Lecture Notes: Collection Framework in Java

Overview

• Collection vs Collection Framework
  • Collection: Represents a group of objects as a single entity.
  • Collection Framework: Includes multiple interfaces and classes.

Key Concepts

• Collection Interface
  • Root interface for all collection-related classes and interfaces.
  • Provides common methods (e.g., adding, removing, checking objects) used across collections.

Main Interfaces in Collection Framework

1. Collection Interface

• Root interface with common methods for all collections.
• Methods are used to represent and manipulate group of objects.

2. Collections Class

• Part of java.util package.
• Provides utility methods for collection objects.
• Example: Collections.sort() to sort elements in a collection like ArrayList.

Child Interfaces of Collection

List Interface

• Child of Collection Interface.
• **Characteristics: **
  • Preserves insertion order.
  • Allows duplicates.
• **Implementing Classes: **
  • ArrayList
  • LinkedList
  • Vector
  • Stack

Set Interface

• Child of Collection Interface.
• **Characteristics: **
  • Does not preserve insertion order.
  • Does not allow duplicates.
• **Implementing Classes: **
  • HashSet
  • LinkedHashSet

Queue Interface

• Child of Collection Interface.
• **Characteristics: **
  • First In First Out (FIFO) behavior.
  • Used for processing objects in a queue.
• **Implementing Class: **
  • PriorityQueue

Map Interface

• Separate from Collection Interface.
• **Characteristics: **
  • Stores elements in key-value pairs.
  • Keys are unique, values can be duplicated.
• **Implementing Classes: **
  • HashMap
  • LinkedHashMap

Summary

• List Interface: Use when insertion order is important and duplicates are needed.
• Set Interface: Use when no duplicates are required and insertion order does not matter.
• Queue Interface: Use for processing items in FIFO order.
• Map Interface: Use to store key-value pairs, allowing unique keys.