Reboot programmatically Android Things

I want to use this code in order to reboot my RPI3 running Android Things:

public static void Reboot()
{
    try {
        Process proc = Runtime.getRuntime().exec(new String[]{"su", "-c", "reboot"});
        proc.waitFor();
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

I get the following error:

java.io.IOException: Cannot run program "su": error=13, Permission denied

I add to the manifest all the permission

<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.DOWNLOAD_WITHOUT_NOTIFICATION" />
<uses-permission android:name="android.permission.KILL_BACKGROUND_PROCESSES" />
<uses-permission android:name="android.permission.ACCESS_SUPERUSER" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.SET_TIME_ZONE"/>
<uses-permission android:name="android.permission.SHUTDOWN"/>

Am I missing something?