Un exemple de transformation en nombre romain

Converter.java

public class Converter {
	private static class Bound {
		public final int number;
		public final char symbol;
		public Bound(int number, char symbol) {
			super();
			this.number = number;
			this.symbol = symbol;
		}
	}

	private Bound from;
	private Bound through;
	private Bound to;
	private int increment;
	private Converter next;

	public Converter from(int i, char c) {
		this.from = new Bound(i, c);
		this.increment = i;
		return this;
	}
	
	public Converter through(int i, char c) {
		this.through = new Bound(i, c);
		return this;
	}

	public Converter to(int i, char c) {
		this.to = new Bound(i, c);
		return this;
	}

	public boolean containsNumber(int currentNumber) {
		return currentNumber>=from.number;
	}

	public Converter next(Converter next) {
		this.next = next;
		return this;
	}
	public String doConvert(int number) {
		return doConvert(number, new StringBuilder());
	}

	public String doConvert(int number, StringBuilder builder) {
		while(containsNumber(number)) {
			if(number>=to.number) {
				number -= to.number;
				builder.append(to.symbol);
			} else if(number>=to.number-increment) {
				number -= to.number-increment;
				builder.append(from.symbol).append(to.symbol);
			} else if(number>=through.number) {
				number -= through.number;
				builder.append(through.symbol);
			} else if(number>=through.number-increment) {
				number -= through.number-increment;
				builder.append(from.symbol).append(through.symbol);
			} else {
				number -= from.number;
				builder.append(from.symbol);
			}
		}
		if(next!=null) {
			return next.doConvert(number, builder);
		} else {
			return builder.toString();
		}
	}

	public static String convert(int number) {
		Converter converter = new Converter()
				.from(100, 'C')
				.through(500, 'D')
				.to(1000, 'M')
				.next(new Converter()
						.from(10, 'X')
						.through(50, 'L')
						.to(100, 'C')
						.next(new Converter()
								.from(1, 'I')
								.through(5, 'V')
								.to(10, 'X')));
		return converter.doConvert(number);
	}
}