void (final int id, final Data value, final boolean overrideExisting) { if (!overrideExisting) { if (valueById.containsKey(id)) { throw new IllegalArgumentException( "id(=" + id + ") is already in use (value: " + valueById.get(id) + ") -- use overrideExisting=true"); } } idByValue.put(value, id); valueById.put(id, value); }