annotation/annotation/src/main/java/androidx/annotation/GuardedBy.java

/*
 * Copyright (C) 2017 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 androidx.annotation;

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

/**
 * Denotes that the annotated method or field can only be accessed when holding the referenced lock.
 * <p>
 * Example:
 * <pre>
 * final Object objectLock = new Object();
 *
 * {@literal @}GuardedBy("objectLock")
 * volatile Object object;
 *
 * Object getObject() {
 *     synchronized (objectLock) {
 *         if (object == null) {
 *             object = new Object();
 *         }
 *     }
 *     return object;
 * }</pre>
 */
@Target({ElementType.FIELD, ElementType.METHOD})
@Retention(RetentionPolicy.CLASS)
public @interface GuardedBy {
    String value();
}