1 /* 2 * Copyright (C) 2007 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.collect; 18 19 import com.google.common.annotations.GwtCompatible; 20 import java.io.Serializable; 21 import javax.annotation.CheckForNull; 22 import org.checkerframework.checker.nullness.qual.Nullable; 23 24 /** An ordering that treats {@code null} as greater than all other values. */ 25 @GwtCompatible(serializable = true) 26 @ElementTypesAreNonnullByDefault 27 final class NullsLastOrdering<T extends @Nullable Object> extends Ordering<@Nullable T> 28 implements Serializable { 29 final Ordering<? super T> ordering; 30 NullsLastOrdering(Ordering<? super T> ordering)31 NullsLastOrdering(Ordering<? super T> ordering) { 32 this.ordering = ordering; 33 } 34 35 @Override compare(@heckForNull T left, @CheckForNull T right)36 public int compare(@CheckForNull T left, @CheckForNull T right) { 37 if (left == right) { 38 return 0; 39 } 40 if (left == null) { 41 return LEFT_IS_GREATER; 42 } 43 if (right == null) { 44 return RIGHT_IS_GREATER; 45 } 46 return ordering.compare(left, right); 47 } 48 49 @Override 50 @SuppressWarnings("nullness") // should be safe, but not sure if we can avoid the warning reverse()51 public <S extends @Nullable T> Ordering<S> reverse() { 52 // ordering.reverse() might be optimized, so let it do its thing 53 return ordering.reverse().nullsFirst(); 54 } 55 56 @Override nullsFirst()57 public <S extends T> Ordering<@Nullable S> nullsFirst() { 58 return ordering.<S>nullsFirst(); 59 } 60 61 @SuppressWarnings("unchecked") // still need the right way to explain this 62 @Override nullsLast()63 public <S extends T> Ordering<@Nullable S> nullsLast() { 64 return (Ordering<@Nullable S>) this; 65 } 66 67 @Override equals(@heckForNull Object object)68 public boolean equals(@CheckForNull Object object) { 69 if (object == this) { 70 return true; 71 } 72 if (object instanceof NullsLastOrdering) { 73 NullsLastOrdering<?> that = (NullsLastOrdering<?>) object; 74 return this.ordering.equals(that.ordering); 75 } 76 return false; 77 } 78 79 @Override hashCode()80 public int hashCode() { 81 return ordering.hashCode() ^ -921210296; // meaningless 82 } 83 84 @Override toString()85 public String toString() { 86 return ordering + ".nullsLast()"; 87 } 88 89 private static final long serialVersionUID = 0; 90 } 91