Method codePointBefore

lib/java/lang/Character.java:2303–2321

Returns the code point that preceds index in the specified sequence of character units. If the unit at index - 1 is a low-surrogate unit, index - 2 is not negative and the unit at index - 2 is a high-surrogate unit, then the supplementary code point represented by the

(CharSequence seq, int index)

     * @since 1.5
     */
    public static int codePointBefore(CharSequence seq, int index) {
        if (seq == null) {
            throw new NullPointerException();
        }
        int len = seq.length();
        if (index < 1 || index > len) {
            throw new StringIndexOutOfBoundsException(index);
        }

        char low = seq.charAt(--index);
        if (--index < 0) {
            return low;
        }
        char high = seq.charAt(index);
        if (isSurrogatePair(high, low)) {
            return toCodePoint(high, low);
        }
        return low;
    }

    /**
     * Returns the code point that preceds {@code index} in the specified