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(

  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(

                (byte) 0x05, (byte) 0x06, (byte) 0x07, (byte) 0x08
              },
              0x89abcdef,
              0x0123456789abcdefL, // asInt/asLong as above, due to equal eight first bytes
              "efcdab89674523010102030405060708"),
          new ExpectedHashCode(
              new byte[] {(byte) 0xdf, (byte) 0x9b, (byte) 0x57, (byte) 0x13},
              0x13579bdf,
              null,

                (byte) 0x05, (byte) 0x06, (byte) 0x07, (byte) 0x08
              },
              0x89abcdef,
              0x0123456789abcdefL, // asInt/asLong as above, due to equal eight first bytes
              "efcdab89674523010102030405060708"),
          new ExpectedHashCode(
              new byte[] {(byte) 0xdf, (byte) 0x9b, (byte) 0x57, (byte) 0x13},
              0x13579bdf,
              null,

        new byte[] {
          0x01, (byte) 0xc0, 0x00, 0x00,
          0x00, 0x00, 0x00, 0x00,
          0x00, 0x00, 0x00, 0x00,
          0x00, 0x00, 0x00, 0x00,
          0x14, 0x00, 0x00, 0x00,
          0x00, 0x00, 0x04, 0x00,
          0x00, 0x00, 0x00, 0x14,
          0x00, 0x00, 0x00, 0x18,
          0x28, 0x00, 0x00, 0x00,
          0x00, 0x00, 0x00, 0x00,
          0x02, 0x00, 0x00, 0x00,

# ADR-0008 - Use NullAway for null checking

## Status

- ACCEPTED on 2025-08-06

## Context

Our codebase uses `null` extensively to represent an absence of value or optionality of the argument.
We utilize nullness annotations in Java code and somewhat rely on IDE warnings to guide us.
However, the Java code we have is not fully annotated, which causes several consequences:
* IDE warnings can be misleading

    hasher = HASH_FN.newHasher();
    hasher
        .putByte((byte) 0x01)
        .putByte((byte) 0x01)
        .putByte((byte) 0x00)
        .putByte((byte) 0x01)
        .putByte((byte) 0x00)
        .putByte((byte) 0x00)
        .putByte((byte) 0x00)
        .putByte((byte) 0x00);
    assertEquals(hashCode, hasher.hash().asLong());

    hasher = HASH_FN.newHasher();
    hasher

      return false;
    }

    byte[] bytes = ip.getAddress();

    if ((bytes[8] | (byte) 0x03) != (byte) 0x03) {

      // Verify that high byte of the 64 bit identifier is zero, modulo
      // the U/L and G bits, with which we are not concerned.
      return false;
    }

    return (bytes[9] == (byte) 0x00) && (bytes[10] == (byte) 0x5e) && (bytes[11] == (byte) 0xfe);
  }

  /**

   * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
   * example, {@code [] < [0x01] < [0x01, 0x7F] < [0x01, 0x80] < [0x02]}. Values are treated as
   * unsigned.
   *
   * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays

    // Empty
    assertWellFormed();
    // One-byte characters, including control characters
    assertWellFormed(0x00, 0x61, 0x62, 0x63, 0x7F); // "\u0000abc\u007f"
    // Two-byte characters
    assertWellFormed(0xC2, 0xA2, 0xC2, 0xA2); // "\u00a2\u00a2"
    // Three-byte characters
    assertWellFormed(0xc8, 0x8a, 0x63, 0xc8, 0x8a, 0x63); // "\u020ac\u020ac"
    // Four-byte characters
    // "\u024B62\u024B62"