1 /*
2  * Copyright (C) 2017 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 androidx.annotation;
18 
19 import java.lang.annotation.ElementType;
20 import java.lang.annotation.Retention;
21 import java.lang.annotation.RetentionPolicy;
22 import java.lang.annotation.Target;
23 
24 /**
25  * Denotes that the annotated method or field can only be accessed when holding the referenced lock.
26  * <p>
27  * Example:
28  * <pre>
29  * final Object objectLock = new Object();
30  *
31  * {@literal @}GuardedBy("objectLock")
32  * volatile Object object;
33  *
34  * Object getObject() {
35  *     synchronized (objectLock) {
36  *         if (object == null) {
37  *             object = new Object();
38  *         }
39  *     }
40  *     return object;
41  * }</pre>
42  */
43 @Target({ ElementType.FIELD, ElementType.METHOD })
44 @Retention(RetentionPolicy.CLASS)
45 public @interface GuardedBy {
value()46     String value();
47 }
48