com.feilong.lib.collection4.iterators.ArrayIterator Maven / Gradle / Ivy
Show all versions of feilong 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 com.feilong.lib.collection4.iterators;
import java.lang.reflect.Array;
import java.util.NoSuchElementException;
import org.apache.commons.collections4.ResettableIterator;
/**
* Implements an {@link java.util.Iterator Iterator} over any array.
*
* The array can be either an array of object or of primitives. If you know
* that you have an object array, the
* {@link com.feilong.lib.collection4.iterators.ObjectArrayIterator ObjectArrayIterator}
* class is a better choice, as it will perform better.
*
* The iterator implements a {@link #reset} method, allowing the reset of
* the iterator back to the start if required.
*
* @param
* the type of elements returned by this iterator
* @since 1.0
*/
public class ArrayIterator implements ResettableIterator{
/** The array to iterate over */
final Object array;
/** The start index to loop from */
final int startIndex;
/** The end index to loop to */
final int endIndex;
/** The current iterator index */
int index = 0;
// Constructors
// ----------------------------------------------------------------------
/**
* Constructs an ArrayIterator that will iterate over the values in the
* specified array.
*
* @param array
* the array to iterate over.
* @throws IllegalArgumentException
* if array is not an array.
* @throws NullPointerException
* if array is null
*/
public ArrayIterator(final Object array){
this(array, 0);
}
/**
* Constructs an ArrayIterator that will iterate over the values in the
* specified array from a specific start index.
*
* @param array
* the array to iterate over.
* @param startIndex
* the index to start iterating at.
* @throws IllegalArgumentException
* if array is not an array.
* @throws NullPointerException
* if array is null
* @throws IndexOutOfBoundsException
* if the index is invalid
*/
public ArrayIterator(final Object array, final int startIndex){
this(array, startIndex, Array.getLength(array));
}
/**
* Construct an ArrayIterator that will iterate over a range of values
* in the specified array.
*
* @param array
* the array to iterate over.
* @param startIndex
* the index to start iterating at.
* @param endIndex
* the index to finish iterating at.
* @throws IllegalArgumentException
* if array is not an array.
* @throws NullPointerException
* if array is null
* @throws IndexOutOfBoundsException
* if either index is invalid
*/
public ArrayIterator(final Object array, final int startIndex, final int endIndex){
super();
this.array = array;
this.startIndex = startIndex;
this.endIndex = endIndex;
this.index = startIndex;
final int len = Array.getLength(array);
checkBound(startIndex, len, "start");
checkBound(endIndex, len, "end");
if (endIndex < startIndex){
throw new IllegalArgumentException("End index must not be less than start index.");
}
}
/**
* Checks whether the index is valid or not.
*
* @param bound
* the index to check
* @param len
* the length of the array
* @param type
* the index type (for error messages)
* @throws IndexOutOfBoundsException
* if the index is invalid
*/
protected void checkBound(final int bound,final int len,final String type){
if (bound > len){
throw new ArrayIndexOutOfBoundsException("Attempt to make an ArrayIterator that " + type + "s beyond the end of the array. ");
}
if (bound < 0){
throw new ArrayIndexOutOfBoundsException("Attempt to make an ArrayIterator that " + type + "s before the start of the array. ");
}
}
// Iterator interface
//-----------------------------------------------------------------------
/**
* Returns true if there are more elements to return from the array.
*
* @return true if there is a next element to return
*/
@Override
public boolean hasNext(){
return index < endIndex;
}
/**
* Returns the next element in the array.
*
* @return the next element in the array
* @throws NoSuchElementException
* if all the elements in the array
* have already been returned
*/
@Override
@SuppressWarnings("unchecked")
public E next(){
if (hasNext() == false){
throw new NoSuchElementException();
}
return (E) Array.get(array, index++);
}
/**
* Throws {@link UnsupportedOperationException}.
*
* @throws UnsupportedOperationException
* always
*/
@Override
public void remove(){
throw new UnsupportedOperationException("remove() method is not supported");
}
// Properties
//-----------------------------------------------------------------------
/**
* Gets the array that this iterator is iterating over.
*
* @return the array this iterator iterates over.
*/
public Object getArray(){
return array;
}
/**
* Gets the start index to loop from.
*
* @return the start index
* @since 4.0
*/
public int getStartIndex(){
return this.startIndex;
}
/**
* Gets the end index to loop to.
*
* @return the end index
* @since 4.0
*/
public int getEndIndex(){
return this.endIndex;
}
/**
* Resets the iterator back to the start index.
*/
@Override
public void reset(){
this.index = this.startIndex;
}
}