Category Concept Description Example Basics Hello World Basic program to print "Hello, World!" java public class HelloWorld {   public static void main(String[] args) {   System.out.println("Hello, World!");   } } Data Types Primitive types: int , double , char , boolean , etc., and reference types java int a = 10; double b = 5.5; char c = 'A'; boolean isTrue = true; String name = "Alice"; Variables Storage locations with type and name java int age = 25; double salary = 50000.0; String employee = "John Doe"; Operators Arithmetic, Relational, Logical, Bitwise, Assignment operators java int sum = a + b; if (a > b && b < c) {   // ... } Control Flow If-Else Conditio...