1 /*
2 * Copyright (c) 2001-2017, Zoltan Farkas All Rights Reserved.
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2.1 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Additionally licensed with:
19 *
20 * Licensed under the Apache License, Version 2.0 (the "License");
21 * you may not use this file except in compliance with the License.
22 * You may obtain a copy of the License at
23 *
24 * http://www.apache.org/licenses/LICENSE-2.0
25 *
26 * Unless required by applicable law or agreed to in writing, software
27 * distributed under the License is distributed on an "AS IS" BASIS,
28 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
29 * See the License for the specific language governing permissions and
30 * limitations under the License.
31 */
32 package org.spf4j.base;
33
34 import javax.annotation.Nullable;
35
36 /**
37 *
38 * @author Zoltan Farkas
39 */
40 public abstract class NullAbleOptional<T> {
41
42 public static final NullAbleOptional EMPTY = new NullAbleOptional() {
43 @Override
44 public Object get() {
45 throw new UnsupportedOperationException("Optional is empty");
46 }
47
48 @Override
49 public boolean isPresent() {
50 return false;
51 }
52 };
53
54 public static NullAbleOptional empty() {
55 return EMPTY;
56 }
57
58 @Nullable
59 public abstract T get();
60
61 public abstract boolean isPresent();
62
63 @Override
64 public final String toString() {
65 return "Optional{present = " + isPresent() + ", value=" + get() + '}';
66 }
67
68 public static <T> NullAbleOptional<T> of(@Nullable final T value) {
69 return new NullAbleOptional<T>() {
70 @Override
71 @Nullable
72 public T get() {
73 return value;
74 }
75
76 @Override
77 public boolean isPresent() {
78 return true;
79 }
80 };
81 }
82
83 }
84