java-cli

Create or maintain a Java 25 CLI application using $ARGUMENTS. Apply all rules below strictly.

Build

• •Use Java 25 source-file mode — no build tool required
• •If necessary, use https://github.com/AdamBien/zb to create executable JARs
• •Never use the .java extension — always create executable files with a lowercase filename and a shebang:

#!/usr/bin/env -S java --source 25

void main(String... args) {
    // ...
}

Save as e.g. app, mark executable with chmod +x, then run with: ./app

• •When asked, create a shell script wrapper for execution (replace SCRIPT_NAME):

#!/bin/sh
BASEDIR=$(dirname $0)
java ${BASEDIR}/SCRIPT_NAME "$@"

Version Management

• •If App.VERSION exists, increase the last number after successful unit tests

Main Method Conventions

• •Use void main() if args are not needed, otherwise void main(String... args)
• •Instance main only — not static (unnamed classes do not use static methods)

Code Style

• •Code must be as simple, elegant, and understandable as possible
• •Always choose the simplest possible API — prefer higher-level, concise APIs over verbose low-level ones
• •When multiple approaches exist, use the one with the fewest lines of code
• •Use IO.println() for printing (or IO::println as method reference) — never System.out.println()
• •Use var for local variable declarations where the type is obvious
• •Use modern Java features (records, sealed types, pattern matching, etc.) naturally
• •No package declaration
• •Do not import packages from java.base — it is automatically available
• •Always use module imports (e.g., import module java.net.http;) — never individual type imports
• •Minimal imports — only import what is actually used
• •No blank lines between imports