org.springframework.webflow.core.collection.CollectionUtils Maven / Gradle / Ivy
/*
* Copyright 2002-2006 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.
*/
package org.springframework.webflow.core.collection;
import java.io.Serializable;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
/**
* A utility class for working with attribute and parameter collections used by
* Spring Web FLow.
*
* @author Keith Donald
* @author Erwin Vervaet
*/
public class CollectionUtils {
/**
* The shared, singleton empty iterator instance.
*/
public static final Iterator EMPTY_ITERATOR = new EmptyIterator();
/**
* The shared, singleton empty attribute map instance.
*/
public static final AttributeMap EMPTY_ATTRIBUTE_MAP = new LocalAttributeMap(Collections.EMPTY_MAP);
/**
* Private constructor to avoid instantiation.
*/
private CollectionUtils() {
}
/**
* Factory method that adapts an enumeration to an iterator.
* @param enumeration the enumeration
* @return the iterator
*/
public static Iterator toIterator(Enumeration enumeration) {
return new EnumerationIterator(enumeration);
}
/**
* Factory method that returns a unmodifiable attribute map with a single
* entry.
* @param attributeName the attribute name
* @param attributeValue the attribute value
* @return the unmodifiable map with a single element
*/
public static AttributeMap singleEntryMap(String attributeName, Object attributeValue) {
return new LocalAttributeMap(attributeName, attributeValue);
}
/**
* Add all given objects to given target list. No duplicates will be added.
* The contains() method of the given target list will be used to determine
* whether or not an object is already in the list.
* @param target the collection to which to objects will be added
* @param objects the objects to add
* @return whether or not the target collection changed
*/
public static boolean addAllNoDuplicates(List target, Object[] objects) {
if (objects == null || objects.length == 0) {
return false;
}
else {
boolean changed = false;
for (int i = 0; i < objects.length; i++) {
if (!target.contains(objects[i])) {
target.add(objects[i]);
changed = true;
}
}
return changed;
}
}
/**
* Iterator iterating over no elements (hasNext() always returns false).
*/
private static class EmptyIterator implements Iterator, Serializable {
private EmptyIterator() {
}
public boolean hasNext() {
return false;
}
public Object next() {
throw new UnsupportedOperationException("There are no elements");
}
public void remove() {
throw new UnsupportedOperationException("There are no elements");
}
}
/**
* Iterator wrapping an Enumeration.
*/
private static class EnumerationIterator implements Iterator {
private Enumeration enumeration;
public EnumerationIterator(Enumeration enumeration) {
this.enumeration = enumeration;
}
public boolean hasNext() {
return enumeration.hasMoreElements();
}
public Object next() {
return enumeration.nextElement();
}
public void remove() throws UnsupportedOperationException {
throw new UnsupportedOperationException("Not supported");
}
}
}