SubstringSample.java

/**
 * Returns a new string that is a substring of this string.
 * The surrogate pair is taken into consideration.
 */
final class SubstringSample {
	static String substring(String source, int startCodePoints) {
		final int endCodePoints = source.codePointCount(0, source.length());
		return substring(source, startCodePoints, endCodePoints);
	}

	static String substring(String source, int startCodePoints, int endCodePoints) {
		final int startIndex = source.offsetByCodePoints(0, startCodePoints);
		final int endIndex = source.offsetByCodePoints(startIndex, endCodePoints - startCodePoints);
		return source.substring(startIndex, endIndex);
	}
}