1/* 2 * Copyright (C) 2011 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 5 * in compliance with the License. You may obtain a copy of the License at 6 * 7 * http://www.apache.org/licenses/LICENSE-2.0 8 * 9 * Unless required by applicable law or agreed to in writing, software distributed under the 10 * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either 11 * express or implied. See the License for the specific language governing permissions and 12 * limitations under the License. 13 */ 14 15package com.google.common.collect; 16 17import static com.google.common.base.Preconditions.checkNotNull; 18 19import com.google.common.annotations.GwtCompatible; 20 21import java.util.Comparator; 22import java.util.SortedSet; 23 24/** 25 * Utilities for dealing with sorted collections of all types. 26 * 27 * @author Louis Wasserman 28 */ 29@GwtCompatible 30final class SortedIterables { 31 private SortedIterables() {} 32 33 /** 34 * Returns {@code true} if {@code elements} is a sorted collection using an ordering equivalent 35 * to {@code comparator}. 36 */ 37 public static boolean hasSameComparator(Comparator<?> comparator, Iterable<?> elements) { 38 checkNotNull(comparator); 39 checkNotNull(elements); 40 Comparator<?> comparator2; 41 if (elements instanceof SortedSet) { 42 comparator2 = comparator((SortedSet<?>) elements); 43 } else if (elements instanceof SortedIterable) { 44 comparator2 = ((SortedIterable<?>) elements).comparator(); 45 } else { 46 return false; 47 } 48 return comparator.equals(comparator2); 49 } 50 51 @SuppressWarnings("unchecked") 52 // if sortedSet.comparator() is null, the set must be naturally ordered 53 public static <E> Comparator<? super E> comparator(SortedSet<E> sortedSet) { 54 Comparator<? super E> result = sortedSet.comparator(); 55 if (result == null) { 56 result = (Comparator<? super E>) Ordering.natural(); 57 } 58 return result; 59 } 60} 61