1/* 2 * Copyright (c) 2017, 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23package org.graalvm.compiler.core.common.util; 24 25import java.util.AbstractList; 26import java.util.List; 27import java.util.RandomAccess; 28 29/** 30 * A {@code ReversedList} is a view on an other list with the elements in reverse order. 31 * 32 * This implementation is made for {@link RandomAccess} lists. 33 */ 34public class ReversedList<T> extends AbstractList<T> implements RandomAccess { 35 private final List<T> original; 36 37 public ReversedList(List<T> original) { 38 assert original instanceof RandomAccess; 39 this.original = original; 40 } 41 42 @Override 43 public T get(int index) { 44 return original.get(original.size() - index - 1); 45 } 46 47 @Override 48 public int size() { 49 return original.size(); 50 } 51 52 /** 53 * Creates a list that is a view on {@code list} in reverse order. 54 */ 55 public static <T> ReversedList<T> reversed(List<T> list) { 56 return new ReversedList<>(list); 57 } 58} 59