Java Implementation of indexOf()

indexOf.java

public int indexOf(int ch, int fromIndex) {
  if (fromIndex < 0) {
      fromIndex = 0;
  } else if (fromIndex >= count) {
      // Note: fromIndex might be near -1>>>1.
      return -1;
  }

  if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
      // handle most cases here (ch is a BMP code point or a
      // negative value (invalid code point))
      final char[] value = this.value;
      final int offset = this.offset;
      final int max = offset + count;
      for (int i = offset + fromIndex; i < max ; i++) {
          if (value[i] == ch) {
              return i - offset;
          }
      }
      return -1;
  } else {
      return indexOfSupplementary(ch, fromIndex);
  }
}

/**
* Handles (rare) calls of indexOf with a supplementary character.
*/
private int indexOfSupplementary(int ch, int fromIndex) {
  if (Character.isValidCodePoint(ch)) {
      final char[] value = this.value;
      final int offset = this.offset;
      final char hi = Character.highSurrogate(ch);
      final char lo = Character.lowSurrogate(ch);
      final int max = offset + count - 1;
      for (int i = offset + fromIndex; i < max; i++) {
          if (value[i] == hi && value[i+1] == lo) {
              return i - offset;
          }
      }
  }
  return -1;
}