}

  @Override
  public UnmodifiableIterator<E> iterator() {
    E connectingEdge = getConnectingEdge();
    return (connectingEdge == null)
        ? ImmutableSet.<E>of().iterator()
        : Iterators.singletonIterator(connectingEdge);
  }

  @Override
  public int size() {
    return getConnectingEdge() == null ? 0 : 1;
  }

  @Override
  public boolean contains(@Nullable Object edge) {

    }.test();
  }

  public void testConcatPartiallyAdvancedSecond() {
    Iterator<String> itr1 = Iterators.concat(singletonIterator("a"), Iterators.forArray("b", "c"));
    assertEquals("a", itr1.next());
    assertEquals("b", itr1.next());
    Iterator<String> itr2 = Iterators.concat(singletonIterator("d"), itr1);
    assertEquals("d", itr2.next());
    assertEquals("c", itr2.next());
  }

  }

  @Override
  public UnmodifiableIterator<E> iterator() {
    E connectingEdge = getConnectingEdge();
    return (connectingEdge == null)
        ? ImmutableSet.<E>of().iterator()
        : Iterators.singletonIterator(connectingEdge);
  }

  @Override
  public int size() {
    return getConnectingEdge() == null ? 0 : 1;
  }

  @Override
  public boolean contains(@Nullable Object edge) {

  public static <T extends @Nullable Object> UnmodifiableIterator<T> singletonIterator(
      @ParametricNullness T value) {
    return new SingletonIterator<>(value);
  }

  private static final class SingletonIterator<T extends @Nullable Object>
      extends UnmodifiableIterator<T> {
    private final T value;
    private boolean done;

    SingletonIterator(T value) {
      this.value = value;
    }

 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.collect.Iterators.singletonIterator;
import static com.google.common.collect.ReflectionFreeAssertThrows.assertThrows;
import static com.google.common.collect.testing.Helpers.testComparator;
import static com.google.common.testing.SerializableTester.reserialize;

 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.collect.Iterators.singletonIterator;
import static com.google.common.collect.ReflectionFreeAssertThrows.assertThrows;
import static com.google.common.collect.testing.Helpers.testComparator;
import static com.google.common.testing.SerializableTester.reserialize;