checkNotClosed();
    target.append(charSeq, start, end);
    return this;
  }

  private void checkNotClosed() throws IOException {
    if (closed) {
      throw new IOException("Cannot write to a closed writer.");
    }
  }

  }

  public void testIndexOfImpl_null() {
    List<String> toTest;
    try {
      toTest = createList(String.class, null, "A", "B", null, "C", null);
    } catch (NullPointerException e) {
      // example cannot handle nulls, test invalid
      return;
    }
    int[] expected = {0, 1, 2, 0, 4, 0};
    checkIndexOf(toTest, expected);
  }

  public void testLastIndexOfImpl_nonNull() {

 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
/*
 * 1. The type parameter is <T> rather than <T extends @Nullable> so that we can use T in the
 * doForward and doBackward methods to indicate that the parameter cannot be null. (We also take
 * advantage of that for convertAll, as discussed on that method.)
 *
 * 2. The supertype of this class could be `Function<@Nullable A, @Nullable B>`, since

 * therefore every method of the listener will be called at most once. N.B. The {@link State#FAILED}
 * and {@link State#TERMINATED} states are terminal states, once a service enters either of these
 * states it cannot ever leave them.
 *
 * <p>Implementors of this interface are strongly encouraged to extend one of the abstract classes
 * in this package which implement this interface and make the threading and state management
 * easier.

     *
     * <p>After calling this method, you can keep adding more properties to later call toString()
     * again and get a more complete representation of the same object; but properties cannot be
     * removed, so this only allows limited reuse of the helper instance. The helper allows
     * duplication of properties (multiple name/value pairs with the same name can be added).
     */
    @Override

import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@code SetMultimap} whose set of values for a given key are kept sorted; that is, they comprise
 * a {@link SortedSet}. It cannot hold duplicate key-value pairs; adding a key-value pair that's
 * already in the multimap has no effect. This interface does not specify the ordering of the

   *   <li>eliminating the error-prone caching boilerplate
   *   <li>tracking load {@linkplain #stats statistics}
   * </ul>
   *
   * <p>Among the further improvements that {@code LoadingCache} can provide but this method cannot:
   *
   * <ul>
   *   <li>consolidation of the loader logic to {@linkplain CacheBuilder#build(CacheLoader) a single
   *       authoritative location}

    // space is a safe character then setting plusForSpace is meaningless.
    if (plusForSpace && safeChars.contains(" ")) {
      throw new IllegalArgumentException(
          "plusForSpace cannot be specified when space is a 'safe' character");
    }
    this.plusForSpace = plusForSpace;
    this.safeOctets = createSafeOctets(safeChars);
  }

  /**

          notices within Derivative Works that You distribute, alongside
          or as an addendum to the NOTICE text from the Work, provided
          that such additional attribution notices cannot be construed
          as modifying the License.

      You may add Your own copyright statement to Your modifications and
      may provide additional or different license terms and conditions

 *   x = null;  // Hint to the JIT that x is stack-unreachable
 *   return weakRef;
 * }
 * public void testFooLeak() {
 *   GcFinalization.awaitClear(fooWeakRef());
 * }
 * }</pre>
 *
 * <p>This class cannot currently be used to test soft references, since this class does not try to
 * create the memory pressure required to cause soft references to be cleared.
 *