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/*
 * Copyright 2017 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.firebase.database;

/**
 * Due to the way that Java implements generics (type-erasure), it is necessary to use a slightly
 * more complicated method to properly resolve types for generic collections at runtime. To solve
 * this problem, Firebase Database accepts subclasses of this class in calls to getValue ({@link
 * com.google.firebase.database.DataSnapshot#getValue(GenericTypeIndicator)}, {@link
 * MutableData#getValue(GenericTypeIndicator)}) and returns a properly-typed generic collection.
 *
 * As an example, you might do something like this to get a list of Message instances from a
 * {@link DataSnapshot}: 

 * 

 *
 * 

 *     class Message {
 *         private String author;
 *         private String text;
 *
 *         private Message() {}
 *
 *         public Message(String author, String text) {
 *             this.author = author;
 *             this.text = text;
 *         }
 *
 *         public String getAuthor() {
 *             return author;
 *         }
 *
 *         public String getText() {
 *             return text;
 *         }
 *     }
 *
 *     // Later ...
 *
 *     GenericTypeIndicator<List<Message>> t = new GenericTypeIndicator<List<
 *     Message>>()
 * {};
 *     List<Message> messages = snapshot.getValue(t);
 *
 * 
 *
 * @param  The type of generic collection that this instance servers as an indicator for
 */
public abstract class GenericTypeIndicator {
  // TODO: This is a legacy class that inherited from TypeIndicator from Jackson to be
  // able to resolve generic types. We need a new solution going forward.
}