code: /*
   * Copyright (C) 2008 Google Inc.
   *
   * 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 tools.com.google.gson.annotations;
  
  import java.lang.annotation.Documented;
  import java.lang.annotation.ElementType;
  import java.lang.annotation.Retention;
  import java.lang.annotation.RetentionPolicy;
  import java.lang.annotation.Target;
  
  /**
   * An annotation that indicates the version number since a member or a type has been present.
   * This annotation is useful to manage versioning of your Json classes for a web-service.
   *
   * <p>
   * This annotation has no effect unless you build {@link com.google.gson.Gson} with a
   * {@link com.google.gson.GsonBuilder} and invoke
   * {@link com.google.gson.GsonBuilder#setVersion(double)} method.
   *
   * <p>Here is an example of how this annotation is meant to be used:</p>
   * <pre>
   * public class User {
   *   private String firstName;
   *   private String lastName;
   *   &#64Since(1.0) private String emailAddress;
   *   &#64Since(1.0) private String password;
   *   &#64Since(1.1) private Address address;
   * }
   * </pre>
   *
   * <p>If you created Gson with {@code new Gson()}, the {@code toJson()} and {@code fromJson()}
   * methods will use all the fields for serialization and deserialization. However, if you created
   * Gson with {@code Gson gson = new GsonBuilder().setVersion(1.0).create()} then the
   * {@code toJson()} and {@code fromJson()} methods of Gson will exclude the {@code address} field
   * since it's version number is set to {@code 1.1}.</p>
   *
   * @author Inderjeet Singh
   * @author Joel Leitch
   */
  @Documented
  @Retention(RetentionPolicy.RUNTIME)
  @Target({ElementType.FIELD, ElementType.TYPE})
  public @interface Since {
    /**
     * the value indicating a version number since this member
     * or type has been present.
     */
    double value();
  }
  