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1. * Introduction to Java ¢ Java is a high-level, object-oriented, platform-independent programming language. ¢ Developed by James Gosling at Sun Microsystems in 1995. ¢ Famous for “Write Once, Run Anywhere” (WORA) due to JVM (Java Virtual Machine). 2. ¢ Features of Java . Simple — Easy to learn, syntax similar to C/C++. . Object-Oriented — Everything is based on objects (classes, inheritance, polymorphism). . Platform Independent = Compiles into bytecode, runs on JVM. . Secure — No pointers, has a security manager. Robust — Strong memory management, exception handling, garbage collection. . Multithreaded — Supports parallel execution. Distributed — Supports RMI (Remote Method Invocation) & networking. 4. « Basic Structure of a Java Program Java C)Copy code class HelloWorld { public static void main(String[] args) { System.out.println("Hello, World!"); } } Explanation: * class — Defines aclass. * main — Entry point. * System. out.println() = Prints output. 5. * Data Types in Java ¢ Primitive Types: © byte (1 byte), short (2), int (4), long (8) © float (4), double (8) © char (2), boolean (1) ¢ Non-Primitive Types: Strings, Arrays, Classes, Interfaces. 6. * Variables & Operators ¢ Declaration: int age = 20; ¢ Operators: o Arithmetic (+ - * / %) ° Relational (== != > < >= <=) © Logical (&& || !) o Assignment (= + *= /=) 8. * Object-Oriented Concepts 1. Class & Object © Blueprint vs Instance. 2. Encapsulation © Data hiding using private fields + getters/setters. 3. Inheritance © extends keyword — allows reuse. © Types: Single, Multilevel, Hierarchical (No multiple inheritance with classes). 4. Polymorphism © Compile-time (method overloading). © Runtime (method overriding). 5. Abstraction o Abstract class (abstract) or Interface (interface). 9. ¢ Important Concepts ¢ Constructors: Special method to initialize objects. ¢ this & super: Used to refer current class / parent class. ¢ static keyword: Belongs to class, not object. ¢ final keyword: Used with variables, methods, classes. ¢ Packages: Collection of classes (import java.util.*;). 11. ¢ Multithreading ¢ Java supports concurrency with Thread class & Runnable interface. Java () Copy code class MyThread extends Thread { public void runc) { System.out.println¢"Thread running..."); } } public class Test { public static void main(String[] args) { MyThread t = new MyThread(¢); t.start(); 12. « Java Collections Framework ¢ Interfaces: List, Set, Map, Queue. ¢ Implementations: © ArrayList, LinkedList ° HashSet, TreeSet © HashMap, TreeMap 14. * Advanced Topics ¢ File Handling (File, FileReader, BufferedReader). * Networking (Sockets, RMI). ¢ JDBC (Java Database Connectivity). ¢ JavaFX / Swing (GUI programming). ¢ Lambda Expressions & Streams (Java 8+). 15. « Commonly Used Java Tools * Eclipse / IntelliJ IDEA — IDEs. * Maven / Gradle — Build tools. * JUnit — Testing framework. 
