1 /* 2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 8 * - Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 11 * - Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * - Neither the name of Oracle nor the names of its 16 * contributors may be used to endorse or promote products derived 17 * from this software without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS 20 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 21 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 23 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 24 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 25 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 26 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 27 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 28 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 29 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 import java.util.Iterator; 33 import java.util.NoSuchElementException; 34 35 /** 36 * The code sample illustrates the usage of default methods in the JDK 8. Most 37 * implementations of {@link Iterator} don't provide a useful 38 * {@link Iterator#remove()} method, however, 39 * they still have to implement this method to throw 40 * an UnsupportedOperationException. With the default method, the same 41 * default behavior in interface Iterator itself can be provided. 42 */ 43 public class ArrayIterator { 44 45 /** Close the constructor because ArrayIterator is part of the utility 46 * class. 47 */ ArrayIterator()48 protected ArrayIterator() { 49 throw new UnsupportedOperationException(); 50 } 51 52 /** 53 * Returns an iterator that goes over the elements in the array. 54 * 55 * @param <E> type of an array element 56 * @param array source array to iterate over it 57 * @return an iterator that goes over the elements in the array 58 */ iterator(final E[] array)59 public static <E> Iterator<E> iterator(final E[] array) { 60 return new Iterator<E>() { 61 /** 62 * Index of the current position 63 * 64 */ 65 private int index = 0; 66 67 /** 68 * Returns the next element in the iteration 69 * 70 * @return the next element in the iteration 71 * @throws NoSuchElementException if the iteration has no more 72 * elements 73 */ 74 @Override 75 public boolean hasNext() { 76 return (index < array.length); 77 } 78 79 /** 80 * Returns {@code true} if the iteration has more elements. (In 81 * other words, returns {@code true} if {@link #next} returns 82 * an element, rather than throwing an exception.) 83 * 84 * @return {@code true} if the iteration has more elements 85 */ 86 @Override 87 public E next() { 88 if (!hasNext()) { 89 throw new NoSuchElementException(); 90 } 91 return array[index++]; 92 } 93 94 /** 95 * This method does not need to be overwritten in JDK 8. 96 */ 97 //@Override 98 //public void remove() { 99 // throw UnsupportedOperationException( 100 // "Arrays don't support remove.") 101 //} 102 }; 103 } 104 105 /** 106 * Sample usage of the ArrayIterator 107 * 108 * @param args command-line arguments 109 */ main(final String[] args)110 public static void main(final String[] args) { 111 Iterator<String> it = ArrayIterator.iterator( 112 new String[]{"one", "two", "three"}); 113 114 while (it.hasNext()) { 115 System.out.println(it.next()); 116 } 117 } 118 } 119