title: "Class must either be declared abstract or implement abstract method" error when creating class
body: <p>I created a new <code>class</code> on Android Studio:</p>
  
  <pre><code>package com.apress.gerber.contentprovider;
  
  import android.content.ContentProvider;
  
  import java.util.HashMap;
  
  /**
   * Created by BBC on 2017/9/21.
   */
  public class BookProvider extends  ContentProvider{
  
  }
  </code></pre>
  
  <p>For <code>public class BookProvider extends  ContentProvider</code> there is an error message:</p>
  
  <blockquote>
    <p>Class 'BookProvider' must either be declared abstract or implement
    abstract method 'getType(Uri) in 'ContentProvider'</p>
  </blockquote>
  
  <p>How to fix it?</p>