org.apache.commons.collections4.iterators.EnumerationIterator Maven / Gradle / Ivy
Show all versions of commons-collections4 Show documentation
/*
* 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.
*/
package org.apache.commons.collections4.iterators;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
/**
* Adapter to make {@link Enumeration Enumeration} instances appear
* to be {@link Iterator Iterator} instances.
*
* @since 1.0
*/
public class EnumerationIterator implements Iterator {
/** The collection to remove elements from */
private final Collection collection;
/** The enumeration being converted */
private Enumeration enumeration;
/** The last object retrieved */
private E last;
// Constructors
//-----------------------------------------------------------------------
/**
* Constructs a new EnumerationIterator that will not
* function until {@link #setEnumeration(Enumeration)} is called.
*/
public EnumerationIterator() {
this(null, null);
}
/**
* Constructs a new EnumerationIterator that provides
* an iterator view of the given enumeration.
*
* @param enumeration the enumeration to use
*/
public EnumerationIterator(final Enumeration enumeration) {
this(enumeration, null);
}
/**
* Constructs a new EnumerationIterator that will remove
* elements from the specified collection.
*
* @param enumeration the enumeration to use
* @param collection the collection to remove elements from
*/
public EnumerationIterator(final Enumeration enumeration, final Collection collection) {
super();
this.enumeration = enumeration;
this.collection = collection;
this.last = null;
}
// Iterator interface
//-----------------------------------------------------------------------
/**
* Returns true if the underlying enumeration has more elements.
*
* @return true if the underlying enumeration has more elements
* @throws NullPointerException if the underlying enumeration is null
*/
@Override
public boolean hasNext() {
return enumeration.hasMoreElements();
}
/**
* Returns the next object from the enumeration.
*
* @return the next object from the enumeration
* @throws NullPointerException if the enumeration is null
*/
@Override
public E next() {
last = enumeration.nextElement();
return last;
}
/**
* Removes the last retrieved element if a collection is attached.
*
* Functions if an associated Collection is known.
* If so, the first occurrence of the last returned object from this
* iterator will be removed from the collection.
*
* @throws IllegalStateException next() not called.
* @throws UnsupportedOperationException if no associated collection
*/
@Override
public void remove() {
if (collection != null) {
if (last != null) {
collection.remove(last);
} else {
throw new IllegalStateException("next() must have been called for remove() to function");
}
} else {
throw new UnsupportedOperationException("No Collection associated with this Iterator");
}
}
// Properties
//-----------------------------------------------------------------------
/**
* Returns the underlying enumeration.
*
* @return the underlying enumeration
*/
public Enumeration getEnumeration() {
return enumeration;
}
/**
* Sets the underlying enumeration.
*
* @param enumeration the new underlying enumeration
*/
public void setEnumeration(final Enumeration enumeration) {
this.enumeration = enumeration;
}
}