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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.
*/
package org.apache.commons.collections4.iterators;
import java.util.NoSuchElementException;
import org.apache.commons.collections4.ResettableIterator;
/**
* SingletonIterator is an {@link java.util.Iterator} over a single
* object instance.
*
* @since 2.0
*/
public class SingletonIterator
implements ResettableIterator {
/** Whether remove is allowed */
private final boolean removeAllowed;
/** Is the cursor before the first element */
private boolean beforeFirst = true;
/** Has the element been removed */
private boolean removed = false;
/** The object */
private E object;
/**
* Constructs a new SingletonIterator where remove
* is a permitted operation.
*
* @param object the single object to return from the iterator
*/
public SingletonIterator(final E object) {
this(object, true);
}
/**
* Constructs a new SingletonIterator optionally choosing if
* remove is a permitted operation.
*
* @param object the single object to return from the iterator
* @param removeAllowed true if remove is allowed
* @since 3.1
*/
public SingletonIterator(final E object, final boolean removeAllowed) {
super();
this.object = object;
this.removeAllowed = removeAllowed;
}
//-----------------------------------------------------------------------
/**
* Is another object available from the iterator?
*
* This returns true if the single object hasn't been returned yet.
*
* @return true if the single object hasn't been returned yet
*/
@Override
public boolean hasNext() {
return beforeFirst && !removed;
}
/**
* Get the next object from the iterator.
*
* This returns the single object if it hasn't been returned yet.
*
* @return the single object
* @throws NoSuchElementException if the single object has already
* been returned
*/
@Override
public E next() {
if (!beforeFirst || removed) {
throw new NoSuchElementException();
}
beforeFirst = false;
return object;
}
/**
* Remove the object from this iterator.
*
* @throws IllegalStateException if the {@code next} method has not
* yet been called, or the {@code remove} method has already
* been called after the last call to the {@code next}
* method.
* @throws UnsupportedOperationException if remove is not supported
*/
@Override
public void remove() {
if (removeAllowed) {
if (removed || beforeFirst) {
throw new IllegalStateException();
}
object = null;
removed = true;
} else {
throw new UnsupportedOperationException();
}
}
/**
* Reset the iterator to the start.
*/
@Override
public void reset() {
beforeFirst = true;
}
}