Good-enough command line argument parsing in about a page of Java

Opts.java

// This is kind of shaped like lexopt: https://github.com/blyxxyz/lexopt

sealed interface Opt permits ShortOpt, LongOpt, MiscOpt {
	default boolean isShort(char c) { return this instanceof ShortOpt o && o.opt == c; }
	default boolean isLong(String l) { return this instanceof LongOpt o && o.opt.equals(l); }
}
record ShortOpt(char opt) implements Opt {}  //the "a", "b", or "c" in "-abc"
record LongOpt(String opt) implements Opt {} //the "option" in "--option"
record MiscOpt(String etc) implements Opt {} //something without a hyphen prefix

class OptLexer implements Iterator<Opt>, Iterable<Opt> {
	public OptLexer(String[] args) { this.args = args; }
	private final String[] args;

	enum Mode {READY, SHORT}
	private Mode mode = Mode.READY;
	private int idx = 0, subitem = 0;

	@Override
	public boolean hasNext() {
		return idx < args.length;
	}

	@Override
	public Opt next() {
		String currentArg = args[idx];
		return switch(mode) {
			case READY -> {
				if(currentArg.startsWith("--")) {
					idx++;
					yield new LongOpt(currentArg.substring(2));
				} else if(currentArg.startsWith("-")) {
					mode = Mode.SHORT;
					subitem = 1;
					yield next();
				} else {
					idx++;
					yield new MiscOpt(currentArg);
				}
			}
			case SHORT -> {
				ShortOpt shortOpt = new ShortOpt(currentArg.charAt(subitem));
				subitem++;
				if(subitem == currentArg.length()) {
					mode = Mode.READY;
					idx++;
				}
				yield shortOpt;
			}
		};
	}

	public String value() {
		return switch(mode) {
			case SHORT -> {
				String value = args[idx].substring(subitem);
				mode = Mode.READY;
				idx++;
				yield value.isEmpty() ? null : value;
			}
			case READY -> hasNext() ? args[idx++] : null;
		};
	}

	@Override
	public Iterator<Opt> iterator() {
		return this;
	}
}

Opts_Java8.java

// Java 8 compatible

interface Opt {
	default boolean isShort(char c) { return this instanceof ShortOpt && ((ShortOpt) this).opt == c; }
	default boolean isLong(String l) { return this instanceof LongOpt && ((LongOpt) this).opt.equals(l); }
}
class ShortOpt implements Opt {
	public ShortOpt(char opt) { this.opt = opt; }
	public char opt;
	@Override public String toString() { return "ShortOpt " + opt; }
}
class LongOpt implements Opt {
	public LongOpt(String opt) { this.opt = opt; }
	public String opt;
	@Override public String toString() { return "LongOpt " + opt; }
}
class MiscOpt implements Opt {
	public MiscOpt(String etc) { this.etc = etc; }
	public String etc;
	@Override public String toString() { return "MiscOpt " + opt; }
}

class OptLexer implements Iterator<Opt>, Iterable<Opt> {
	public OptLexer(String[] args) { this.args = args; }
	private final String[] args;
	
	enum Mode {READY, SHORT}
	private Mode mode = Mode.READY;
	private int idx = 0, subitem = 0;
	
	@Override
	public boolean hasNext() {
		return idx < args.length;
	}

	@Override
	public Opt next() {
		while(true) {
			String currentArg = args[idx];
			switch(mode) {
				case READY:
					if(currentArg.startsWith("--")) {
						idx++;
						return new LongOpt(currentArg.substring(2));
					} else if(currentArg.startsWith("-")) {
						mode = Mode.SHORT;
						subitem = 1;
						continue;
					} else {
						idx++;
						return new MiscOpt(currentArg);
					}
				case SHORT:
					ShortOpt shortOpt = new ShortOpt(currentArg.charAt(subitem));
					subitem++;
					if(subitem == currentArg.length()) {
						mode = Mode.READY;
						idx++;
					}
					return shortOpt;
			}
		}
	}

	public String value() {
		if(mode == Mode.SHORT) {
			String value = args[idx].substring(subitem);
			mode = Mode.READY;
			idx++;
			return value.isEmpty() ? null : value;
		} else {
			return hasNext() ? args[idx++] : null;
		}
	}

	@Override
	public Iterator<Opt> iterator() {
		return this;
	}
}

Usage.java

public static void main(String[] args) {
	OptLexer lexer = new OptLexer(args);
	for(Opt opt : lexer) {
		if(opt.isShort('h') || opt.isLong("help")) // -h, --help
			System.out.println("Usage: (...)");
		else if(opt.isLong("key")) // --key value
			System.out.println("value: " + lexer.value());
		else if(opt.isShort('O')) // -Ofast
			System.out.println(lexer.value());
		else System.out.println("unrecognized option " + opt);
	}
}