Java

This Java programming series goes from first classes to production Spring Boot apps. It has more than seventy posts, so it works as a full course.

Early posts cover the language and collections. Later, JDBC fundamentals and JPA and Hibernate add data access. Finally, testing Spring Boot apps ties it all together.

74 articles

23/04/2022 12 min read

Practice: Model a Library System with OOP (Part 1: Domain Design)

Executive Summary: Part 1 of the library system project designs a Java domain model across model and event…
20/03/2022 8 min read

Sealed Classes and Pattern Matching Foundations

Executive Summary: Sealed classes and interfaces in Java list their permitted subtypes, so the compiler knows every variant.…
20/02/2022 8 min read

Records in Java: Immutable Data Carriers Done Right

Executive Summary: A Java record declares an immutable data carrier in one line, and the compiler generates the…
16/01/2022 8 min read

Enums in Java: From Basics to EnumSet and EnumMap

Executive Summary: Java enums define a fixed set of singleton constants that can carry fields, constructors, and per-constant…
01/01/2022 8 min read

Abstract Classes vs Interfaces in Java

Executive Summary: Use an abstract class when related classes share state or a fixed workflow, and an interface…
21/11/2021 9 min read

The Object Class: equals, hashCode, toString, and clone

Executive Summary: Every Java class inherits equals, hashCode, toString, and clone from Object, and the defaults use identity.…
17/10/2021 9 min read

Inheritance and Polymorphism in Java

Executive Summary: In Java, a subclass inherits from its parent, can override its methods, and runs the overridden…
18/09/2021 8 min read

Encapsulation, Access Modifiers, and Packages in Java

Executive Summary: Encapsulation in Java means keeping fields private and exposing behavior through methods that enforce the object’s…
04/09/2021 9 min read

Java Constructors and the this Keyword: Building Objects That Start Valid

Executive Summary: Java constructors initialize objects at creation, and good ones make invalid objects impossible. I cover classes…
15/08/2021 10 min read

Gradle for Java Projects: Builds, Tasks, and Kotlin DSL

Executive Summary: Gradle builds Java projects from a build.gradle.kts file using plugins, repositories, dependencies, and a toolchain that…
01/08/2021 10 min read

Practice: Build a Number Guessing Game in Java

Executive Summary: This beginner project builds a Java number guessing game with Random, a Scanner input loop, replay,…
20/07/2021 10 min read

Maven for Java Projects: From pom.xml to Build Lifecycle

Executive Summary: Maven builds Java projects from a pom.xml that declares coordinates, dependencies, and plugins. I cover transitive…
03/07/2021 10 min read

Practice: Build a CLI Calculator in Java

Executive Summary: This practice project builds a single-file Java CLI calculator with one-shot and interactive modes and switch-expression…
30/05/2021 8 min read

Arrays and Strings in Java (with StringBuilder)

Executive Summary: Java arrays are fixed-length containers with helpers in java.util.Arrays, and Strings are immutable. I cover creating,…