hadoop中InterfaceAudience 注解

InterfaceAudience 类包含三个注解类型，用来被说明被他们注解的类型的潜在的使用范围（audience）。
         @InterfaceAudience.Public： 对所有工程和应用可用
         @InterfaceAudience.LimitedPrivate： 仅限于某些特定工程，如Comomn，HDFS等
         @InterfaceAudience.Private： 仅限于Hadoop

 

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package org.apache.hadoop.classification;

import java.lang.annotation.Documented;

/**
 * Annotation to inform users of a package, class or method's intended audience.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class InterfaceAudience {
  /**
   * Intended for use by any project or application.
   */
  @Documented public @interface Public {};
  
  /**
   * Intended only for the project(s) specified in the annotation.
   * For example, "Common", "HDFS", "MapReduce", "ZooKeeper", "HBase".
   */
  @Documented public @interface LimitedPrivate {
    String[] value();
  };
  
  /**
   * Intended for use only within Hadoop itself.
   */
  @Documented public @interface Private {};

  private InterfaceAudience() {} // Audience can't exist on its own
}