@Override
  public int hashCode() {
    return delegate.hashCode();
  }

  private void validate() {
    // Don't use checkState(), because we don't want the overhead of generating the error message
    // unless it's actually going to be used; validate() is called for all set method calls, so it
    // needs to be fast.
    // (We could instead generate the message once, when the set is created, but zero is better.)

 *
 * <p><b>Warning:</b> The caller is responsible for not attempting to read past the end of the
 * array. If any method encounters the end of the array prematurely, it throws {@link
 * IllegalStateException} to signify <i>programmer error</i>. This behavior is a technical violation
 * of the supertype's contract, which specifies a checked exception.
 *
 * @author Kevin Bourrillion
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible

   *
   * @return a {@code String} containing the contents of the line, not including any
   *     line-termination characters, or {@code null} if the end of the stream has been reached.
   * @throws IOException if an I/O error occurs
   */
  @CanIgnoreReturnValue // to skip a line
  @CheckForNull
  public String readLine() throws IOException {
    while (lines.peek() == null) {
      Java8Compatibility.clear(cbuf);

  // Load factor and capacity for "inner" (i.e. per node/edge element) hash sets or maps
  static final float INNER_LOAD_FACTOR = 1.0f;
  static final int INNER_CAPACITY = 2; // ceiling(EXPECTED_DEGREE / INNER_LOAD_FACTOR)

  // Error messages
  static final String NODE_NOT_IN_GRAPH = "Node %s is not an element of this graph.";
  static final String EDGE_NOT_IN_GRAPH = "Edge %s is not an element of this graph.";
  static final String NODE_REMOVED_FROM_GRAPH =

    <dependency>
      <groupId>org.checkerframework</groupId>
      <artifactId>checker-qual</artifactId>
    </dependency>
    <dependency>
      <groupId>com.google.errorprone</groupId>
      <artifactId>error_prone_annotations</artifactId>
    </dependency>
    <dependency>
      <groupId>com.google.j2objc</groupId>
      <artifactId>j2objc-annotations</artifactId>
    </dependency>
    <dependency>

 * ExecutionException} when the exception thrown by a task is an unchecked exception. However, it
 * may also wrap a checked exception in some cases.
 *
 * <p>When wrapping an {@code Error} from another thread, prefer {@link ExecutionError}. When
 * wrapping a checked exception, prefer {@code ExecutionException}.
 *
 * @author Charles Fry
 * @since 10.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

    <dependency>
      <groupId>org.checkerframework</groupId>
      <artifactId>checker-qual</artifactId>
    </dependency>
    <dependency>
      <groupId>com.google.errorprone</groupId>
      <artifactId>error_prone_annotations</artifactId>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13.2</version>
      <scope>test</scope>
    </dependency>

    }
  }

  public void testNulls() {
    /*
     * Don't bother testing. All non-primitive parameters are used only to construct error messages.
     * We never want to pass null for them, so we haven't annotated them to say that null is
     * allowed. But at the same time, it seems wasteful to bother inserting the checkNotNull calls

  @Override
  public void setUp() throws Exception {
    super.setUp();
    this.equivalenceMock = new MockEquivalence();
    this.tester = EquivalenceTester.of(equivalenceMock);
  }

  /** Test null reference yields error */
  public void testOf_NullPointerException() {
    try {
      EquivalenceTester.of(null);
      fail("Should fail on null reference");
    } catch (NullPointerException expected) {
    }
  }

  @Override
  public void setUp() throws Exception {
    super.setUp();
    this.equivalenceMock = new MockEquivalence();
    this.tester = EquivalenceTester.of(equivalenceMock);
  }

  /** Test null reference yields error */
  public void testOf_NullPointerException() {
    try {
      EquivalenceTester.of(null);
      fail("Should fail on null reference");
    } catch (NullPointerException expected) {
    }
  }