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;
18import static com.google.common.base.Preconditions.checkState;
19
20import com.google.common.annotations.GwtCompatible;
21
22import javax.annotation.Nullable;
23
24/**
25 * A path to a node in a binary search tree, originating at the root.
26 *
27 * @author Louis Wasserman
28 * @param <N> The type of nodes in this binary search tree.
29 * @param <P> This path type, and the path type of all suffix paths.
30 */
31@GwtCompatible
32abstract class BstPath<N extends BstNode<?, N>, P extends BstPath<N, P>> {
33  private final N tip;
34  @Nullable
35  private final P prefix;
36
37  BstPath(N tip, @Nullable P prefix) {
38    this.tip = checkNotNull(tip);
39    this.prefix = prefix;
40  }
41
42  /**
43   * Return the end of this {@code BstPath}, the deepest node in the path.
44   */
45  public final N getTip() {
46    return tip;
47  }
48
49  /**
50   * Returns {@code true} if this path has a prefix.
51   */
52  public final boolean hasPrefix() {
53    return prefix != null;
54  }
55
56  /**
57   * Returns the prefix of this path, which reaches to the parent of the end of this path. Returns
58   * {@code null} if this path has no prefix.
59   */
60  @Nullable
61  public final P prefixOrNull() {
62    return prefix;
63  }
64
65  /**
66   * Returns the prefix of this path, which reaches to the parent of the end of this path.
67   *
68   * @throws IllegalStateException if this path has no prefix.
69   */
70  public final P getPrefix() {
71    checkState(hasPrefix());
72    return prefix;
73  }
74}
75