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Java Classes in Depth – Complete Guide with Definitions, Syntax & Examples Java Classes in Depth – Complete Guide with Definitions, Syntax & Examples Explore various types of Java Classes with clear explanations, real-world examples, and easy-to-follow syntax. 📚 Related Java Class Topics 1. Concrete Class in Java – Definition 2. Anonymous Class in Java – Definition 3. Inner Class in Java – Definition & Syntax 4. Singleton Class in Java – Definition 5. Static Nested Class in Java – Definition 6. POJO Class in Java – Definition & Syntax 7. Final Class in Java – Definition & Syntax 8. Abstract Class in Java – Definition, Syntax & Example Learn Java Free – Complete 14-Chapter Course © 2025 Java Learning Hub | Designed by OP Verma

2. Abstract Class in Java In Java, an abstract class cannot be instantiated and is meant to be extended by other classes. It provides a common base and allows some methods to be abstract, so subclasses implement them. Can have abstract methods (no body) Can have concrete methods (with body) Can have constructors, fields, and static methods Can implement interfaces Declared with the abstract keyword Key Points Classes with abstract methods must be declared abstract Abstract methods end with a semicolon, no body Subclasses must override abstract methods or be abstract Abstract classes can have constructors Syntax abstract class ClassName { abstract void display(); // abstract method void show() { // concrete method System.out.println("Concrete method"); } } Example abstract class Animal { abstract void sound(); void sleep() { System.out.println("Sleeping..."); } } class ...

Singleton Class in Java – Definition, Syntax, and Example Singleton Class in Java – Definition, Syntax, and Example Definition: A Singleton Class in Java is a design pattern that ensures only one instance of the class exists in the JVM. It provides a global point of access to that instance. Key Points: Only one instance is created during the entire lifecycle. Private constructor to prevent external instantiation. Static method to provide access to the single instance. Syntax Example: public class Singleton { private static Singleton instance; private Singleton() { // private constructor } public static Singleton getInstance() { if (instance == null) { instance = new Singleton(); } return instance; } } public class Main { public static void main(String[] args) { Singleton obj1 = Singleton.getInstance(); Singleton obj2 = Singleton.getInstance(); System.out....

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...