Just what the name says...

StupidDSL

package stupid;

import java.util.*;
import java.util.function.Consumer;

/**
 * A very broken FORTH-like embedded Java DSL
 */
@SuppressWarnings("unchecked")
public enum StupidDSL implements Consumer<ArrayDeque<Object>> {
	
	drop(s -> s.pop()),
	dup(s -> s.push(s.peek())),
	print(s -> {
		((Consumer<ArrayDeque<Object>>) s.pop()).accept(s);
		System.out.println(s.pop());
	}),
	apply(s -> {
		Object o = s.pop();
		if (o instanceof List)
			((List<Consumer<ArrayDeque<Object>>>) o).forEach(a -> a.accept(s));
			else if (o instanceof Consumer) {
				((Consumer<ArrayDeque<Object>>) o).accept(s);
			}
		}),
	swap(s -> {
		Object o2 = s.pop(), o1 = s.pop();
		s.push(o2);
		s.push(o1);
	}),
	compose(s -> {
		List<Consumer<ArrayDeque<Object>>> q2 = (List<Consumer<ArrayDeque<Object>>>) s.pop();
		List<Consumer<ArrayDeque<Object>>> q1 = (List<Consumer<ArrayDeque<Object>>>) s.pop();
		q1.addAll(q2);
		s.push(q1);
	}),
	join(s -> {
		quote((Consumer<ArrayDeque<Object>>) s.pop()).accept(s);
		swap.accept(s);
		quote((Consumer<ArrayDeque<Object>>) s.pop()).accept(s);
		swap.accept(s);
		compose.accept(s);
	}),
	plus(s -> {
		((Consumer<ArrayDeque<Object>>) s.pop()).accept(s);
		Object o2 = s.pop();
		((Consumer<ArrayDeque<Object>>) s.pop()).accept(s);
		Object o1 = s.pop();
		if (o1 instanceof String)
			lit((String) o1 + o2).accept(s);
			else if (o2 instanceof String)
				lit(o1 + (String) o2).accept(s);
			else if (o1 instanceof Integer && o2 instanceof Integer)
				lit((Integer) o1 + (Integer) o2).accept(s);
		}),
	def(s -> {
		((Consumer<ArrayDeque<Object>>) s.pop()).accept(s);
		String name = (String) s.pop();
		List<Consumer<ArrayDeque<Object>>> quotation = (List<Consumer<ArrayDeque<Object>>>) s.pop();
		Wordbank.put(name, a -> a.push(quotation));
	}),
	call(s -> {
		((Consumer<ArrayDeque<Object>>) s.pop()).accept(s);
		String name = (String) s.pop();
		Wordbank.get(name).accept(s);
		apply.accept(s);
	});
	
	/*
	 * Simple hello world demonstrating some of the words
	 */
	public static void main(String[] args) {
		
		List<Consumer<ArrayDeque<Object>>> prog = Arrays.asList(
				quote(lit("Hello World!\n"), lit(21), dup, plus, plus, print), lit("hello"), def,
				lit("hello"), dup, call, call,
				quote(lit(4)), quote(lit(5), plus, print), compose, apply
				);
		
		run(prog);
	}
	
	public static void run(List<Consumer<ArrayDeque<Object>>> program) {
		ArrayDeque<Object> stack = new ArrayDeque<>();
		
		program.iterator().forEachRemaining(s -> s.accept(stack));
	}
	
	@SafeVarargs
	public static Consumer<ArrayDeque<Object>> quote(Consumer<ArrayDeque<Object>>... a) {
		List<Consumer<ArrayDeque<Object>>> quotation = new ArrayList<>();
		for (Consumer<ArrayDeque<Object>> c : a)
			quotation.add(c);
		return s -> s.push(quotation);
	}
	
	public static Consumer<ArrayDeque<Object>> lit(Object a) {
		return z -> z.push((Consumer<ArrayDeque<Object>>) s -> s.push(a));
	}
	
	private static class Wordbank {
		private static final Map<String, Consumer<ArrayDeque<Object>>> instance = new HashMap<>();
		
		static void put(String name, Consumer<ArrayDeque<Object>> word) {
			instance.put(name, word);
		}
		
		static Consumer<ArrayDeque<Object>> get(Object name) {
			return instance.get(name);
		}
	}
	
	static {
		for (StupidDSL word : StupidDSL.values())
			Wordbank.put(word.name(), word);
	}
	
	private final Consumer<ArrayDeque<Object>> c;
	
	private StupidDSL(Consumer<ArrayDeque<Object>> c) {
		this.c = c;
	}
	
	@Override
	public void accept(ArrayDeque<Object> t) {
		c.accept(t);
	}
}