dsaCalc/src/de/banananetwork/dsa/currencies/CurrencySet.java

package de.banananetwork.dsa.currencies;

import java.util.*;

public class CurrencySet {

	private final Currency[] currencies;

	private CurrencySet(Currency[] currencies) {
		this.currencies = currencies;
	}

	public Map<Currency, Integer> transferToSet(int baseValue) {
		final Map<Currency, Integer> values = new EnumMap<>(Currency.class);
		for (Currency currency : currencies) {
			int value = currency.transferTo(baseValue);
			values.put(currency, value);
			baseValue -= currency.transferFrom(value);
		}
		if (baseValue != 0)
			throw new RuntimeException(); // TODO Change to ValueNotRepresentableException
		return values;
	}

	public static class Builder {

		private List<Currency> currencies = new LinkedList<>();

		public Builder add(Currency currency) {
			this.currencies.add(currency);
			return this;
		}

		public CurrencySet create() {
			return new CurrencySet(currencies.stream().sorted(Comparator.comparing(Currency::getMultiplier).reversed()).toArray(Currency[]::new));
		}

	}

}