title: Realm clear DB when the class changes
body: <p>Why is Realm completely cleared when changing the database class? That is, I had a class
  <strong>Weapon.class</strong></p>
  
  <pre><code>public class Weapon extends RealmObject {
  
      @PrimaryKey
      private int ID;
      private String NameWeapon;
  
      //Constructor, getters, setters...
  
  }
  </code></pre>
  
  <p>And everything is fine, the data is saved and read without problems, when adding new entries nothing flies. But, for example, I need to change the class</p>
  
  <pre><code>public class Weapon extends RealmObject {
  
      @PrimaryKey
      private int ID;
      private String NameWeapon;
      private float Cost = 0f;
  
      //Constructor, getters, setters...
  
  }
  </code></pre>
  
  <p>I added a new variable to the class, and if I start the application, it will crash, because there will not be anything in the database, Realm will not let the old records be read. And if you rebuild the database (insert the records by default), then the data that was entered by the user will be lost. </p>