/*
* Copyright 2011-14 Eric F. Savage, code@efsavage.com
*
* 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.ajah.lang;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.logging.Level;
import lombok.extern.java.Log;
/**
* Extension of {@link HashMap} that has a methods to make dealing with the
* value lists easier.
*
* @author <a href="http://efsavage.com">Eric F. Savage</a>, <a
* href="mailto:code@efsavage.com">code@efsavage.com</a>.
*
* @param <K>
* @param <V>
*/
@Log
public class ListMap<K, V> extends ConcurrentHashMap<K, List<V>> {
/**
* Returns the list found at the specified key or an empty list. Avoids
* {@link NullPointerException} for iterators.
*
* If no list is found, {@link Collections#emptyList()} will be returned. If
* an empty, mutable list is desired, use {@link #getList(Object, Class)}.
*
* @param key
* The key to look up the value list.
* @return The value list, may be empty, will not be null.
*/
public List<V> getList(final K key) {
final List<V> list = get(key);
if (list == null) {
return Collections.emptyList();
}
return list;
}
/**
* Returns the list found at the specified key or an empty list. Avoids
* {@link NullPointerException} for iterators.
*
* @param key
* The key to look up the value list.
* @param listClass
* The class of list to return if one needs to be created.
* @return The value list, may be empty, will not be null.
*/
public List<V> getList(final K key, final Class<? extends List<V>> listClass) {
List<V> list = get(key);
if (list == null) {
try {
list = listClass.newInstance();
put(key, list);
} catch (InstantiationException | IllegalAccessException e) {
log.log(Level.SEVERE, e.getMessage(), e);
}
}
return list;
}
/**
* Adds a value to the list for a given key, creating that list if
* necessary.
*
* @param key
* The key to look up the value list.
* @param value
* The value to add to the list.
*/
public void putValue(final K key, final V value) {
List<V> list = get(key);
if (list == null) {
list = new ArrayList<>();
put(key, list);
}
list.add(value);
}
/**
* Returns the total number of values across all keys.
*
* @return The total number of values across all keys.
*/
public int valuesSize() {
int size = 0;
for (final K key : keySet()) {
size += get(key) == null ? 0 : get(key).size();
}
return size;
}
}