1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20 package org.apache.mina.util;
21
22 /**
23 * An abstract class which provides semantics for an object which will be only
24 * fully initialized when requested to. It allows to avoid loosing time when
25 * early initializing unnecessary objects.
26 *
27 * @param <V> The value type
28 *
29 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
30 * @since MINA 2.0.0-M2
31 */
32 public abstract class LazyInitializer<V> {
33
34 /**
35 * The value that results on the {@link #init()} call. If null,
36 * it means that the value has not been initialized yet.
37 */
38 private V value;
39
40 /**
41 * Initializes the value.
42 *
43 * @return the initialized value
44 */
45 public abstract V init();
46
47 /**
48 * @return the value resulting from the initialization.
49 */
50 public V get() {
51 if (value == null) {
52 value = init();
53 }
54
55 return value;
56 }
57 }