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+/*
+ * 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 com.google.gson.annotations;
+
+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
+ */
+@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();
+}