| // Copyright 2014 The Bazel Authors. All rights reserved. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| package com.google.devtools.build.lib.collect.nestedset; |
| |
| import com.google.common.collect.ImmutableList; |
| import com.google.common.collect.ImmutableSet; |
| |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.Objects; |
| import java.util.Set; |
| |
| import javax.annotation.Nullable; |
| |
| /** |
| * An empty nested set. |
| */ |
| final class EmptyNestedSet<E> extends NestedSet<E> { |
| private static final NestedSet[] EMPTY_NESTED_SET = new NestedSet[0]; |
| private static final Object[] EMPTY_ELEMENTS = new Object[0]; |
| private final Order order; |
| |
| EmptyNestedSet(Order type) { |
| this.order = type; |
| } |
| |
| @Override |
| public Iterator<E> iterator() { |
| return ImmutableList.<E>of().iterator(); |
| } |
| |
| @Override |
| Object[] directMembers() { |
| return EMPTY_ELEMENTS; |
| } |
| |
| @Override |
| NestedSet[] transitiveSets() { |
| return EMPTY_NESTED_SET; |
| } |
| |
| @Override |
| public boolean isEmpty() { |
| return true; |
| } |
| |
| @Override |
| public List<E> toList() { |
| return ImmutableList.of(); |
| } |
| |
| @Override |
| public Set<E> toSet() { |
| return ImmutableSet.of(); |
| } |
| |
| @Override |
| public String toString() { |
| return "{}"; |
| } |
| |
| @Override |
| public Order getOrder() { |
| return order; |
| } |
| |
| @Override |
| public boolean shallowEquals(@Nullable NestedSet<? extends E> other) { |
| return other != null && getOrder() == other.getOrder() && other.isEmpty(); |
| } |
| |
| @Override |
| public int shallowHashCode() { |
| return Objects.hashCode(getOrder()); |
| } |
| } |