*
 * <p>If the precondition is not met, the {@code Preconditions} method throws an unchecked exception
 * of a specified type, which helps the method in which the exception was thrown communicate that
 * its caller has made a mistake. This allows constructs such as
 *
 * <pre>{@code
 * public static double sqrt(double value) {
 *   if (value < 0) {
 *     throw new IllegalArgumentException("input is negative: " + value);
 *   }

            Serialization.getFieldSetter(ImmutableSetMultimap.class, "emptySet");
  }

  @GwtIncompatible // java.io.ObjectInputStream
  @J2ktIncompatible
  // Serialization type safety is at the caller's mercy.
  @SuppressWarnings("unchecked")
  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
    stream.defaultReadObject();

   * The {@link Iterators} analog to this method is {@link Iterators#getNext}.
   *
   * <p>If no default value is desired (and the caller instead wants a {@link
   * NoSuchElementException} to be thrown), it is recommended that {@code
   * iterable.iterator().next()} is used instead.
   *

   * Optional.orElseGet}, except when {@code supplier} returns {@code null}. In this case this
   * method throws an exception, whereas the Java 8+ method returns the {@code null} to the caller.
   *
   * @throws NullPointerException if this optional's value is absent and the supplier returns {@code
   *     null}
   */
  public abstract T or(Supplier<? extends T> supplier);

  /**

      thrownUnsafeFailure = unsafeFailure;
      // catch absolutely everything and fall through to our 'SafeAtomicHelper'
      // The access control checks that ARFU does means the caller class has to be AbstractFuture
      // instead of SafeAtomicHelper, so we annoyingly define these here
      try {
        helper =
            new SafeAtomicHelper(

    otherwise. Do not persist these and assume they can be read by a future
    version of the library.

5.  Our classes are not designed to protect against a malicious caller. You
    should not use them for communication between trusted and untrusted code.

6.  For the mainline flavor, we test the libraries using OpenJDK 8, 11, and 17

            Serialization.getFieldSetter(ImmutableSetMultimap.class, "emptySet");
  }

  @GwtIncompatible // java.io.ObjectInputStream
  @J2ktIncompatible
  // Serialization type safety is at the caller's mercy.
  @SuppressWarnings("unchecked")
  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
    stream.defaultReadObject();

   * {@code invokeAny}. In the latter case, tasks will run serially on the calling thread. Tasks are
   * run to completion before a {@code Future} is returned to the caller (unless the executor has
   * been shutdown).
   *
   * <p>Although all tasks are immediately executed in the thread that submitted the task, this

   * would declare a return type of `@Nullable T[]`. However, we've decided not to think too hard
   * about arrays for now, as they're a mess. (We previously discussed this in the review of
   * ObjectArrays, which is the main caller of this method.)
   */
  static <T extends @Nullable Object> T[] newArray(T[] reference, int length) {
    T[] empty = reference.length == 0 ? reference : Arrays.copyOf(reference, 0);
    return Arrays.copyOf(empty, length);

  //    visible to done(). This is because there is no happens before edge between the write and a
  //    (hypothetical) unsafe read by our caller. Note: adding 'volatile' does not fix this issue,
  //    it would just add an edge such that if done() observed non-null, then it would also