001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.camel.processor.resequencer;
018
019 import java.util.TreeSet;
020
021 /**
022 * A sorted set of elements with additional methods for obtaining immediate
023 * successors and immediate predecessors of a given element in the sequence.
024 * Successors and predecessors are calculated by using a
025 * {@link SequenceElementComparator}.
026 *
027 * @version
028 */
029 public class Sequence<E> extends TreeSet<E> {
030
031 private static final long serialVersionUID = 5647393631147741711L;
032
033 private SequenceElementComparator<E> comparator;
034
035 /**
036 * Creates a new {@link Sequence} instance.
037 *
038 * @param comparator a strategy for comparing elements of this sequence.
039 */
040 public Sequence(SequenceElementComparator<E> comparator) {
041 super(comparator);
042 this.comparator = comparator;
043 }
044
045 /**
046 * Returns the immediate predecessor of the given element in this sequence
047 * or <code>null</code> if no predecessor exists.
048 *
049 * @param e an element which is compared to elements of this sequence.
050 * @return an element of this sequence or <code>null</code>.
051 */
052 public E predecessor(E e) {
053 E elem = lower(e);
054 if (elem == null) {
055 return null;
056 }
057 if (comparator.predecessor(elem, e)) {
058 return elem;
059 }
060 return null;
061 }
062
063 /**
064 * Returns the immediate successor of the given element in this sequence
065 * or <code>null</code> if no successor exists.
066 *
067 * @param e an element which is compared to elements of this sequence.
068 * @return an element of this sequence or <code>null</code>.
069 */
070 public E successor(E e) {
071 E elem = higher(e);
072 if (elem == null) {
073 return null;
074 }
075 if (comparator.successor(elem, e)) {
076 return elem;
077 }
078 return null;
079 }
080
081 /**
082 * Returns this sequence's comparator.
083 *
084 * @return this sequence's comparator.
085 */
086 public SequenceElementComparator<E> comparator() {
087 return comparator;
088 }
089
090 /**
091 * Returns the next higher element in the sequence to the given element. If
092 * the given element doesn't exist or if it is the last element in the
093 * sequence <code>null</code> is returned. <strong>Please note that this
094 * method is provided for compatibility with Java 5 SE. On a Java 6 SE
095 * platform the same method implemented by the {@link TreeSet}
096 * class should be used for better performance.</strong>
097 *
098 * @param e an element which is compared to elements of this sequence.
099 * @return an element of this sequence or <code>null</code>.
100 */
101 public E higher(E e) {
102 boolean found = false;
103 for (E current : this) {
104 if (found) {
105 return current;
106 }
107 if (comparator.compare(e, current) == 0) {
108 found = true;
109 }
110 }
111 return null;
112 }
113
114 /**
115 * Returns the next lower element in the sequence to the given element. If
116 * the given element doesn't exist or if it is the first element in the
117 * sequence <code>null</code> is returned. <strong>Please note that this
118 * method is provided for compatibility with Java 5 SE. On a Java 6 SE
119 * platform the same method implemented by the {@link TreeSet}
120 * class should be used for better performance.</strong>
121 *
122 * @param e an element which is compared to elements of this sequence.
123 * @return an element of this sequence or <code>null</code>.
124 */
125 public E lower(E e) {
126 E last = null;
127 for (E current : this) {
128 if (comparator.compare(e, current) == 0) {
129 return last;
130 }
131 last = current;
132 }
133 return last;
134 }
135
136 }