In this example,we will have a layout in which there are two fragments in an activity.

In our mobile phone,we will show only one fragment but in tablets,we will show both fragments simuntanously.

activity_main.xml (for mobile phone)

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical">
   <fragment
       android:id="@+id/main_panel"
       class="com.multipaneui.fragment.MainFragment"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
/>
</RelativeLayout>

Now make another layout folder with name layout-sw600dp and inside that folder,make a layout file with same name(activity_main.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:baselineAligned="false"
    android:weightSum="1">
    <fragment
        android:id="@+id/side_panel"
        android:layout_weight="0.3"
        class="com.multipaneui.fragment.SideFragment"
        android:layout_width="wrap_content"
        android:layout_height="match_parent" />
    <fragment
        android:id="@+id/main_panel"
        class="com.multipaneui.fragment.MainFragment"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_weight="0.7" />
</LinearLayout>

Simple layout folder is for mobile but layout-sw600dp is for tablets of screen resolution>=600dp.

Now for java file,MainActivity.java

public class MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getSimpleName();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

That's it folks.Now u can test your app at mobile and tablet.Have fun:)