public void testCollisionsDueToIncorrectSignExtension() {
    byte[] col1 = new byte[] {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, (byte) 0x80};
    byte[] col2 = new byte[] {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, (byte) 0x81};
    byte[] col3 = new byte[] {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, (byte) 0xff};

    ImmutableSet<HashCode> hashCodes =
        ImmutableSet.of(

          return 0x80;
        } else if (userFriendly.matches("(?i)(?:French|Latin|Western.*European)")) {
          // Mostly 1-byte UTF-8 sequences, mixed with occasional 2-byte
          // sequences - "Western European" text
          return 0x90;
        } else if (userFriendly.matches("(?i)(?:Branch.*Prediction.*Hostile)")) {
          // Defeat branch predictor for: c < 0x80 ; branch taken 50% of the time.

            // 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)
            || (((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0
            // Third byte trailing-byte test
            || bytes[index++] > (byte) 0xBF
            // Fourth byte trailing-byte test

  public void testIsWellFormed_4BytesSamples() {
    // Valid 4 byte.
    assertWellFormed(0xF0, 0xA4, 0xAD, 0xA2);
    // Bad trailing bytes
    assertNotWellFormed(0xF0, 0xA4, 0xAD, 0x7F);
    assertNotWellFormed(0xF0, 0xA4, 0xAD, 0xC0);
    // Special cases for byte2
    assertNotWellFormed(0xF0, 0x8F, 0xAD, 0xA2);
    assertNotWellFormed(0xF4, 0x90, 0xAD, 0xA2);
  }

  /** Tests some hard-coded test cases. */

  private UnsignedBytes() {}

  /**
   * The largest power of two that can be represented as an unsigned {@code byte}.
   *
   * @since 10.0
   */
  public static final byte MAX_POWER_OF_TWO = (byte) 0x80;

  /**
   * The largest value that fits into an unsigned byte.
   *
   * @since 13.0
   */
  public static final byte MAX_VALUE = (byte) 0xFF;

  private static final int UNSIGNED_MASK = 0xFF;

  /**

          char c3 = input.charAt(i + 3);
          if (c0 < 0x80 && c1 < 0x80 && c2 < 0x80 && c3 < 0x80) {
            update(4, c0 | (c1 << 8) | (c2 << 16) | (c3 << 24));
            i += 4;
          } else {
            break;
          }
        }

        for (; i < utf16Length; i++) {
          char c = input.charAt(i);
          if (c < 0x80) {
            update(1, c);
          } else if (c < 0x800) {

            // 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)
            || (((byte1 << 28) + (byte2 - (byte) 0x90)) >> 30) != 0
            // Third byte trailing-byte test
            || bytes[index++] > (byte) 0xBF
            // Fourth byte trailing-byte test

  public void testIsWellFormed_4BytesSamples() {
    // Valid 4 byte.
    assertWellFormed(0xF0, 0xA4, 0xAD, 0xA2);
    // Bad trailing bytes
    assertNotWellFormed(0xF0, 0xA4, 0xAD, 0x7F);
    assertNotWellFormed(0xF0, 0xA4, 0xAD, 0xC0);
    // Special cases for byte2
    assertNotWellFormed(0xF0, 0x8F, 0xAD, 0xA2);
    assertNotWellFormed(0xF4, 0x90, 0xAD, 0xA2);
  }

  /** Tests some hard-coded test cases. */

      cp >>>= 4;
      dest[10] = UPPER_HEX_DIGITS[0x8 | (cp & 0x3)];
      cp >>>= 2;
      dest[8] = UPPER_HEX_DIGITS[cp & 0xF];
      cp >>>= 4;
      dest[7] = UPPER_HEX_DIGITS[0x8 | (cp & 0x3)];
      cp >>>= 2;
      dest[5] = UPPER_HEX_DIGITS[cp & 0xF];
      cp >>>= 4;
      dest[4] = UPPER_HEX_DIGITS[0x8 | (cp & 0x3)];
      cp >>>= 2;
      dest[2] = UPPER_HEX_DIGITS[cp & 0x7];

          return 0x80;
        } else if (userFriendly.matches("(?i)(?:French|Latin|Western.*European)")) {
          // Mostly 1-byte UTF-8 sequences, mixed with occasional 2-byte
          // sequences - "Western European" text
          return 0x90;
        } else if (userFriendly.matches("(?i)(?:Branch.*Prediction.*Hostile)")) {
          // Defeat branch predictor for: c < 0x80 ; branch taken 50% of the time.