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 * @author The Apache MINA Project (dev@mina.apache.org)
28 * @since MINA 2.0.0-M2
29 */
30 public abstract class LazyInitializer<V> {
31
32 /**
33 * The value that results on the {@link #init()} call. If null,
34 * it means that the value has not been initialized yet.
35 */
36 private V value;
37
38 /**
39 * Initializes the value.
40 *
41 * @return the initialized value
42 */
43 public abstract V init();
44
45 /**
46 * Returns the value resulting from the initialization.
47 * @return the initialized value
48 */
49 public V get() {
50 if (value == null) {
51 value = init();
52 }
53
54 return value;
55 }
56 }