Java Programming Study Notes

Abstract Classes in Java

Understand Java abstract classes, how they mix abstract and concrete methods, and when to choose them over interfaces.

Abstraction in Java

Understand abstraction in Java through abstract classes and interfaces, and how they hide implementation details from the user.

ArrayList in Java

Learn how ArrayList works internally, its time complexity, and when to use it over arrays or LinkedList.

Arrays in Java

Learn how Java arrays store fixed-size, homogeneous collections of elements on the heap, including declaration, default values, and common runtime errors.

break and continue in Java

Understand how break and continue alter loop execution in Java, including labeled break/continue for controlling nested loops directly.

Checked vs Unchecked Exceptions in Java

Compare checked and unchecked exceptions in Java, including compiler enforcement, typical use cases, and common exam pitfalls.

Classes and Objects in Java

Learn how classes act as blueprints and objects as instances in Java, with syntax, examples, and exam-focused explanations.

Collections Framework in Java

Understand the Java Collections Framework hierarchy — Collection vs Map, List/Set/Queue interfaces, and how to pick the right implementation.

Comments in Java

Learn the three types of comments in Java — single-line, multi-line, and Javadoc — and best practices for using them.

Constants (final keyword) in Java

Learn how to declare constants in Java using the final keyword, and understand its use with variables, methods, and classes.

Constructors in Java

Understand Java constructors — default, parameterized, overloaded, and chained — with syntax rules and worked examples.

Custom Exceptions in Java

Learn how to define and throw your own checked or unchecked exception classes in Java for clearer, domain-specific error handling.

Data Types in Java

A complete guide to Java's 8 primitive data types with exact sizes and ranges, plus reference types like String and arrays.

Encapsulation in Java

Learn how encapsulation in Java bundles data and behavior together using private fields, access modifiers, and getters/setters.

Exceptions in Java

Understand what exceptions are in Java, how the Throwable hierarchy is organized, and why exception handling keeps programs robust.

Features of Java

Explore the core features that make Java popular — object-oriented design, platform independence, robustness, security, multithreading, and high performance vi…

finally Block in Java

Learn how the finally block guarantees cleanup code execution in Java, even when exceptions or return statements are involved.

for Loop in Java

Understand Java's classic three-part for loop and the enhanced for-each loop for iterating over arrays and collections concisely.

Generics in Java

Understand how Java generics provide compile-time type safety with type parameters, bounded types, wildcards, and the concept of type erasure.

HashMap in Java

Learn how HashMap stores key-value pairs using hashing, its null-key rules, and why iteration order is not guaranteed.

HashSet in Java

Understand how HashSet guarantees uniqueness by wrapping a HashMap internally, with average O(1) add/contains/remove.

History and Evolution of Java

Trace Java's origins from Sun Microsystems' 'Oak' project through its 1995 public release to its current ownership by Oracle, and understand key milestones in…

if-else in Java

Learn how Java's if-else statement controls program flow with conditional branching, including if, if-else, else-if ladders, and nested if statements.

Inheritance in Java

Understand Java inheritance using the extends keyword, the super keyword, single inheritance rules, and the Object root class.