xref: /external/guava/guava-testlib/src/com/google/common/collect/testing/TestContainerGenerator.java

/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect.testing;

import java.util.Collection;
import java.util.List;
import java.util.Map;

/**
 * To be implemented by test generators of things that can contain
 * elements. Such things include both {@link Collection} and {@link Map}; since
 * there isn't an established collective noun that encompasses both of these,
 * 'container' is used.
 *
 * <p>This class is GWT compatible.
 *
 * @author George van den Driessche
 */
public interface TestContainerGenerator<T, E> {
  /**
   * Returns the sample elements that this generate populates its container
   * with.
   */
  SampleElements<E> samples();

  /**
   * Creates a new container containing the given elements. TODO: would be nice
   * to figure out how to use E... or E[] as a parameter type, but this doesn't
   * seem to work because Java creates an array of the erased type.
   */
  T create(Object ... elements);

  /**
   * Helper method to create an array of the appropriate type used by this
   * generator. The returned array will contain only nulls.
   */
  E[] createArray(int length);

  /**
   * Returns the iteration ordering of elements, given the order in
   * which they were added to the container. This method may return the
   * original list unchanged, the original list modified in place, or a
   * different list.
   *
   * <p>This method runs only when {@link
   * com.google.common.collect.testing.features.CollectionFeature#KNOWN_ORDER}
   * is specified when creating the test suite. It should never run when testing
   * containers such as {@link java.util.HashSet}, which have a
   * non-deterministic iteration order.
   */
  Iterable<E> order(List<E> insertionOrder);
}