1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27
28 package org.apache.http.protocol;
29
30 import java.util.Collection;
31 import java.util.HashMap;
32 import java.util.LinkedList;
33 import java.util.Map;
34
35 /**
36 * Builder class to build a linked list (chain) of unique class instances. Each class can have
37 * only one instance in the list. Useful for building lists of protocol interceptors.
38 *
39 * @see ImmutableHttpProcessor
40 *
41 * @since 4.3
42 */
43 final class ChainBuilder<E> {
44
45 private final LinkedList<E> list;
46 private final Map<Class<?>, E> uniqueClasses;
47
48 public ChainBuilder() {
49 this.list = new LinkedList<E>();
50 this.uniqueClasses = new HashMap<Class<?>, E>();
51 }
52
53 private void ensureUnique(final E e) {
54 final E previous = this.uniqueClasses.remove(e.getClass());
55 if (previous != null) {
56 this.list.remove(previous);
57 }
58 this.uniqueClasses.put(e.getClass(), e);
59 }
60
61 public ChainBuilder<E> addFirst(final E e) {
62 if (e == null) {
63 return this;
64 }
65 ensureUnique(e);
66 this.list.addFirst(e);
67 return this;
68 }
69
70 public ChainBuilder<E> addLast(final E e) {
71 if (e == null) {
72 return this;
73 }
74 ensureUnique(e);
75 this.list.addLast(e);
76 return this;
77 }
78
79 public ChainBuilder<E> addAllFirst(final Collection<E> c) {
80 if (c == null) {
81 return this;
82 }
83 for (final E e: c) {
84 addFirst(e);
85 }
86 return this;
87 }
88
89 public ChainBuilder<E> addAllFirst(final E... c) {
90 if (c == null) {
91 return this;
92 }
93 for (final E e: c) {
94 addFirst(e);
95 }
96 return this;
97 }
98
99 public ChainBuilder<E> addAllLast(final Collection<E> c) {
100 if (c == null) {
101 return this;
102 }
103 for (final E e: c) {
104 addLast(e);
105 }
106 return this;
107 }
108
109 public ChainBuilder<E> addAllLast(final E... c) {
110 if (c == null) {
111 return this;
112 }
113 for (final E e: c) {
114 addLast(e);
115 }
116 return this;
117 }
118
119 public LinkedList<E> build() {
120 return new LinkedList<E>(this.list);
121 }
122
123 }