Course Overview

This course teaches Java from the ground up — starting with how the JVM works and your first program, through to OOP, Collections, and Exception Handling. Every concept is reinforced with hands-on coding. By the end you will be fluent in core Java and fully prepared for technical interviews in software development and QA automation roles.

Core Java OOP — 4 Pillars Collections Framework String & StringBuilder Exception Handling Interview Coding Problems

🚀 Course Progression

Each module builds on the previous — from first program to production-ready Java skills.

1Syntax & Logic
2OOP Concepts
3Collections & Strings
4Crack the Interview
🏆Hired!
MODULE 01

 Introduction to Java & Setup

💡 You write and run your first Java program and understand exactly how the language works under the hood — the foundation every other module builds on.
Java Environment & Architecture
  • JDK vs JRE vs JVM — what each component does and why all three matter
  • How Java achieves platform independence — write once, run anywhere via bytecode
  • Installing JDK and setting up Eclipse IDE for Java development
  • Configuring JAVA_HOME and verifying with java -version
First Java Program
  • Structure of a Java class — class keyword, public static void main(String[] args)
  • System.out.println() and System.out.print() — printing output to the console
  • Compiling with javac and running with java from the command line
  • Organising classes into packages — naming conventions and folder structure
MODULE 02

 Data Types & Variables

💡 Every Java program stores and processes data. Understanding exactly which data type to use — and how Java converts between them — prevents bugs and writes cleaner code.
Primitive Data Types
  • Variable declaration and assignment — naming rules and conventions
  • Integer types: byte, short, int, long — size and valid range of each
  • Floating-point types: float vs double — precision and when to use each
  • char — single Unicode character, stored as a 16-bit number
  • boolean — true / false only; used in all conditions and loops
  • String — non-primitive reference type; immutable character sequence
Type Conversion & Constants
  • final keyword — declaring a constant that cannot be reassigned
  • Widening (implicit) conversion — Java automatically promotes smaller types to larger
  • Narrowing (explicit) casting — (int) 3.14 — data loss risk and when it is acceptable
MODULE 03

 Operators

💡 Operators are the verbs of Java — without them, no calculation, comparison, or logical decision is possible. Every program you write will use them constantly.
Operator Types
  • Arithmetic: +, -, *, /, % (modulus) — integer division behaviour
  • Increment / Decrement: ++, -- — prefix vs postfix difference
  • Relational: ==, !=, >, <, >=, <= — always return boolean
  • Logical: && (AND), || (OR), ! (NOT) — short-circuit evaluation
  • Assignment shortcuts: +=, -=, *=, /=, %=
  • Ternary operator: condition ? valueIfTrue : valueIfFalse
MODULE 04

 Control Flow — Conditional Statements

💡 Real programs don't run the same code every time — they make decisions. Control flow is what makes a program respond differently depending on input or state.
Conditional Statements
  • if, else, else if ladder — single and multi-branch decision making
  • Nested if — conditions inside conditions for complex logic
  • switch statement — case, default, and break; fall-through behaviour
  • Scanner class — nextInt(), nextLine(), nextDouble() for reading user input
MODULE 05

 Loops & Pattern Printing

💡 Loops eliminate repetition from code and are behind every list, table, and bulk operation in real applications. Pattern printing sharpens your loop logic for interviews.
Loop Types & Control Statements
  • for loop — initialisation, condition, update; most common for counted iterations
  • while loop — condition checked before each iteration; runs zero or more times
  • do-while loop — condition checked after; always executes at least once
  • break — immediately exits the current loop
  • continue — skips the rest of the current iteration and moves to the next
  • Nested loops — outer loop controls rows, inner loop controls columns
Pattern Printing
  • Star (*) patterns — right triangle, left triangle, pyramid, diamond
  • Number patterns — sequential, mirrored, and Pascal's triangle style
  • Analysing patterns — how to break any design into row count and column logic
MODULE 06

