android/annotation/Nullable.java

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package android.annotation;

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.RetentionPolicy.SOURCE;

import android.annotation.SystemApi.Client;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Denotes that a parameter, field or method return value can be null.
 * <p>
 * When decorating a method call parameter, this denotes that the parameter can
 * legitimately be null and the method will gracefully deal with it. Typically
 * used on optional parameters.
 * <p>
 * When decorating a method, this denotes the method might legitimately return
 * null.
 * <p>
 * This is a marker annotation and it has no specific attributes.
 *
 * @paramDoc This value may be {@code null}.
 * @returnDoc This value may be {@code null}.
 * @hide
 */
@Retention(SOURCE)
@Target({METHOD, PARAMETER, FIELD})
@SystemApi(client = Client.MODULE_LIBRARIES)
public @interface Nullable {
}