Java

Basic Concepts

Variables and Data Types

• Primitive types: int, float, double, char, boolean, byte, short, long

• Non-primitive types: String, Arrays, Classes, Interfaces

Operators

• Arithmetic: +, -, *, /, %

• Relational: ==, !=, >, <, >=, <=

• Logical: &&, ||, !

• Assignment: =, +=, -=, etc.

• Unary: ++, --

Control Statements

• Conditional statements: if, if-else, switch

• Loops: for, while, do-while

• Branching: break, continue, return

Methods / Functions

• Defining methods: return type, parameters

• Method overloading

• Recursion

• main() method

Object-Oriented Programming (OOP) Basics

• Classes & Objects

• Fields (attributes) and Methods

• Constructors

• this keyword

• Inheritance (extends)

• Polymorphism (overloading & overriding)

• Abstraction (abstract classes, interface)

• Encapsulation (getters/setters)

• Access modifiers: public, private, protected, default

Arrays

• Single-dimensional arrays

• Multi-dimensional arrays

• Array initialization and traversal

Strings

• String class

• String methods (length(), charAt(), substring(), equals(), concat())

• StringBuilder & StringBuffer

Exception Handling

• try-catch-finally

• throw and throws

• Common exceptions: NullPointerException, ArrayIndexOutOfBoundsException, etc.

Packages and Import

• java.lang, java.util, etc.

• Creating custom packages

• import statement

Basic Input/Output

• Scanner class

• System.out.print / println

• File I/O basics (File, FileReader, FileWriter)

Basic Keywords

• static, final, void, new, super, this, class, interface, abstract, extends, implements