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XMLTooling-J is a low-level library that may be used to construct libraries that allow developers to work with XML in a Java beans manner.
/*
* Licensed to the University Corporation for Advanced Internet Development,
* Inc. (UCAID) under one or more contributor license agreements. See the
* NOTICE file distributed with this work for additional information regarding
* copyright ownership. The UCAID 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.opensaml.xml.util;
import java.util.AbstractSet;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
/**
* Set implementation which provides indexed access to set members via their class,
* and which allows only one instance of a given class to be present in the set. Null
* members are not allowed.
*
* @param the type of object stored by this class
*/
public class ClassIndexedSet extends AbstractSet implements Set {
/** Storage for set members. */
private HashSet set;
/** Storage for index of class -> member. */
private HashMap, T> index;
/**
* Constructor.
*
*/
public ClassIndexedSet() {
set = new HashSet();
index = new HashMap, T>();
}
/** {@inheritDoc} */
public boolean add(T o) {
return add(o, false);
}
/**
* Add member to set, optionally replacing any existing instance of the
* same class.
*
* @param o the object to add
* @param replace flag indicating whether to replace an existing class type
* @return true if object was added
* @throws IllegalArgumentException if set already contained an instance of the object's class
* and replacement was specified as false
* @throws NullPointerException if the object to add was null
*/
@SuppressWarnings("unchecked")
public boolean add(T o, boolean replace) throws NullPointerException, IllegalArgumentException {
if (o == null) {
throw new NullPointerException("Null elements are not allowed");
}
boolean replacing = false;
Class indexClass = getIndexClass(o);
T existing = get(indexClass);
if (existing != null) {
replacing = true;
if (replace) {
remove(existing);
} else {
throw new IllegalArgumentException("Set already contains a member of index class "
+ indexClass.getName());
}
}
index.put(indexClass, o);
set.add(o);
return replacing;
}
/** {@inheritDoc} */
public void clear() {
set.clear();
index.clear();
}
/** {@inheritDoc} */
@SuppressWarnings("unchecked")
public boolean remove(Object o) {
if (set.contains(o)) {
removeFromIndex((T) o);
set.remove(o);
return true;
}
return false;
}
/** {@inheritDoc} */
public Iterator iterator() {
return new ClassIndexedSetIterator(this, set.iterator());
}
/** {@inheritDoc} */
public int size() {
return set.size();
}
/**
* Check whether set contains an instance of the specified class.
*
* @param clazz the class to check
* @return true if set contains an instance of the specified class, false otherwise
*/
public boolean contains(Class clazz) {
return get(clazz)!=null;
}
/**
* Get the set element specified by the class parameter.
* @param generic parameter which eliminates need for casting by the caller
* @param clazz the class to whose instance is to be retrieved
* @return the element whose class is of the type specified, or null
*
*/
@SuppressWarnings("unchecked")
public X get(Class clazz) {
return (X) index.get(clazz);
}
/**
* Get the index class of the specified object. Subclasses may override to use
* a class index other than the main runtime class of the object.
*
* @param o the object whose class index to determine
* @return the class index value associated with the object instance
*/
@SuppressWarnings("unchecked")
protected Class getIndexClass(Object o) {
return (Class) o.getClass();
}
/**
* Remove the specified object from the index.
*
* @param o the object to remove
*/
private void removeFromIndex(T o) {
index.remove(getIndexClass(o));
}
/**
* Iterator for set implementation {@link ClassIndexedSet}.
*
*/
protected class ClassIndexedSetIterator implements Iterator {
/** The set instance over which this instance is an iterator. */
private ClassIndexedSet set;
/** The iterator for the owner's underlying storage. */
private Iterator iterator;
/** Flag which tracks whether next() has been called at least once. */
private boolean nextCalled;
/** Flag which tracks whether remove can currently be called. */
private boolean removeStateValid;;
/** The element most recently returned by next(), and the target for any subsequent
* remove() operation. */
private T current;
/**
* Constructor.
*
* @param parentSet the {@link ClassIndexedSet} over which this instance is an iterator
* @param parentIterator the iterator for the parent's underlying storage
*/
protected ClassIndexedSetIterator(ClassIndexedSet parentSet, Iterator parentIterator) {
set = parentSet;
iterator = parentIterator;
current = null;
nextCalled = false;
removeStateValid = false;
}
/** {@inheritDoc} */
public boolean hasNext() {
return iterator.hasNext();
}
/** {@inheritDoc} */
public T next() {
current = iterator.next();
nextCalled = true;
removeStateValid = true;
return current;
}
/** {@inheritDoc} */
public void remove() {
if (! nextCalled) {
throw new IllegalStateException("remove() was called before calling next()");
}
if (! removeStateValid) {
throw new IllegalStateException("remove() has already been called since the last call to next()");
}
iterator.remove();
set.removeFromIndex(current);
removeStateValid = false;
}
}
}
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