1 /*
2  * Copyright (C) 2010 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package android.util;
18 
19 import android.compat.annotation.UnsupportedAppUsage;
20 
21 /**
22  * Singleton helper class for lazily initialization.
23  *
24  * Modeled after frameworks/base/include/utils/Singleton.h
25  *
26  * @hide
27  */
28 public abstract class Singleton<T> {
29 
30     @UnsupportedAppUsage
Singleton()31     public Singleton() {
32     }
33 
34     @UnsupportedAppUsage
35     private T mInstance;
36 
create()37     protected abstract T create();
38 
39     @UnsupportedAppUsage
get()40     public final T get() {
41         synchronized (this) {
42             if (mInstance == null) {
43                 mInstance = create();
44             }
45             return mInstance;
46         }
47     }
48 }
49