/**
* 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);
}