private final ByteArrayOutputStream buffer = new ByteArrayOutputStream();

  @SuppressWarnings("DoNotMock")
  @Override
  protected void setUp() throws Exception {
    super.setUp();
    hasher = mock(Hasher.class);
    hashFunction = mock(HashFunction.class);

    when(hashFunction.newHasher()).thenReturn(hasher);
  }

  public void testWrite_putSingleByte() throws Exception {
    int b = 'q';

@NullMarked
public class TestLogHandler extends Handler {
  private final Object lock = new Object();

  /** We will keep a private list of all logged records */
  @GuardedBy("lock")
  private final List<LogRecord> list = new ArrayList<>();

  /** Adds the most recently logged record to our list. */
  @Override
  public void publish(@Nullable LogRecord record) {
    synchronized (lock) {
      if (record != null) {
        list.add(record);
      }

 * [OkHttp Idling Resource](https://github.com/JakeWharton/okhttp-idling-resource): An Espresso IdlingResource for OkHttp.
 * [okhttp-client-mock](https://github.com/gmazzo/okhttp-client-mock): A simple OKHttp client mock, using a programmable request interceptor.
 * [OkHttp Profiler](https://plugins.jetbrains.com/plugin/11249-okhttp-profiler): An IntelliJ plugin for monitoring OkHttp calls.

    // NPE on null listener, so we propagate that contract up into the add method as well.
    checkNotNull(runnable, "Runnable was null.");
    checkNotNull(executor, "Executor was null.");

    // Lock while we check state. We must maintain the lock while adding the new pair so that
    // another thread can't run the list out from under us. We only add to the list if we have not
    // yet started execution.
    synchronized (this) {

        // during the process, though we can't directly test the lock state

        // When
        try {
            curtainBeforeHook.processDBFluteSystem();

            // Then - if we get here without exception, the unlock/lock worked
            DfFinalTimeZoneProvider provider = getDBFluteSystemTimeZoneProvider();

      in.defaultReadObject();
      lock = new Object();
    }

    @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;
  }

  private static final class NonSerializableMemoizingSupplier<T extends @Nullable Object>
      implements Supplier<T> {
    private final Object lock = new Object();

import java.util.logging.Logger;
import org.jspecify.annotations.Nullable;

/** A holder for a {@link Logger} that is initialized only when requested. */
@GwtCompatible
final class LazyLogger {
  private final Object lock = new Object();

  private final String loggerName;
  private volatile @Nullable Logger logger;

  LazyLogger(Class<?> ownerOfLogger) {
    this.loggerName = ownerOfLogger.getName();
  }

  Logger get() {

@GwtCompatible
@NullMarked
public class TearDownStack implements TearDownAccepter {
  private static final Logger logger = Logger.getLogger(TearDownStack.class.getName());

  @VisibleForTesting final Object lock = new Object();

  @GuardedBy("lock")
  final Deque<TearDown> stack = new ArrayDeque<>();

  private final boolean suppressThrows;

  public TearDownStack() {
    this.suppressThrows = false;
  }

@GwtCompatible
@NullMarked
public class TearDownStack implements TearDownAccepter {
  private static final Logger logger = Logger.getLogger(TearDownStack.class.getName());

  @VisibleForTesting final Object lock = new Object();

  @GuardedBy("lock")
  final Deque<TearDown> stack = new ArrayDeque<>();

  private final boolean suppressThrows;

  public TearDownStack() {
    this.suppressThrows = false;
  }

  /**
   * The current state of the service. This should be written with the lock held but can be read
   * without it because it is an immutable object in a volatile field. This is desirable so that
   * methods like {@link #state}, {@link #failureCause} and notably {@link #toString} can be run
   * without grabbing the lock.
   *
   * <p>To update this field correctly the lock must be held to guarantee that the state is
   * consistent.
   */