1 /* 2 * Copyright (c) 2013, 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 Iterator don’t provide a useful remove() method, however, 38 * they still have to implement this method to throw 39 * an UnsupportedOperationException. With the default method, the same 40 * default behavior in interface Iterator itself can be provided. 41 * 42 * @author Taras Ledkov 43 */ 44 public class ArrayIterator { 45 46 /** Close the constructor because ArrayIterator is part of the utility 47 * class. 48 */ 49 protected ArrayIterator() { 50 throw new UnsupportedOperationException(); 51 } 52 53 /** 54 * Returns an iterator that goes over the elements in the array. 55 * 56 * @param <E> type of an array element 57 * @param array source array to iterate over it 58 * @return an iterator that goes over the elements in the array 59 */ 60 public static <E> Iterator<E> iterator(final E[] array) { 61 return new Iterator<E>() { 62 /** 63 * Initial array 64 * 65 */ 66 private final E[] srcArray = array; 67 68 /** 69 * Index of the current position 70 * 71 */ 72 private int index = 0; 73 74 /** 75 * Returns the next element in the iteration 76 * 77 * @return the next element in the iteration 78 * @throws NoSuchElementException if the iteration has no more 79 * elements 80 */ 81 @Override 82 public boolean hasNext() { 83 return (index < srcArray.length); 84 } 85 86 /** 87 * Returns {@code true} if the iteration has more elements. (In 88 * other words, returns {@code true} if {@link #next} returns 89 * an element, rather than throwing an exception.) 90 * 91 * @return {@code true} if the iteration has more elements 92 */ 93 @Override 94 public E next() { 95 if (!hasNext()) { 96 throw new NoSuchElementException(); 97 } 98 return srcArray[index++]; 99 } 100 101 /** 102 * This method does not need to be overwritten in JDK 8. 103 */ 104 //@Override 105 //public void remove() { 106 // throw UnsupportedOperationException( 107 // "Arrays don't support remove.") 108 //} 109 }; 110 } 111 112 /** 113 * Sample usage of the ArrayIterator 114 * 115 * @param args command-line arguments 116 */ 117 public static void main(final String[] args) { 118 Iterator<String> it = ArrayIterator.iterator( 119 new String[]{"one", "two", "three"}); 120 121 while (it.hasNext()) { 122 System.out.println(it.next()); 123 } 124 } 125 }