jodd-core/src/main/java/jodd/util/StringUtil.java
public static boolean isSubstringAt(final String string, final String substring, final int offset) {
		int len = substring.length();

		int max = offset + len;

		if (max > string.length()) {
			return false;
		}

		int ndx = 0;
		for (int i = offset; i < max; i++, ndx++) {
			if (string.charAt(i) != substring.charAt(ndx)) {
				return false;
			}
		}

		return true;
	}
public static boolean isSubstringAt(final String string, final String substring, final int offset) {
		int len = substring.length();

		int max = offset + len;

		if (max > string.length()) {
			return false;
		}

		int ndx = 0;
		for (int i = offset; i < max; i++, ndx++) {
			if (string.charAt(i) != substring.charAt(ndx)) {
				return false;
			}
		}

		return true;
	}
Returns <code>true</code> if substring exist at given offset in a string.