# 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

    assertThat(record.getMessage()).isEqualTo("message");
    assertThat(record.getThrown()).isEqualTo(EXCEPTION);
  }

  public void testConcurrentModification() throws Exception {
    // Tests for the absence of a bug where logging while iterating over the
    // stored log records causes a ConcurrentModificationException
    assertTrue(handler.getStoredLogRecords().isEmpty());
    ExampleClassUnderTest.foo();

 * caller's responsibility.
 *
 * @author Paul Marks
 * @since 10.0
 */
@Immutable
@GwtCompatible
public final class HostAndPort implements Serializable {
  /** Magic value indicating the absence of a port number. */
  private static final int NO_PORT = -1;

  /** Hostname, IPv4/IPv6 literal, or unvalidated nonsense. */
  private final String host;

  }

  // this doc comment is a modified copy of the inherited doc comment,
  // without the reference to unlimited queues.
  /**
   * Returns the number of additional elements that this queue can ideally (in the absence of memory
   * or resource constraints) accept without blocking. This is always equal to the initial capacity
   * of this queue less the current {@code size} of this queue.
   *

 * operations.
 *
 * <p>Certain cache configurations will result in the accrual of periodic maintenance tasks which
 * will be performed during write operations, or during occasional read operations in the absence of
 * writes. The {@link Cache#cleanUp} method of the returned cache will also perform maintenance, but
 * calling it should not be necessary with a high throughput cache. Only caches built with {@link

        been added for this op. If you were relying on the determinism of the
        `tf.float64` CPU implementation being automatically selected because of
        the absence of the `tf.float64` GPU implementation, you with either need
        to force the op to run on the CPU or use a different data type.

*   Security

    *   Fixes a heap buffer overflow in `RaggedBinCount`

  }

  public void testTransform_absent() {
    assertEquals(Optional.absent(), Optional.absent().transform(Functions.identity()));
    assertEquals(Optional.absent(), Optional.absent().transform(Functions.toStringFunction()));
  }

  public void testTransform_presentIdentity() {
    assertEquals(Optional.of("a"), Optional.of("a").transform(Functions.identity()));
  }

    nextInBucketVToK[src] = ABSENT;
  }

  @Override
  public void clear() {
    Arrays.fill(keys, 0, size, null);
    Arrays.fill(values, 0, size, null);
    Arrays.fill(hashTableKToV, ABSENT);
    Arrays.fill(hashTableVToK, ABSENT);
    Arrays.fill(nextInBucketKToV, 0, size, ABSENT);
    Arrays.fill(nextInBucketVToK, 0, size, ABSENT);
    Arrays.fill(prevInInsertionOrder, 0, size, ABSENT);

  public void testLast() {
    assertEquals(c.getKey(), navigableMap.lastKey());
  }

  @CollectionSize.Require(absent = ZERO)
  public void testHeadMapExclusive() {
    assertFalse(navigableMap.headMap(a.getKey()).containsKey(a.getKey()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testTailMapInclusive() {
    assertTrue(navigableMap.tailMap(a.getKey()).containsKey(a.getKey()));
  }

        com.google.common.base.Optional.absent(),
        generator.generateFresh(new TypeToken<com.google.common.base.Optional<String>>() {}));
    assertEquals(
        com.google.common.base.Optional.of("2"),
        generator.generateFresh(new TypeToken<com.google.common.base.Optional<String>>() {}));
    // Test that the first generated instance for different cgcb.Optional<T> is always absent().