Java Core & Fundamentals Tutorial
Java tutorial for beginners on Java 25. Install the JDK, run a first program and follow a 12-step learning path plus an index of every Java topic.
Object-Oriented Programming (OOP) is a programming paradigm that is based on the concept of “objects.” In Java, OOP is a fundamental programming approach, and the language itself is designed to be object-oriented.
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Sealed Classes and Interfaces in Java (with Examples)
Learn sealed classes and interfaces in Java with permits, final, sealed and non-sealed subclasses, records, exhaustive switch and the reflection API.
Java Instance Initializer Block: Order, Rules and Examples
Instance initializer block in Java with examples, covering execution order with fields and constructors, this() chaining, exceptions and double braces.
extends vs implements in Java: Differences With Examples
Learn extends vs implements in Java with examples, a comparison table, using both in one class, interfaces extending interfaces, generics bounds and FAQs.
Java instanceof Operator and Pattern Matching Explained
The Java instanceof operator checks the type of an object. Learn null handling, pattern matching, generics, arrays, switch patterns and isInstance().
Private Methods in Interfaces in Java (with Examples)
Private methods in interfaces let default and static methods share code without exposing it. Learn the rules, the compile errors and a real example.
Java Constructors: Default, Parameterized, Chaining, Records
Java constructor types with examples. Default vs no-arg, parameterized, this() and super() chaining, Java 25 flexible constructor bodies and records.
Java Inheritance: extends, super, Types and Examples
Java inheritance explained with extends and super, what a subclass inherits, types of inheritance, final and sealed classes, and composition.
Association, Aggregation and Composition in Java (with UML)
Association, aggregation and composition in Java with UML notation, code that enforces ownership, a comparison table, JPA cascade mapping and FAQs.
Java OOP Concepts: The 4 Pillars with Examples
Java OOP concepts explained with runnable Java 25 examples of abstraction, encapsulation, inheritance and polymorphism, plus records and sealed types.
Multiple Inheritance in Java: Interfaces and the Diamond Problem
Multiple inheritance in Java with interfaces and default methods, the three rules that resolve the diamond problem, and composition as an option.
Java Access Modifiers Explained With Examples and Modules
Java access modifiers with examples and a table. Learn private, package-private, protected and public, the protected trap, overriding rules and modules.
Method Overloading vs Overriding in Java: Rules and Examples
Method overloading vs overriding in Java with rules, overload resolution, @Override, covariant returns and the traps that come up in interviews.
Polymorphism in Java: Overloading, Overriding, Examples
Polymorphism in Java with overloading and overriding examples, how the compiler and JVM pick methods, what is not polymorphic, and sealed switch.
Method Hiding in Java: Static Methods vs Overriding
Method hiding in Java happens when a subclass redeclares a static method. See how it differs from overriding, the compiler rules and safer designs.
Difference Between Encapsulation and Abstraction in Java
Learn the difference between encapsulation and abstraction in Java with one thermostat example, a comparison table, getters, records and FAQs.
Difference Between Interface and Abstract Class in Java
Learn the difference between an interface and abstract class in Java 25 with code, a comparison table, default methods, AbstractList and when to use each.
Abstraction in Java: Interfaces and Abstract Classes
Abstraction in Java with interfaces, abstract classes and sealed interfaces, a CSV and JSON export example, a comparison table and common FAQs.