 Arrays — 1D & 2D

💡 Arrays are the simplest way to store multiple values under one name. They appear in almost every coding interview question and are the foundation of all other data structures.
1D Arrays
  • Array declaration: int[] arr = new int[5] — fixed size, zero-indexed
  • Initialisation at declaration: int[] arr = {10, 20, 30}
  • arr.length — getting the size of an array
  • Iterating with for loop and enhanced for-each loop
  • Common operations: finding max/min, sum, average, reverse, search
  • Arrays.sort() — sorting in ascending order
2D Arrays
  • Declaration: int[][] matrix = new int[rows][cols] — row-major storage
  • Nested loops to traverse rows and columns of a 2D array
  • Matrix operations — addition, transpose, diagonal sum
MODULE 07

 Methods

💡 Methods let you write a block of code once and reuse it anywhere. Without methods, every program becomes one giant, unreadable block — methods are the first step toward professional code organisation.
Defining & Using Methods
  • Method signature: access modifier, return type, method name, parameter list
  • Calling a method — passing arguments, receiving return values
  • void methods vs methods with a return type
  • static methods — called on the class directly without creating an object
  • Instance (non-static) methods — require an object to call
  • Method overloading — same name, different parameter types or count
  • Writing generic, reusable utility methods for common operations
MODULE 08

 OOP — Classes, Objects & Constructors

💡 OOP is how the entire software industry organises code at scale. Classes and objects are the building blocks — once you understand them, you can read and work with any professional Java codebase.
Classes & Objects
  • Class as a blueprint — instance variables (fields) and instance methods
  • Creating objects: ClassName obj = new ClassName()
  • Default constructor — auto-provided by Java when no constructor is defined
  • Parameterised constructor — initialising objects with values at creation time
  • this keyword — resolving naming conflicts between parameters and instance fields
static & final Members
  • static variable — one copy shared across all instances of a class
  • static method — belongs to the class, not to any object
  • final variable — constant; must be assigned exactly once
  • final method — cannot be overridden by a subclass
  • final class — cannot be extended (e.g. String is a final class)
MODULE 09

 OOP — Inheritance & Encapsulation

💡 Inheritance lets you reuse and extend existing code without rewriting it. Encapsulation protects your data from being changed incorrectly — both are used in every professional Java project.
Inheritance
  • extends keyword — child class inherits all non-private members of the parent
  • super keyword — calling the parent class constructor or methods
  • Types: single inheritance, multilevel inheritance, hierarchical inheritance
  • Java does not support multiple class inheritance — why, and how interfaces solve this
Encapsulation & Access Modifiers
  • private, protected, public, package-private — scope of each
  • Encapsulation pattern — private fields with public getter and setter methods
  • Why encapsulation prevents invalid state and makes code easier to maintain
  • Method overloading — same method name, different parameter signature
MODULE 10

 OOP — Polymorphism & Type Casting

💡 Polymorphism lets one interface work with many types — it's what makes frameworks and libraries extensible. Understanding it is essential for both interviews and reading real-world code.
Method Overriding & Runtime Polymorphism
  • Method overriding — child class provides its own implementation of a parent method
  • @Override annotation — compile-time check that overriding is valid
  • Runtime (dynamic) polymorphism — method resolved at runtime based on actual object type
  • Overloading vs overriding — compile-time vs runtime; key differences interviewers test
Object Type Casting
  • Upcasting — implicit; Animal a = new Dog() — always safe
  • Downcasting — explicit; Dog d = (Dog) a — requires instanceof check
  • instanceof operator — safely checking type before casting
MODULE 11

 Interfaces & Abstract Classes

💡 Interfaces and abstract classes are the tools Java uses to enforce contracts and structure large systems. The "Interface vs Abstract Class" question appears in nearly every Java interview.
Interfaces
  • interface keyword — defines a contract of method signatures without implementation
  • implements keyword — a class agrees to provide all interface methods
  • Interface methods are implicitly public abstract; fields are public static final
  • A class can implement multiple interfaces — Java's answer to multiple inheritance
Abstract Classes
  • abstract class — cannot be instantiated; must be subclassed
  • abstract method — declared without a body; subclass must provide implementation
  • Can contain both abstract methods and fully implemented (concrete) methods
  • Interface vs abstract class — when to use each; key differences for interviews
MODULE 12

