DroidUuidFactory.java

public class DroidUuidFactory {

    protected static final String PREFS_FILE = "device_uuid.xml";
    protected static final String PREFS_DEVICE_UUID = "device_uuid";

    protected volatile static UUID uuid;

    public DroidUuidFactory(Context context){
        if( uuid ==null ) {
            synchronized (DroidUuidFactory.class) {
                if( uuid == null) {
                    final SharedPreferences prefs = context.getSharedPreferences( PREFS_FILE, 0);
                    final String id = prefs.getString(PREFS_DEVICE_UUID, null );
                    if (id != null) {
                        // Use the ids previously computed and stored in the prefs file
                        uuid = UUID.fromString(id);

                    } else {
                        final UUID randomUUID;

                        randomUUID = UUID.randomUUID();

                        uuid = randomUUID;



                        prefs.edit().putString(PREFS_DEVICE_UUID, uuid.toString() ).apply();


                    }
                }
            }
        }


    }

}