ObjectArrayListIterator.java
/*
* 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.ResettableListIterator;
/**
* Implements a {@link java.util.ListIterator} over an array of objects.
* <p>
* This iterator does not support {@link #add} or {@link #remove}, as the object array
* cannot be structurally modified. The {@link #set} method is supported however.
* <p>
* The iterator implements a {@link #reset} method, allowing the reset of the iterator
* back to the start if required.
*
* @param <E> the type of elements returned by this iterator.
* @see org.apache.commons.collections4.iterators.ObjectArrayIterator
* @see java.util.Iterator
* @see java.util.ListIterator
*
* @since 3.0
*/
public class ObjectArrayListIterator<E> extends ObjectArrayIterator<E>
implements ResettableListIterator<E> {
/**
* Holds the index of the last item returned by a call to {@code next()}
* or {@code previous()}. This is set to {@code -1} if neither method
* has yet been invoked. {@code lastItemIndex} is used to implement the
* {@link #set} method.
*/
private int lastItemIndex = -1;
/**
* Constructs an ObjectArrayListIterator that will iterate over the values in the
* specified array.
*
* @param array the array to iterate over
* @throws NullPointerException if {@code array} is {@code null}
*/
public ObjectArrayListIterator(final E... array) {
super(array);
}
/**
* Constructs an ObjectArrayListIterator that will iterate over the values in the
* specified array from a specific start index.
*
* @param array the array to iterate over
* @param start the index to start iterating at
* @throws NullPointerException if {@code array} is {@code null}
* @throws IndexOutOfBoundsException if the start index is out of bounds
*/
public ObjectArrayListIterator(final E[] array, final int start) {
super(array, start);
}
/**
* Constructs an ObjectArrayListIterator that will iterate over a range of values
* in the specified array.
*
* @param array the array to iterate over
* @param start the index to start iterating at
* @param end the index (exclusive) to finish iterating at
* @throws IndexOutOfBoundsException if the start or end index is out of bounds
* @throws IllegalArgumentException if end index is before the start
* @throws NullPointerException if {@code array} is {@code null}
*/
public ObjectArrayListIterator(final E[] array, final int start, final int end) {
super(array, start, end);
}
/**
* This iterator does not support modification of its backing array's size, and so will
* always throw an {@link UnsupportedOperationException} when this method is invoked.
*
* @param obj the object to add
* @throws UnsupportedOperationException always thrown.
*/
@Override
public void add(final E obj) {
throw new UnsupportedOperationException("add() method is not supported");
}
/**
* Returns true if there are previous elements to return from the array.
*
* @return true if there is a previous element to return
*/
@Override
public boolean hasPrevious() {
return this.index > getStartIndex();
}
/**
* Gets the next element from the array.
*
* @return the next element
* @throws NoSuchElementException if there is no next element
*/
@Override
public E next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
this.lastItemIndex = this.index;
return this.array[this.index++];
}
/**
* Gets the next index to be retrieved.
*
* @return the index of the item to be retrieved next
*/
@Override
public int nextIndex() {
return this.index - getStartIndex();
}
/**
* Gets the previous element from the array.
*
* @return the previous element
* @throws NoSuchElementException if there is no previous element
*/
@Override
public E previous() {
if (!hasPrevious()) {
throw new NoSuchElementException();
}
this.lastItemIndex = --this.index;
return this.array[this.index];
}
/**
* Gets the index of the item to be retrieved if {@link #previous()} is called.
*
* @return the index of the item to be retrieved next
*/
@Override
public int previousIndex() {
return this.index - getStartIndex() - 1;
}
/**
* Resets the iterator back to the start index.
*/
@Override
public void reset() {
super.reset();
this.lastItemIndex = -1;
}
/**
* Sets the element under the cursor.
* <p>
* This method sets the element that was returned by the last call
* to {@link #next()} of {@link #previous()}.
*
* <b>Note:</b> {@link java.util.ListIterator} implementations that support {@code add()}
* and {@code remove()} only allow {@code set()} to be called once per call
* to {@code next()} or {@code previous} (see the {@link java.util.ListIterator}
* Javadoc for more details). Since this implementation does not support
* {@code add()} or {@code remove()}, {@code set()} may be
* called as often as desired.
*
* @param obj the object to set into the array
* @throws IllegalStateException if next() has not yet been called.
* @throws ClassCastException if the object type is unsuitable for the array
*/
@Override
public void set(final E obj) {
if (this.lastItemIndex == -1) {
throw new IllegalStateException("must call next() or previous() before a call to set()");
}
this.array[this.lastItemIndex] = obj;
}
}