Get Started with Java
Last updated: July 29, 2025
Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.
Get started with mocking and improve your application tests using our Mockito guide:
Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.
Get started with understanding multi-threaded applications with our Java Concurrency guide:
Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:
Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.
But these can also be overused and fall into some common pitfalls.
To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:
Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:
Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.
I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.
You can explore the course here:
Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.
Get started with Spring Data JPA through the guided reference course:
Refactor Java code safely — and automatically — with OpenRewrite.
Refactoring big codebases by hand is slow, risky, and easy to put off. That’s where OpenRewrite comes in. The open-source framework for large-scale, automated code transformations helps teams modernize safely and consistently.
Each month, the creators and maintainers of OpenRewrite at Moderne run live, hands-on training sessions — one for newcomers and one for experienced users. You’ll see how recipes work, how to apply them across projects, and how to modernize code with confidence.
Join the next session, bring your questions, and learn how to automate the kind of work that usually eats your sprint time.
Java is one of the most popular programming languages, often used for building web and enterprise scale applications. This collection of tutorials will help you get started with the basic concepts in Java.
If you are already familiar with the fundamentals, check out the larger Java guide here: Java Tutorial which goes into more detail with each aspect of the language.
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Java Language Basics
- Introduction to Basic Syntax in Java
- Introduction to Java Primitives
- Java main() Method Explained
- Control Structures in Java
- A Guide to Java Loops
- Guide to Java Packages
- Pass-By-Value as a Parameter Passing Mechanism in Java
- Varargs in Java
- Guide to hashCode() in Java
- Java Switch Statement
- Guide to the Java forEach Loop
- Immutable Objects in Java
- A Guide to Java Modularity
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Java OOP
- Java Classes and Objects
- Concrete Class in Java
- Access Modifiers in Java
- A Guide to Constructors in Java
- A Guide to Creating Objects in Java
- Abstract Classes in Java
- Java Interfaces
- Guide to Inheritance in Java
- Inheritance and Composition (Is-a vs Has-a relationship) in Java
- Method Overloading and Overriding in Java
- Composition, Aggregation, and Association in Java
- Guide to the this Java Keyword
- Guide to the super Java Keyword
- A Guide to the Static Keyword in Java
- The “final” Keyword in Java
- Java Record Keyword
- A Guide to Java Enums
- Guide To Java Optional
- Comparing Objects in Java
- Java equals() and hashCode() Contracts
- Functional Interfaces in Java
- Compact Source Files and Instance Main Methods in Java
- Callback Functions in Java
- Pattern Matching for Switch
- Sealed Classes and Interfaces in Java
- Functional Programming in Java
- The transient Keyword in Java
- Java instanceof Operator
- How to Make a Deep Copy of an Object in Java
- Object Type Casting in Java
- Static and Default Methods in Interfaces in Java
- Guide to Java Reflection
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Java Strings
- All About String in Java
- Why String Is Immutable in Java?
- Comparing Strings in Java
- Java String Conversions
- Java toString() Method
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Java Exceptions
- Exception Handling in Java
- Checked and Unchecked Exceptions in Java
- Create a Custom Exception in Java
- Chained Exceptions in Java
- Difference Between Throw and Throws in Java
- Java – Try with Resources
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Java Arrays
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Java Collections
- Guide to the Java ArrayList
- A Guide to the Java LinkedList
- Guide to the Diamond Operator in Java
- Comparator and Comparable in Java
- The Basics of Java Generics
- A Guide to HashSet in Java
- A Guide to Java HashMap
- Initialize a HashMap in Java
- A Guide to Iterator in Java
- Converting Between an Array and a List in Java
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Java Streams
- Introduction to Java Streams
- The Java Stream API Tutorial
- Functional Interfaces in Java
- Guide to Java Collectors
- Java Stream Filter with Lambda Expression
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Java IO
- Read and Write User Input in Java
- How to Read a File in Java
- Java – Create a File
- Java – Write to File
- Introduction to the Java NIO2 File API
- Guide to BufferedReader
- Guide to Java OutputStream
- Introduction to Java Serialization
- Formatting Output with printf() in Java
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Java Development Environment
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