/*
* 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.sshd.common.util;
import java.util.Collection;
import java.util.Collections;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
/**
* A dummy map that ignores all {@code put/remove} calls
*
* @param <K> Key type
* @param <V> Value type
* @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
*/
public class IgnoringEmptyMap<K, V> implements Map<K, V> {
@SuppressWarnings("rawtypes")
private static final IgnoringEmptyMap INSTANCE = new IgnoringEmptyMap();
public IgnoringEmptyMap() {
super();
}
@Override
public int size() {
return 0;
}
@Override
public boolean isEmpty() {
return true;
}
@Override
public boolean containsValue(Object value) {
Objects.requireNonNull(value, "No value provided");
return false;
}
@Override
public boolean containsKey(Object key) {
Objects.requireNonNull(key, "No key provided");
return false;
}
@Override
public V get(Object key) {
Objects.requireNonNull(key, "No key provided");
return null;
}
@Override
public V put(K key, V value) {
Objects.requireNonNull(key, "No key provided");
Objects.requireNonNull(value, "No value provided");
return null;
}
@Override
public V remove(Object key) {
Objects.requireNonNull(key, "No key provided");
return null;
}
@Override
public void putAll(Map<? extends K, ? extends V> m) {
// ignored
}
@Override
public void clear() {
// ignored
}
@Override
public Set<K> keySet() {
return Collections.emptySet();
}
@Override
public Collection<V> values() {
return Collections.emptyList();
}
@Override
public boolean equals(Object o) {
return o instanceof IgnoringEmptyMap<?, ?>;
}
@Override
public int hashCode() {
return 0;
}
@Override
public String toString() {
return "{}";
}
@Override
public Set<Entry<K, V>> entrySet() {
return Collections.emptySet();
}
@SuppressWarnings("unchecked")
public static <K, V> IgnoringEmptyMap<K, V> getInstance() {
return INSTANCE;
}
}