Elegant Java
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Elegant Java

Hands-on Guide to write Clean Code in Java

About the Book

Nothing affects the work of a team as much as bad, illegible, sloppy, and quickly written code that has not been designed carefully. Team dynamics can be improved, requirements can be redefined, and the schedule can be modified. However, if bad code takes over, it becomes more and more a burden for the team.

Programmers should develop all the time. Even if they think that they have sufficient skills and knowledge to move around in current projects, they should not stop there, and it is worthwhile for them to learn new concepts, approaches, language, and frameworks from time to time. Learning should be a journey and not a destination.

This book discusses the best practices of writing better code. It also contains many code examples in Java of increasing complexity.

This is a Forever Edition. That means that the book will see periodic updates, which are free for you. The book will use the latest Java version for the examples provided.

About the Author

Martin Hock
Martin Hock

Martin is a principal software engineer with over 20 years of experience in application design and development. His primary focus is on lightweight Java and open source technologies with expertise in software architecture, web technologies, and the Spring ecosystem.


He has found that teaching is the best way to learn software development. He is a part-time lecturer at two universities and teaches courses on Java, Software Craftsmanship and Clean Code.

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Table of Contents

  • Preface
    • What about the code examples and typographic conventions?
    • Which literature is this book based on?
    • Giving feedback?
  • 1 Java Best Practices
    • 1.1 Avoid instantiation for utility classes
    • 1.2 Use immutable objects
    • 1.3 Prefer records for immutability
    • 1.4 Provide immutable decorators for sensitive mutable classes
    • 1.5 Consider using sealed classes and interfaces
    • 1.6 Avoid constant interfaces
    • 1.7 Avoid global constant classes
    • 1.8 Favour composition over inheritance
    • 1.9 Consider using lambdas
    • 1.10 Use meaningful return types
    • 1.11 Use the @Override Annotation
    • 1.12 Use the @FunctionalInterface Annotation
    • 1.13 Prefer returning Null-Objects over null
    • 1.14 Avoid null as a method parameter
    • 1.15 Prefer enhanced loops over for loops
    • 1.16 Code against interfaces not implementations
    • 1.17 Use existing exceptions
    • 1.18 Validate method parameter
    • 1.19 Minimize method parameters for improved readability
    • 1.20 Prevent NullPointerException for String comparison
    • 1.21 Safely cast long to int
    • 1.22 Convert integers to floating-point for floating-point math operations
    • 1.23 Use generics in favor of raw types
    • 1.24 Prefer enums over int constants
    • 1.25 Prefer the == operator over equals for comparing enum values
    • 1.26 Be aware of the contract between equals and hashCode
    • 1.27 Use text blocks for multi-line strings
    • 1.28 Use always braces for the body of all statements
    • 1.29 Simplifying boolean expressions
    • 1.30 Pre-calculate the length in loops
    • 1.31 Avoid constructor instantiation of String
    • 1.32 Use StringBuilder for concatenation
    • 1.33 Reduce lookups in collection containers
    • 1.34 Instantiate wrapper objects with valueOf
    • 1.35 Use entrySet for iterating
    • 1.36 Use isEmpty() for String length
    • 1.37 Avoid using the default case in switch statements for sealed classes
    • 1.38 Prefer method references over lambdas for conciseness
    • 1.39 Use the orElse and orElseGet methods for optional values
    • 1.40 Enhance code clarity with EnumMap
  • Notes

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