Implements an java.util.Iterator over any array : Iterator « Collections « Java Tutorial

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Java Tutorial » Collections » Iterator 




/*
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 *  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,
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 */


import java.lang.reflect.Array;
import java.util.NoSuchElementException;

/** 
 * 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 org.apache.commons.collections.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.
 *
 @since Commons Collections 1.0
 @version $Revision$ $Date$
 *
 @author James Strachan
 @author Mauricio S. Moura
 @author Michael A. Smith
 @author Neil O'Toole
 @author Stephen Colebourne
 */
public class ArrayIterator implements java.util.Iterator {

    /** The array to iterate over */    
    protected Object array;
    /** The end index to loop to */
  protected int endIndex = 0;
    /** The current iterator index */
  protected int index = 0;
    
   
    /**
     * Constructs an ArrayIterator that will iterate over the values in the
     * specified array.
     *
     @param array the array to iterate over.
     @throws IllegalArgumentException if <code>array</code> is not an array.
     @throws NullPointerException if <code>array</code> is <code>null</code>
     */
    public ArrayIterator(final Object array) {
        setArray(array);
    }

    /**
     * Checks whether the index is valid or not.
     
     @param bound  the index to check
     @param type  the index type (for error messages)
     @throws IndexOutOfBoundsException if the index is invalid
     */
    protected void checkBound(final int bound, final String type ) {
        if (bound > this.endIndex) {
            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
     */
    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
     */
    public Object next() {
        if (hasNext() == false) {
            throw new NoSuchElementException();
        }
        return Array.get(array, index++);
    }

    /**
     * Throws {@link UnsupportedOperationException}.
     *
     @throws UnsupportedOperationException always
     */
    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, or <code>null</code> if
     *  the no-arg constructor was used and {@link #setArray(Object)} has never
     *  been called with a valid array.
     */
    public Object getArray() {
        return array;
    }
    
    /**
     * Sets the array that the ArrayIterator should iterate over.
     
     * If an array has previously been set (using the single-arg constructor
     * or this method) then that array is discarded in favour of this one.
     * Iteration is restarted at the start of the new array.
     * Although this can be used to reset iteration, the {@link #clear()} method
     * is a more effective choice.
     *
     @param array the array that the iterator should iterate over.
     @throws IllegalArgumentException if <code>array</code> is not an array.
     @throws NullPointerException if <code>array</code> is <code>null</code>
     */
    private void setArray(final Object array) {
        // Array.getLength throws IllegalArgumentException if the object is not
        // an array or NullPointerException if the object is null.  This call
        // is made before saving the array and resetting the index so that the
        // array iterator remains in a consistent state if the argument is not
        // an array or is null.
        this.endIndex = Array.getLength(array);
        this.array = array;
        this.index = 0;
    }

}














9.37.Iterator
9.37.1.Use Iterator to loop through ArrayList
9.37.2.Use Iterator to loop through the HashMap class
9.37.3.Iterate through a Collection using Java Iterator
9.37.4.Traverse through ArrayList in forward direction using Java ListIterator
9.37.5.Traverse through ArrayList in reverse direction using Java ListIterator
9.37.6.Iterate a Collection and remove an item (Exception, wrong version)
9.37.7.Remove an element from Collection using Java Iterator
9.37.8.Iterator from LinkedList
9.37.9.Iterate through elements of Java LinkedList using Iterator
9.37.10.An Iterator that wraps a number of Iterators
9.37.11.Array Iterator
9.37.12.Create singleton Iterator
9.37.13.Cyclic Iteration
9.37.14.Iterator Union of Iterators
9.37.15.Iterator Utils
9.37.16.Iterator class for sparse values in an array.
9.37.17.Iterator class for values contained in an array range.
9.37.18.Sorted Iterator
9.37.19.Treat an Iterator as an Iterable
9.37.20.An Iterator that returns the elements of a specified array, or other iterators etc.
9.37.21.An Iterator wrapper for an Enumeration.
9.37.22.An Iterator wrapper for an Object[], allow us to deal with all array like structures in a consistent manner.
9.37.23.An iterator that breaks text into lines. The result is equal to BufferedReader.readLine().
9.37.24.Gets the child of the specified element having the specified unique name
9.37.25.Implements an java.util.Iterator over any array
9.37.26.Protects an given iterator by preventing calls to remove().
9.37.27.Returns an iterator over the children of the given element with the given tag name
9.37.28.Use an Iterator to cycle through a collection in the forward direction.
9.37.29.This constructs an Iterator over each day in a date range defined by a focus date and range style.
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