001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    package org.apache.hadoop.classification;
019    
020    import java.lang.annotation.Documented;
021    import java.lang.annotation.Retention;
022    import java.lang.annotation.RetentionPolicy;
023    
024    /**
025     * Annotation to inform users of a package, class or method's intended audience.
026     */
027    @InterfaceAudience.Public
028    @InterfaceStability.Evolving
029    public class InterfaceAudience {
030      /**
031       * Intended for use by any project or application.
032       */
033      @Documented
034      @Retention(RetentionPolicy.RUNTIME)
035      public @interface Public {};
036      
037      /**
038       * Intended only for the project(s) specified in the annotation.
039       * For example, "Common", "HDFS", "MapReduce", "ZooKeeper", "HBase".
040       */
041      @Documented
042      @Retention(RetentionPolicy.RUNTIME)
043      public @interface LimitedPrivate {
044        String[] value();
045      };
046      
047      /**
048       * Intended for use only within Hadoop itself.
049       */
050      @Documented
051      @Retention(RetentionPolicy.RUNTIME)
052      public @interface Private {};
053    
054      private InterfaceAudience() {} // Audience can't exist on its own
055    }