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Chapter 4: Variables, Data Types, and Operators in Java Chapter 4: Variables, Data Types, and Operators in Java In this chapter, we’ll dive into the foundational elements of Java: variables , data types , and operators . Understanding these concepts is essential to start writing functional Java programs. 1. Java Variables Variables are containers for storing data values. In Java, you must declare a variable before you use it. int age = 25; String name = "John"; Here, int and String are data types, while age and name are variable names. Types of Variables Local Variable – Declared inside a method. Instance Variable – Declared inside a class but outside any method. Static Variable – Declared with the static keyword. 2. Java Data Types Java is a statically typed language, meaning all variables must be declared with a data type. Primitive Data Types byte – 1 byte, range: -128 to 127 ...

Chapter 10: File Handling in Java | Read, Write, Create Files 📁 Chapter 10: File Handling in Java File handling in Java is essential when dealing with data storage and retrieval in the form of text or binary files. Java offers various classes and methods in the java.io and java.nio packages to handle files. 🔹 Why File Handling is Important? To store data persistently To read configuration or input data from external files To generate logs and reports To handle user uploads/downloads 📦 Java File Handling Classes File – Represents a file or directory FileWriter – For writing text to files FileReader – For reading text files BufferedReader – Reads text efficiently, line by line BufferedWriter – Writes text efficiently Scanner – Reads file content easily with parsing capabilities 📂 1. Creating a File import java.io.File; import java.io.IOException; public class CreateFil...

Chapter 9: Exception Handling in Java Chapter 9: Exception Handling in Java In Java, exception handling is a powerful mechanism to handle runtime errors, allowing the normal flow of the program to continue. Without proper exception handling, errors can lead to unexpected termination of the program. 📌 What is an Exception? An exception is an event that disrupts the normal flow of a program’s execution. It is an object which is thrown at runtime. Common Exception Types: ArithmeticException – Divide by zero NullPointerException – Accessing object with null reference ArrayIndexOutOfBoundsException – Invalid index access NumberFormatException – Invalid number parsing 🧪 Java Exception Hierarchy All exceptions are subclasses of Throwable : Throwable Error Exception RuntimeException 🔧 Java Exception Handling Keyword...

Chapter 12: Multithreading in Java Chapter 12: Multithreading in Java Multithreading is one of Java's powerful features, allowing concurrent execution of two or more parts of a program for maximum utilization of CPU. Each part of such a program is called a thread . 🔄 1. What is a Thread? A thread is a lightweight process. It's a path of execution within a program. Java supports multithreaded programming using built-in Thread class and Runnable interface. 🛠️ 2. Creating Threads in Java Method 1: By extending Thread class class MyThread extends Thread { public void run() { System.out.println("Thread is running..."); } } public class TestThread { public static void main(String args[]) { MyThread t1 = new MyThread(); t1.start(); } } Method 2: By implementing Runnable interface class MyRunnable implements Runnable { public void run() { ...

Chapter 11: Java Collections Framework Chapter 11: Java Collections Framework 🔰 Introduction The Java Collections Framework (JCF) is a set of classes and interfaces that implement commonly reusable collection data structures. It provides algorithms and utilities to manage groups of objects effectively. 🌲 Core Interfaces in Collections Collection: Root interface of the collection hierarchy. List: An ordered collection that allows duplicate elements (e.g., ArrayList, LinkedList). Set: A collection that does not allow duplicate elements (e.g., HashSet, TreeSet). Map: Stores key-value pairs (e.g., HashMap, TreeMap). Queue: Designed for holding elements prior to processing (e.g., LinkedList, PriorityQueue). 🔄 List Interface Ordered, allows duplicate elements. Access by index. List<String> names = new ArrayList<>(); names.add("Alice"); names.add("Bob"); 🧱 Set Interfac...

Chapter 6: Arrays and Strings in Java Chapter 6: Arrays and Strings in Java Welcome to Chapter 6 of our Java Programming Course! In this chapter, we'll explore two of the most fundamental data structures in Java: Arrays and Strings . 🔹 What is an Array in Java? An Array is a collection of elements, all of the same type, stored in contiguous memory locations. It allows you to store multiple values in a single variable. 👉 Declaration and Initialization int[] numbers = new int[5]; // Declaration numbers[0] = 10; numbers[1] = 20; // ... up to index 4 👉 Shortcut Initialization int[] numbers = {10, 20, 30, 40, 50}; 👉 Accessing Array Elements System.out.println(numbers[2]); // Output: 30 👉 Array Length System.out.println("Length: " + numbers.length); 🔹 Multidimensional Arrays int[][] matrix = { {1, 2, 3}, {4, 5, 6} }; 🔹 Looping Through Arrays for (int i = 0; i < numbers.length; i++) { System.out.println(numbers[i]); ...

Chapter 1: Introduction to Java 1.1 What is Java? Java is a high-level, object-oriented, platform-independent programming language developed by Sun Microsystems (now owned by Oracle). It is used to build web, mobile, desktop, and enterprise applications. It follows the WORA principle — Write Once, Run Anywhere — allowing compiled code to run on any device with the JVM (Java Virtual Machine). 1.2 History of Java Java was created by James Gosling and his team at Sun Microsystems in 1995. Originally named Oak, it was designed for interactive television, but later rebranded as Java and optimized for web applications. 1.3 Features of Java Simple: Easy to learn and use, especially for those familiar with C/C++. Object-Oriented: Promotes modularity, code reuse, and better structure. Platform-Independent: Runs on any OS with JVM. Secure: Uses sandboxing and classloaders to prevent malicious code. Robust: Strong memory management, garbage collect...

  Chapter 3: Java Syntax and Basic Structure 3.1 Structure of a Java Program A basic Java program follows a specific structure that includes: Class definition main() method (entry point) Statements inside curly braces Example: Public class MyProgram { public static void main(String[] args) { System.out.println("Java is powerful!"); } } 3.2 Components of a Java Program 3.3 Java Syntax Rules Java is case-sensitive: Main ≠ main File name must match the class name (for public class) The main() method must be exactly: public static void main(String[] args) 3.4 Java Comments Comments are used to make code easier to understand. Single-line comment: // This is a single-line comment Multi-line comment: /* This is a multi-line comment */ Documentation comment (for APIs): /** * This class prints Hello World. */ 3.5 Printing Output in Java We use System.out.println() or System.out.print() to show output. ➤ Example: System.out.println("Welcome!"); System.out.print("Hello ...