 String Handling

💡 Strings are the most commonly used data type in real applications. Java's String methods cover the majority of text-related interview questions — mastering them is essential.
String Class & Key Methods
  • String is immutable — every operation creates a new object in the String Pool
  • length(), charAt(int), indexOf(String), lastIndexOf()
  • substring(int start), substring(int start, int end)
  • toUpperCase(), toLowerCase(), trim()
  • replace(), contains(), startsWith(), endsWith()
  • equals() vs equalsIgnoreCase() vs == — why == compares references, not content
  • split(String regex), join(), toCharArray()
StringBuilder & StringBuffer
  • StringBuilder — mutable, not thread-safe, faster for single-threaded use
  • append(), insert(), delete(), reverse(), toString()
  • StringBuffer — mutable, thread-safe, used in multi-threaded programs
  • String vs StringBuilder vs StringBuffer — performance and thread-safety trade-offs
MODULE 13

 Collections Framework

💡 The Collections Framework gives you powerful, ready-made data structures used in every Java application. Knowing which one to choose — and why — is one of the most tested topics in Java interviews.
List — Ordered, Allows Duplicates
  • ArrayList — dynamic array; fast random access; allows duplicates; maintains insertion order
  • LinkedList — doubly-linked list; fast add/remove at ends; slower random access
  • Common methods: add(), get(int), remove(), size(), contains(), set()
  • Iterating with for-each and Iterator
Set — No Duplicates
  • HashSet — no duplicates, no guaranteed order; backed by a hash table
  • LinkedHashSet — no duplicates, preserves insertion order
  • TreeSet — no duplicates, elements stored in natural sorted order
Queue & Stack
  • Queue interface — FIFO; offer(), poll(), peek()
  • Stack — LIFO; push(), pop(), peek()
  • Vector — legacy thread-safe version of ArrayList
Map — Key-Value Pairs
  • HashMap — key-value pairs, no guaranteed order, allows one null key
  • LinkedHashMap — key-value pairs, preserves insertion order
  • Common methods: put(), get(), remove(), containsKey(), keySet(), values()
Sorting & Iteration
  • Comparable interface — compareTo() for natural ordering inside the class
  • Comparator interface — compare() for custom ordering defined outside the class
  • Collections.sort(list) and Collections.sort(list, comparator)
  • Iterator — hasNext() and next() for safe manual traversal
MODULE 14

 Exception Handling

💡 Real programs encounter unexpected errors — bad user input, missing files, network failures. Exception handling is how Java programs recover gracefully instead of crashing.
Exception Handling Mechanism
  • What is an exception — an unexpected event that disrupts normal program execution
  • Checked vs unchecked exceptions — compile-time vs runtime
  • try block — code that may throw an exception
  • catch(ExceptionType e) — handling a specific exception type
  • Multiple catch blocks — handling different exception types separately
  • finally block — always executes; used for resource cleanup (closing files, connections)
  • throw keyword — manually throwing an exception from your code
  • throws keyword — declaring that a method may throw a checked exception
  • Common exceptions: NullPointerException, ArrayIndexOutOfBoundsException, NumberFormatException, ArithmeticException
BONUS

 Interview Preparation

💡 Technical knowledge alone is not enough — interviews test how clearly you can explain and apply it. This section prepares you for exactly what gets asked.
Most-Asked Java Interview Topics

OOP Pillars — Be ready to explain all four: Inheritance, Polymorphism, Encapsulation, Abstraction — with examples and real code. Overloading vs overriding is always asked.

Collections Comparison — Know ArrayList vs LinkedList, HashMap vs LinkedHashMap, HashSet vs TreeSet, and when to use Comparable vs Comparator.

String Questions — Why is String immutable? What is the String Pool? When to use StringBuilder? How does equals() differ from ==? These are asked in virtually every interview.

Interface vs Abstract Class — One of the most common Java questions. Know the differences clearly: multiple implementation, constructors, default methods, and when each design choice makes sense.

Exception Handling — Always demonstrate correct try-catch-finally usage. Know the difference between checked and unchecked exceptions and when to use throw vs throws.

Coding Rounds — Practice array problems, string manipulation, pattern printing, and number challenges on LeetCode or HackerRank. Write clean, well-named code — interviewers notice.