zargs

Add zero-dependency argument parsing to a Java CLI application using $ARGUMENTS. Apply all rules below.

What is zargs

zargs is a zero-dependency, enum-based argument parsing pattern for Java CLI applications. It is not a library or dependency — it is a set of conventions and code patterns to apply directly when generating argument parsing code.

• Reference: https://github.com/AdamBien/zeeds/blob/main/zargs
• Requires: Java 21+

Argument Enum Pattern

Define an enum where each constant represents a CLI option. The enum provides matching, lookup, and usage generation:

import java.util.stream.Collectors;
import java.util.stream.Stream;

public enum Arg {
    HELP("-help", "Show this help"),
    VERBOSE("-verbose", "Enable verbose output"),
    OUTPUT("-output", "Specify output file");

    final String option;
    final String description;

    Arg(String option, String description) {
        this.option = option;
        this.description = description;
    }

    boolean matches(String value) {
        return this.option.equals(value)
            || value.startsWith(this.option + ":");
    }

    static Arg from(String value) {
        return Stream.of(values())
            .filter(a -> a.matches(value))
            .findFirst()
            .orElse(null);
    }

    static String usage() {
        return Stream.of(values())
            .map(a -> "  %-12s %s".formatted(a.option, a.description))
            .collect(Collectors.joining("\n"));
    }
}

Parsed Arguments Record

Define a record matching the application's parsed arguments:

import java.util.List;

public record Args(boolean verbose, String output, List<String> files) {}

Argument Syntax

zargs supports two value styles for options that take a value:

Style	Example	Description
Colon-separated	-output:result.txt	Value follows : immediately
Space-separated	-output result.txt	Value is the next argument

Boolean flags (like -verbose) require no value.