import java.util.Arrays;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;
/*
* Copyright 2002-2007 the original author or authors.
*
* 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.
*/
/**
* Miscellaneous collection utility methods.
* Mainly for internal use within the framework.
*
* @author Juergen Hoeller
* @author Rob Harrop
* @since 1.1.3
*/
abstract class CollectionUtils {
/**
* Find a value of the given type in the given Collection.
* @param collection the Collection to search
* @param type the type to look for
* @return a value of the given type found, or null if none
* @throws IllegalArgumentException if more than one value of the given type found
*/
public static Object findValueOfType(Collection collection, Class type) throws IllegalArgumentException {
if (isEmpty(collection)) {
return null;
}
Class typeToUse = (type != null ? type : Object.class);
Object value = null;
for (Iterator it = collection.iterator(); it.hasNext();) {
Object obj = it.next();
if (typeToUse.isInstance(obj)) {
if (value != null) {
throw new IllegalArgumentException("More than one value of type [" + typeToUse.getName() + "] found");
}
value = obj;
}
}
return value;
}
/**
* Return true if the supplied Collection is null
* or empty. Otherwise, return false.
* @param collection the Collection to check
* @return whether the given Collection is empty
*/
public static boolean isEmpty(Collection collection) {
return (collection == null || collection.isEmpty());
}
/**
* Return true if the supplied Map is null
* or empty. Otherwise, return false.
* @param map the Map to check
* @return whether the given Map is empty
*/
public static boolean isEmpty(Map map) {
return (map == null || map.isEmpty());
}
/**
* Return the first element in 'candidates' that is contained in
* 'source'. If no element in 'candidates' is present in
* 'source' returns null. Iteration order is
* {@link Collection} implementation specific.
* @param source the source Collection
* @param candidates the candidates to search for
* @return the first present object, or null if not found
*/
public static Object findFirstMatch(Collection source, Collection candidates) {
if (isEmpty(source) || isEmpty(candidates)) {
return null;
}
for (Iterator it = candidates.iterator(); it.hasNext();) {
Object candidate = it.next();
if (source.contains(candidate)) {
return candidate;
}
}
return null;
}
/**
* Determine whether the given Collection only contains a single unique object.
* @param collection the Collection to check
* @return true if the collection contains a single reference or
* multiple references to the same instance, false else
*/
public static boolean hasUniqueObject(Collection collection) {
if (isEmpty(collection)) {
return false;
}
boolean hasCandidate = false;
Object candidate = null;
for (Iterator it = collection.iterator(); it.hasNext();) {
Object elem = it.next();
if (!hasCandidate) {
hasCandidate = true;
candidate = elem;
}
else if (candidate != elem) {
return false;
}
}
return true;
}
}