Mega Code Archive
Append, filter and get the size of collections
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/**
* 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.
*/
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.w3c.dom.NodeList;
/**
* A number of helper methods for working with collections
*
* @version $Revision: 747062 $
*/
public final class CollectionHelper {
/**
* Utility classes should not have a public constructor.
*/
private CollectionHelper() {
}
/**
* Returns the size of the collection if it can be determined to be a collection
*
* @param value the collection
* @return the size, or <tt>null</tt> if not a collection
*/
public static Integer size(Object value) {
if (value != null) {
if (value instanceof Collection) {
Collection collection = (Collection)value;
return collection.size();
} else if (value instanceof Map) {
Map map = (Map)value;
return map.size();
} else if (value instanceof Object[]) {
Object[] array = (Object[])value;
return array.length;
} else if (value.getClass().isArray()) {
return Array.getLength(value);
} else if (value instanceof NodeList) {
NodeList nodeList = (NodeList)value;
return nodeList.getLength();
}
}
return null;
}
/**
* Sets the value of the entry in the map for the given key, though if the
* map already contains a value for the given key then the value is appended
* to a list of values.
*
* @param map the map to add the entry to
* @param key the key in the map
* @param value the value to put in the map
*/
@SuppressWarnings("unchecked")
public static void appendValue(Map map, Object key, Object value) {
Object oldValue = map.get(key);
if (oldValue != null) {
List list;
if (oldValue instanceof List) {
list = (List)oldValue;
} else {
list = new ArrayList();
list.add(oldValue);
}
list.add(value);
} else {
map.put(key, value);
}
}
/**
* Filters the given list to skip instanceof filter objects.
*
* @param list the list
* @param filters objects to skip
* @return a new list without the filtered objects
*/
@SuppressWarnings("unchecked")
public static List filterList(List list, Object... filters) {
List answer = new ArrayList();
for (Object o : list) {
for (Object filter : filters) {
if (!o.getClass().isInstance(filter)) {
answer.add(o);
}
}
}
return answer;
}
public static String collectionAsCommaDelimitedString(String[] col) {
if (col == null || col.length == 0) {
return "";
}
return collectionAsCommaDelimitedString(Arrays.asList(col));
}
public static String collectionAsCommaDelimitedString(Collection col) {
if (col == null || col.isEmpty()) {
return "";
}
StringBuilder sb = new StringBuilder();
Iterator it = col.iterator();
while (it.hasNext()) {
sb.append(it.next());
if (it.hasNext()) {
sb.append(",");
}
}
return sb.toString();
}
}
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