Fundamental Syntax and Concepts

Clojure’s syntax is small, but unfamiliar at first—especially if you expect it to look like Java. This chapter teaches you to read code before you try to write lots of it: lists (code) vs vectors/maps/sets (data), symbols vs keywords, reader literals, and how namespaces structure real programs.

For Java engineers, the key shift is learning to see “shape” quickly: what kind of value is this, what function transforms it, and where the side effects live. Once you can scan Clojure code and predict what it evaluates to, everything else becomes much less mysterious.

Keep a REPL handy and evaluate examples as you go. In Clojure, literacy comes from running small forms and building intuition about values.

In this section

• Symbols and Keywords
  How names and identifiers work in Clojure: symbols, keywords, and when to use each.
  • Understanding Symbols
    Learn how symbols name locals, vars, classes, and code forms in everyday Clojure.
  • Working with Keywords
    Use keywords to model map keys, statuses, and qualified domain labels without stringly typed noise.
  • Symbols vs Keywords
    Separate code names from data labels so Clojure forms become much easier to read and review.
• Data Types
  The core literal types in Clojure and what they map to on the JVM.
  • Clojure Numbers: A Comprehensive Guide for Java Developers
    Explore the numeric types in Clojure, including integers, floating-point numbers, and ratios. Learn about arithmetic operations, type promotion, and how Clojure's approach compares to Java.
  • Clojure Strings: Mastering String Manipulation for Java Developers
    Explore the intricacies of strings in Clojure, including creation, manipulation, and comparison with Java. Learn about string functions, concatenation, and interpolation for efficient text handling.
  • Clojure Characters and Booleans: A Deep Dive for Java Developers
    Explore the intricacies of characters and booleans in Clojure, tailored for Java developers transitioning to functional programming.
• Collections
  Vectors, maps, sets, lists, and sequences—Clojure’s core data structures.
  • Clojure Lists: Understanding and Using Lists in Functional Programming
    Explore the fundamentals of lists in Clojure, a key data structure in functional programming, and learn how to create, access, and utilize them effectively.
  • Clojure Vectors: Efficient Indexed Collections for Java Developers
    Explore Clojure vectors as efficient, indexed, random-access collections. Learn how to create, access, and manipulate vectors, and understand their advantages over Java arrays and lists.
  • Clojure Maps: Key-Value Pairs, Access, and Manipulation
    Explore Clojure maps as key-value pairs, including creation, access, and manipulation techniques for Java developers transitioning to Clojure.
  • Clojure Sets: Unique Collections and Operations
    Explore Clojure sets, their creation, membership checking, and operations like union and intersection, tailored for Java developers transitioning to Clojure.
• Writing Expressions and S-Expressions in Clojure
  Explore how to write expressions and S-expressions in Clojure, understanding their structure and how they differ from Java.
• Commenting Code and Documentation in Clojure
  Learn how to effectively comment and document Clojure code using single-line comments, block comments, and docstrings for functions.
• Namespaces, require, and import
  Organize code with ns and require, keep name origins visible, and use imports only where they improve clarity.
• Clojure Coding Style and Formatting: Best Practices for Java Developers
  Master Clojure coding style and formatting with guidelines on indentation, naming conventions, and auto-formatting tools like cljfmt.
• Key Syntax Differences From Java
  Read Clojure forms on their own terms: prefix notation, expression-oriented code, and data-first structure.
• Clojure Practical Examples and Exercises for Java Developers
  Explore practical Clojure examples and exercises designed for Java developers transitioning to functional programming. Learn through hands-on coding and interactive REPL sessions.
• Clojure Syntax and Concepts: Summary and Key Takeaways for Java Developers
  A comprehensive summary of Clojure's fundamental syntax and concepts, tailored for Java developers transitioning to functional programming.