| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.hadoop.hdfs.util; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| |
| /** |
| * A {@link GSet} is set, |
| * which supports the {@link #get(Object)} operation. |
| * The {@link #get(Object)} operation uses a key to lookup an element. |
| * |
| * Null element is not supported. |
| * |
| * @param <K> The type of the keys. |
| * @param <E> The type of the elements, which must be a subclass of the keys. |
| */ |
| @InterfaceAudience.Private |
| public interface GSet<K, E extends K> extends Iterable<E> { |
| /** |
| * @return The size of this set. |
| */ |
| int size(); |
| |
| /** |
| * Does this set contain an element corresponding to the given key? |
| * @param key The given key. |
| * @return true if the given key equals to a stored element. |
| * Otherwise, return false. |
| * @throws NullPointerException if key == null. |
| */ |
| boolean contains(K key); |
| |
| /** |
| * Return the stored element which is equal to the given key. |
| * This operation is similar to {@link java.util.Map#get(Object)}. |
| * @param key The given key. |
| * @return The stored element if it exists. |
| * Otherwise, return null. |
| * @throws NullPointerException if key == null. |
| */ |
| E get(K key); |
| |
| /** |
| * Add/replace an element. |
| * If the element does not exist, add it to the set. |
| * Otherwise, replace the existing element. |
| * |
| * Note that this operation |
| * is similar to {@link java.util.Map#put(Object, Object)} |
| * but is different from {@link java.util.Set#add(Object)} |
| * which does not replace the existing element if there is any. |
| * |
| * @param element The element being put. |
| * @return the previous stored element if there is any. |
| * Otherwise, return null. |
| * @throws NullPointerException if element == null. |
| */ |
| E put(E element); |
| |
| /** |
| * Remove the element corresponding to the given key. |
| * This operation is similar to {@link java.util.Map#remove(Object)}. |
| * @param key The key of the element being removed. |
| * @return If such element exists, return it. |
| * Otherwise, return null. |
| * @throws NullPointerException if key == null. |
| */ |
| E remove(K key); |
| } |