} else {
        // Four-byte form.
        if (index + 2 >= end) {
          return false;
        }
        int byte2 = bytes[index++];
        if (byte2 > (byte) 0xBF
            // Check that 1 <= plane <= 16. Tricky optimized form of:
            // if (byte1 > (byte) 0xF4
            //     || byte1 == (byte) 0xF0 && byte2 < (byte) 0x90
            //     || byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)

   *       for well formed characters. A {@code CharEscaper} should not be used in situations where
   *       input is not guaranteed to be restricted to the Basic Multilingual Plane (BMP).
   * </ul>
   *
   * @param string the literal string to be escaped
   * @return the escaped form of {@code string}
   * @throws NullPointerException if {@code string} is null

      } else {
        // Four-byte form.
        if (index + 2 >= end) {
          return false;
        }
        int byte2 = bytes[index++];
        if (byte2 > (byte) 0xBF
            // Check that 1 <= plane <= 16. Tricky optimized form of:
            // if (byte1 > (byte) 0xF4
            //     || byte1 == (byte) 0xF0 && byte2 < (byte) 0x90
            //     || byte1 == (byte) 0xF4 && byte2 > (byte) 0x8F)

import javax.annotation.CheckForNull;

/**
 * The representation of a linear transformation between real numbers {@code x} and {@code y}.
 * Graphically, this is the specification of a straight line on a plane. The transformation can be
 * expressed as {@code y = m * x + c} for finite {@code m} and {@code c}, unless it is a vertical
 * transformation in which case {@code x} has a constant value for all {@code y}. In the