if (System.getProperty("com.google.appengine.runtime.environment") == null) {
      return false;
    }
    try {
      Class.forName("com.google.appengine.api.utils.SystemProperty");
    } catch (ClassNotFoundException e) {
      return false;
    }
    try {
      // If the current environment is null, we're not inside AppEngine.

      if (theUnsafe.arrayIndexScale(byte[].class) != 1) {
        throw new AssertionError();
      }
    }
  }

  /** Fallback implementation for when Unsafe is not available in our current environment. */
  private enum JavaLittleEndianBytes implements LittleEndianBytes {
    INSTANCE {
      @Override
      public long getLongLittleEndian(byte[] source, int offset) {
        return Longs.fromBytes(

 * string formatting itself should not be a concern.
 *
 * <p>As with any performance concerns, you should consider profiling your code (in a production
 * environment if possible) before spending a lot of effort on tweaking a particular element.
 *
 * <h3>Other types of preconditions</h3>
 *
 * <p>Not every type of precondition failure is supported by these methods. Continue to throw

            method.setAccessible(true);
          } catch (AccessControlException e) {
            // OK: the method is accessible to us anyway. The setAccessible call is only for
            // unusual execution environments where that might not be true.
          }
          builder.put(method.getName(), method);
        }
      }
      typeVariableMethods = builder.buildKeepingLast();
    }

 * href="http://en.wikipedia.org/wiki/Null_Object_pattern">null object</a> for the type in question.
 *
 * <p>This class is not intended as a direct analogue of any existing "option" or "maybe" construct
 * from other programming environments, though it may bear some similarities.
 *
 * <p>An instance of this class is serializable if its reference is absent or is a serializable
 * object.
 *

   *
   * <p>As of jdk7u40, HashMap has an empty-map optimization. The argument to new HashMap(int) is
   * noted, but the initial table is a zero-length array.
   *
   * <p>This test may fail miserably on non-OpenJDK environments...
   */
  @J2ktIncompatible
  @GwtIncompatible // reflection
  @AndroidIncompatible // relies on assumptions about OpenJDK
  public void testNewHashMapWithExpectedSize_wontGrow() throws Exception {

   *
   * <p>As of jdk7u40, HashMap has an empty-map optimization. The argument to new HashMap(int) is
   * noted, but the initial table is a zero-length array.
   *
   * <p>This test may fail miserably on non-OpenJDK environments...
   */
  @J2ktIncompatible
  @GwtIncompatible // reflection
  @AndroidIncompatible // relies on assumptions about OpenJDK
  public void testNewHashMapWithExpectedSize_wontGrow() throws Exception {

    on Linux, with some additional testing on newer JDKs and on Windows. Some
    features, especially in `com.google.common.io`, may not work correctly in
    non-Linux environments. For the Android flavor, our unit tests also run on
    API level 21 (Lollipop).

[guava-snapshot-api-docs]: https://guava.dev/releases/snapshot-jre/api/docs/

   * implemented in terms of that method (though they will likely be overridden by subclasses for
   * performance reasons).) This means that a call to this method have can different behavior in GWT
   * and non-GWT environments UNLESS subclasses are careful to always override all methods
   * implemented in terms of sortedDelegate (except comparator()).
   */
  ImmutableSortedSet(Comparator<? super E> comparator) {

 * href="http://en.wikipedia.org/wiki/Null_Object_pattern">null object</a> for the type in question.
 *
 * <p>This class is not intended as a direct analogue of any existing "option" or "maybe" construct
 * from other programming environments, though it may bear some similarities.
 *
 * <p>An instance of this class is serializable if its reference is absent or is a serializable
 * object.
 *