*A–Z of Java programming concepts* 👨‍💻☕ *A – Abstraction* Hiding implementation details and showing only the essential features. ```java abstract class Animal { abstract void makeSound(); } ``` *B – Bytecode* Intermediate code generated after compiling `.java` files, executed by the JVM. *C – Class* Blueprint for creating objects with fields and methods. ```java class Car { String model; void drive() {...} } ``` *D – Data Types* Java has primitive (int, float, etc.) and reference (arrays, objects) types. *E – Encapsulation* Wrapping data and methods into a single unit and restricting access via modifiers. ```java class Person { private String name; public String getName() { return name;} } ``` *F – Final Keyword* Used to declare constants, prevent inheritance, or method overriding. *G – Garbage Collection* Automatic memory management that clears unused objects. *H – HashMap* Key-value pair collection with fast retrieval. ```java Map map = new HashMap<>(); ``` *I – Interface* A contract that classes implement. Supports multiple inheritance. ```java interface Flyable { void fly();} ``` *J – JVM (Java Virtual Machine)* Runs Java bytecode and provides platform independence. *K – Keywords* Reserved words like `class`, `static`, `public`, `if`, `while`, etc. (Java has 50+). *L – Lambda Expressions* Short syntax for functional interfaces (Java 8+). ```java (e) -> System.out.println(e) ``` *M – Method Overloading* Defining multiple methods with the same name but different parameters. *N – NullPointerException* Common runtime error when accessing a null reference. *O – Object-Oriented Programming (OOP)* Java is based on OOP principles: encapsulation, inheritance, abstraction, polymorphism. *P – Polymorphism* Same method behaves differently depending on the object/class context. ```java Animal a = new Dog(); a.makeSound(); // behaves like Dog ``` *Q – Queue* FIFO data structure implemented with interfaces like `Queue` or `Deque`. ```java Queue q = new LinkedList<>(); ``` *R – Recursion* A method calling itself for problem-solving. ```java int factorial(int n) { return (n <= 1)? 1: n * factorial(n - 1); } ``` *S – Static Keyword* Used for methods and variables that belong to the class rather than instances. *T – Try-Catch Block* Used to handle exceptions in Java. ```java try {...} catch (Exception e) {...} ``` *U – Unary Operators* Operators with only one operand, like `++`, `--`, `!`. *V – Variable Scope* Defines where variables can be accessed: local, instance, or static. *W – Wrapper Classes* Convert primitive types into objects: `Integer`, `Double`, etc. *X – XML Parsing* Java supports parsing XML using libraries like JAXB, DOM, or SAX. *Y – YAML & JSON Handling* Java can handle external formats like YAML/JSON with libraries like Jackson or SnakeYAML. *Z – Zero-based Indexing* Like many languages, Java arrays/lists start indexing from zero. 💬 *React with ❤️ for more* ✨