Java Basic

🔹 1. Introduction to Java

• What is Java?: A high-level, object-oriented programming language that is platform-independent, meaning Java code can run on any platform with a compatible JVM (Java Virtual Machine).

• History of Java: Created by James Gosling and Mike Sheridan at Sun Microsystems in 1991, now owned by Oracle.

• Key Features of Java:

o Platform independence (write once, run anywhere)

o Object-oriented

o Secure

o Multithreaded

o Distributed computing (supports networked applications)

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🔹 2. Java Environment Setup

• Installing JDK (Java Development Kit): Steps to install JDK and set up the Java environment on different operating systems.

• Setting up IDEs for Java:

o Eclipse: A popular IDE for Java programming.

o IntelliJ IDEA: A powerful IDE for Java with excellent features for ease of use.

o NetBeans: Another widely used IDE for Java development.

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🔹 3. Java Syntax and Structure

• Hello World Program: Writing and understanding the simplest Java program, including the basic structure:

• public class HelloWorld {

•     public static void main(String[] args) {

•         System.out.println("Hello, World!");

•     }

• }

• Java Comments:

o Single-line comments: //

o Multi-line comments: /* */

o Documentation comments: /** */

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🔹 4. Data Types and Variables

• Primitive Data Types:

o int: Integer

o float: Floating-point number

o char: Character

o double: Double precision floating-point number

o boolean: True or false values

o byte, short, long, String: Other basic data types

• Declaring Variables: Understanding variable declaration and initialization.

• int age = 25;

• boolean isStudent = true;

• String name = "John";

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🔹 5. Operators in Java

• Arithmetic Operators: +, -, *, /, %

• Relational Operators: ==, !=, <, >, <=, >=

• Logical Operators: && (AND), || (OR), ! (NOT)

• Assignment Operators: =, +=, -=, *=, /=

• Unary Operators: ++, --, +, -

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🔹 6. Control Flow Statements

• Conditional Statements:

o if-else: Used to make decisions.

o switch-case: Used for multiple possible values of a variable.

• Loops:

o for loop: Iterates over a range of values.

o while loop: Executes a block of code as long as the condition is true.

o do-while loop: Executes the code block at least once, then continues based on the condition.

• Break and Continue Statements:

o break: Exits the loop immediately.

o continue: Skips the current iteration and continues with the next one.

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🔹 7. Arrays in Java

• Array Declaration and Initialization:

o One-dimensional array:

o int[] numbers = {1, 2, 3, 4, 5};

o Two-dimensional array:

o int[][] matrix = {{1, 2}, {3, 4}, {5, 6}};

• Array Operations: Accessing, modifying, and traversing arrays using loops.

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🔹 8. Methods in Java

• Defining Methods: A method is a block of code that performs a task and can return a value.

• public static int add(int a, int b) {

•     return a + b;

• }

• Method Overloading: Having multiple methods with the same name but different parameter lists.

• Method Parameters and Return Types: Understanding how parameters and return types work in methods.

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🔹 9. Object-Oriented Programming (OOP) Concepts

• Classes and Objects:

o A class is a blueprint for creating objects (instances).

o An object is an instance of a class.

• class Car {

•     String model;

•     int year;

•

•     public void displayInfo() {

•         System.out.println("Model: " + model + ", Year: " + year);

•     }

• }

•

• public class Main {

•     public static void main(String[] args) {

•         Car myCar = new Car();

•         myCar.model = "Toyota";

•         myCar.year = 2020;

•         myCar.displayInfo();

•     }

• }

• Encapsulation: Bundling data (variables) and methods that operate on the data into a single unit (class). Using access modifiers (private, public) to control access to variables and methods.

• Inheritance: A mechanism where one class can inherit properties and methods from another class.

• class Animal {

•     void sound() {

•         System.out.println("Animal makes sound");

•     }

• }

•

• class Dog extends Animal {

•     void sound() {

•         System.out.println("Dog barks");

•     }

• }

• Polymorphism: The ability of an object to take on many forms. Method overriding and method overloading.

• Abstraction: Hiding the complex implementation details and exposing only the essential parts to the user.

• Interfaces: A contract that a class must follow by implementing the methods defined in the interface.

• interface Animal {

•     void sound();

• }

•

• class Dog implements Animal {

•     public void sound() {

•         System.out.println("Bark");

•     }

• }

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🔹 10. Exception Handling

• Try-Catch Block: Used to handle errors or exceptions in code.

• try {

•     int divideByZero = 5 / 0;

• } catch (ArithmeticException e) {

•     System.out.println("Error: " + e.getMessage());

• }

• Throw and Throws: Throwing an exception manually and declaring exceptions in method signatures.

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🔹 11. Collections Framework

• List: An ordered collection of elements (ArrayList, LinkedList).

• Set: A collection that does not allow duplicate elements (HashSet, LinkedHashSet).

• Map: A collection that stores key-value pairs (HashMap, TreeMap).

• Queue: A collection that stores elements in a FIFO (First In First Out) order.

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🔹 12. Java 8 Features

• Lambda Expressions: A concise way to represent anonymous functions.

• (a, b) -> a + b;

• Streams API: A powerful way to process sequences of elements (filter, map, reduce).

• List<String> names = Arrays.asList("John", "Jane", "Joe");

• names.stream().filter(name -> name.startsWith("J")).forEach(System.out::println);

• Default Methods in Interfaces: Methods in interfaces that have default implementations.

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🔹 13. Java File I/O

• Reading Files: Using FileReader, BufferedReader, or Scanner to read files.

• Writing to Files: Using FileWriter, BufferedWriter, or PrintWriter to write data to files.

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🔹 14. Java 9 and Later Features

• Modules (Java 9): A new way to group related packages and classes in a modular structure.

• Local-Variable Type Inference (Java 10): Using var keyword to declare variables without specifying their types.

• var name = "Java"; // Inferred as String

• Improved Pattern Matching (Java 16 and later): Simplified way to check and work with types in conditionals.

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🔹 15. Best Practices in Java Programming

• Code Readability: Consistent naming conventions, indentation, and commenting.

• Optimizing Performance: Avoiding unnecessary object creation, using efficient data structures.

• Unit Testing: Writing tests for your code using testing frameworks like JUnit.