Browse Clojure Foundations for Java Developers

Setting Up the REPL

Build the inner loop: start a REPL, connect your editor, and evaluate code safely.

If you only change one habit from Java to Clojure, make it this: keep a REPL running and use it constantly. The REPL is not a toy console; it is the main way Clojure developers explore code, validate assumptions, and iterate without long compile-run cycles.

What you should be able to do comfortably

  • Start a REPL for a specific project (with the right classpath).
  • Connect your editor so you can evaluate forms quickly.
  • Load/reload a namespace without restarting the whole JVM.
  • Inspect values (including nested maps/vectors) without printing noise.

Java mental model: it is closer to “a live debugger session with a programmable console” than to a script runner.

This section sets up the workflow that makes every later chapter faster and more trustworthy.

In this section

Revised on Friday, April 24, 2026