Java Collections Framework

Java Collections

Overview

• A collection of classes and interfaces that implement commonly used data structures such as lists, sets, and maps
• Part of the Java Standard Library, java.util package

Key Interfaces

• Collection: root interface for all collections, provides basic operations (add, remove, contains, etc.)
• List: ordered collection, allows duplicates (e.g., ArrayList, LinkedList)
• Set: unordered collection, no duplicates (e.g., HashSet, LinkedHashSet)
• Map: key-value pairs, no duplicates (e.g., HashMap, LinkedHashMap)

Key Classes

• ArrayList: resizable array implementation of List
• LinkedList: doubly-linked list implementation of List
• HashSet: implementation of Set using a hash table
• HashMap: implementation of Map using a hash table

Operations

• add(), remove(), contains(), size(), iterator()

OOPs Concepts

Classes and Objects

• Class: blueprint for creating objects, defines properties and behaviors
• Object: instance of a class, has its own state and behavior

Inheritance

• Single Inheritance: a class can extend one parent class
• Multilevel Inheritance: a class can extend a class that itself extends another class
• Hierarchical Inheritance: multiple classes can extend a single parent class
• Multiple Inheritance: not directly supported in Java, but can be achieved using interfaces

Polymorphism

• Method Overloading: multiple methods with same name but different parameters
• Method Overriding: a subclass provides a specific implementation of a method already defined in its superclass

Abstraction and Encapsulation

• Abstraction: showing only necessary information to the outside world
• Encapsulation: hiding implementation details and exposing only necessary information through public methods

Java Syntax

Variables and Data Types

• Primitive Data Types: byte, short, int, long, float, double, boolean, char
• Reference Data Types: classes, interfaces, arrays
• Variable Declaration: type variableName [= initialValue];

Operators

• Arithmetic Operators: +, -, *, /, %
• Comparison Operators: ==, !=, <, >, <=, >=
• Logical Operators: &&, ||, !
• Assignment Operators: =, +=, -=, *=, /=, %=, etc.

Control Flow Statements

• If-Else Statements: if (condition) { code } else { code }
• Switch Statements: switch (expression) { case value: code; break; ... }
• Loops: while (condition) { code }, for (init; condition; increment) { code }, do { code } while (condition);

Methods

• Method Declaration: returnType methodName(parameters) { code }
• Method Invocation: methodName(arguments)

Java Collections

Overview

• Java Collections is a collection of classes and interfaces that implement commonly used data structures
• It is part of the Java Standard Library, found in the java.util package

Key Interfaces

• Collection: provides basic operations like add, remove, contains, etc. and is the root interface for all collections
• List: an ordered collection that allows duplicates
• Set: an unordered collection that does not allow duplicates
• Map: a collection of key-value pairs that does not allow duplicates

Key Classes

• ArrayList: a resizable array implementation of List
• LinkedList: a doubly-linked list implementation of List
• HashSet: an implementation of Set using a hash table
• HashMap: an implementation of Map using a hash table

Operations

• add(): adds an element to a collection
• remove(): removes an element from a collection
• contains(): checks if a collection contains an element
• size(): returns the number of elements in a collection
• iterator(): returns an iterator over the elements in a collection

OOPs Concepts

Classes and Objects

• A class is a blueprint for creating objects and defines properties and behaviors
• An object is an instance of a class and has its own state and behavior

Inheritance

• Single Inheritance: a class can extend one parent class
• Multilevel Inheritance: a class can extend a class that itself extends another class
• Hierarchical Inheritance: multiple classes can extend a single parent class
• Multiple Inheritance: not directly supported in Java, but can be achieved using interfaces

Polymorphism

• Method Overloading: multiple methods with the same name but different parameters
• Method Overriding: a subclass provides a specific implementation of a method already defined in its superclass

Abstraction and Encapsulation

• Abstraction: showing only necessary information to the outside world
• Encapsulation: hiding implementation details and exposing only necessary information through public methods

Java Syntax

Variables and Data Types

• Primitive Data Types: byte, short, int, long, float, double, boolean, char
• Reference Data Types: classes, interfaces, arrays
• Variables are declared using the syntax type variableName [= initialValue];

Operators

• Arithmetic Operators: +, -, *, /, %
• Comparison Operators: ==, !=, >, <
• Logical Operators: &&, ||, !
• Assignment Operators: =, +=, -=, *=, /=, %=, etc.

Control Flow Statements

• If-Else Statements: used for conditional execution of code
• Switch Statements: used for conditional execution of code based on the value of an expression
• Loops: used for repeated execution of code, including while, for, and do-while loops

Methods

• Method Declaration: methods are declared using the syntax returnType methodName(parameters) { code }
• Method Invocation: methods are invoked using the syntax methodName(arguments)

This quiz covers the Java Collections Framework, a part of the Java Standard Library, and its key interfaces such as Collection, List, and Set.