And Deserialization
    • Untitled
  • JAVA 8
    • Interface Changes
    • Lambda
    • Method Ref
    • Optional
    • Streams
    • Predicates
  • Practice Tests
    • Test - Collections
    • OOPS
    • S-OOPS
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  • Create top-level and nested classes :
  • Advantages of inner classes :

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3) Inner Classes

PreviousEnumsNext3.1) Static nested class (also called static inner class)

Last updated 6 years ago

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A nested class is a class defined within another class. Nested classes that are declared as static are referred to as static nested classes. Nested classes that aren’t declared as static are referred to as inner classes. Like a regular top-level class, an inner or static nested class can define variables and methods.

Create top-level and nested classes :

Advantages of inner classes :

  1. Objectify the functionality of a class, within it.For example, you might define a class Tree, which defines operations to add objects, remove objects, and sort them based on a condition. Instead of defining methods and variables to sort them within the class Tree, you could encapsulate sorting functionality within another class TreeSort. Because the class TreeSort would always work with Tree and might not be needed outside the class Tree, TreeSort can be defined as an inner class within class Tree.

  2. For using inner classes is as parameter containers.Instead of using long method signa- tures, inner classes are often used to keep method signatures compact by passing ref- erence parameters of inner classes instead of a long list of individual parameters.

An outer class showing all types of inner classes that it can define: inner class, static nested class, local inner class, and anonymous inner class