1 /*
2  * Copyright (C) 2013 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 package android.annotation;
17 
18 import static java.lang.annotation.ElementType.FIELD;
19 import static java.lang.annotation.ElementType.METHOD;
20 import static java.lang.annotation.ElementType.PARAMETER;
21 import static java.lang.annotation.RetentionPolicy.SOURCE;
22 
23 import android.annotation.SystemApi.Client;
24 
25 import java.lang.annotation.Retention;
26 import java.lang.annotation.Target;
27 
28 /**
29  * Denotes that a parameter, field or method return value can be null.
30  * <p>
31  * When decorating a method call parameter, this denotes that the parameter can
32  * legitimately be null and the method will gracefully deal with it. Typically
33  * used on optional parameters.
34  * <p>
35  * When decorating a method, this denotes the method might legitimately return
36  * null.
37  * <p>
38  * This is a marker annotation and it has no specific attributes.
39  *
40  * @paramDoc This value may be {@code null}.
41  * @returnDoc This value may be {@code null}.
42  * @hide
43  */
44 @Retention(SOURCE)
45 @Target({METHOD, PARAMETER, FIELD})
46 @SystemApi(client = Client.MODULE_LIBRARIES)
47 public @interface Nullable {
48 }
49