import io.realm.RealmObject;
import io.realm.annotations.Index;
import io.realm.annotations.PrimaryKey;

public class Person extends RealmObject {
    @PrimaryKey
    private long id;

    @Index
    private String name;

    private int age;

    public long getId() { return id; }

    public void setId(long id) { this.id = id; }

    public String getName() { return name; }

    public void setName(String name) { this.name = name; }

    public int getAge() { return age; }

    public void setAge(int age) {this.age = age; }

}

06-01 08:35:54.755 21140-21140/realm.test.app.testrealm E/AndroidRuntime: FATAL EXCEPTION: main
   Process: realm.test.app.testrealm, PID: 21140
   java.lang.RuntimeException: Unable to start activity ComponentInfo{realm.test.app.testrealm/realm.test.app.testrealm.MainActivity}: io.realm.exceptions.RealmMigrationNeededException: RealmMigration must be provided
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2339)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2413)
       at android.app.ActivityThread.access$800(ActivityThread.java:155)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1317)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:135)
       at android.app.ActivityThread.main(ActivityThread.java:5343)
       at java.lang.reflect.Method.invoke(Native Method)
       at java.lang.reflect.Method.invoke(Method.java:372)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)
    Caused by: io.realm.exceptions.RealmMigrationNeededException: RealmMigration must be provided
       at io.realm.BaseRealm.migrateRealm(BaseRealm.java:680)
       at io.realm.Realm.migrateRealm(Realm.java:1221)
       at io.realm.Realm.migrateRealm(Realm.java:1208)
       at io.realm.Realm.createInstance(Realm.java:235)
       at io.realm.RealmCache.createRealmOrGetFromCache(RealmCache.java:126)
       at io.realm.Realm.getDefaultInstance(Realm.java:174)
       at realm.test.app.testrealm.MainActivity.onCreate(MainActivity.java:27)
       at android.app.Activity.performCreate(Activity.java:6010)
       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1129)
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2292)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2413)
       at android.app.ActivityThread.access$800(ActivityThread.java:155)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1317)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:135)
       at android.app.ActivityThread.main(ActivityThread.java:5343)
       at java.lang.reflect.Method.invoke(Native Method)
       at java.lang.reflect.Method.invoke(Method.java:372)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)

public class MyApplication extends Application {

    private static final String TAG = "MyApplication";

    public void onCreate() {
        super.onCreate();
        Stetho.initialize(
                Stetho.newInitializerBuilder(this)
                        .enableDumpapp(Stetho.defaultDumperPluginsProvider(this))
                        .enableWebKitInspector(RealmInspectorModulesProvider.builder(this).build())
                        .build());

        Log.d(TAG, "onCreate: Realm Object");

        RealmConfiguration realmConfiguration = new RealmConfiguration.Builder(this)
                .build();
        Realm.setDefaultConfiguration(realmConfiguration);

    }


}

public class MyApplication extends Application {

    private static final String TAG = "MyApplication";

    public void onCreate() {
        super.onCreate();
        Stetho.initialize(
                Stetho.newInitializerBuilder(this)
                        .enableDumpapp(Stetho.defaultDumperPluginsProvider(this))
                        .enableWebKitInspector(RealmInspectorModulesProvider.builder(this).build())
                        .build());

        Log.d(TAG, "onCreate: Realm Object");

        RealmConfiguration realmConfiguration = new RealmConfiguration.Builder(this)
                .schemaVersion(1)
                .deleteRealmIfMigrationNeeded()
                .migration(new MyMigration())
                .build();
        Realm.setDefaultConfiguration(realmConfiguration);

    }

    private class MyMigration implements RealmMigration {
        @Override
        public void migrate(DynamicRealm realm, long oldVersion, long newVersion) {
            Log.i(TAG, "migrate() called with: " + "realm = [" + realm + "], oldVersion = [" + oldVersion + "], newVersion = [" + newVersion + "]");
        }
    }
}