DB_Controller.java sqlite

public class DB_Controller extends SQLiteOpenHelper {
    public DB_Controller(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, "TEST.db", factory, version);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {

        sqLiteDatabase.execSQL("CREATE TABLE STUDENTS(ID INTEGER PRIMARY KEY AUTOINCREMENT, FIRSTNAME TEXT UNIQUE, LASTNAME TEXT);");



    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {

        sqLiteDatabase.execSQL("DROP TABLE IF EXISTS STUDENTS;");
        onCreate(sqLiteDatabase);


    }


    public void insert_student(String firstname, String lastname){

        ContentValues contentValues=new ContentValues();
        contentValues.put("FIRSTNAME",firstname);
        contentValues.put("LASTNAME",lastname);
        this.getWritableDatabase().insertOrThrow("STUDENTS","",contentValues);

    }

    public void delete_student(String firstname){

        this.getWritableDatabase().delete("STUDENTS","FIRSTNAME='"+firstname+"'",null);


    }

    public void update_student(String old_firstname, String new_firstname){

        this.getWritableDatabase().execSQL("UPDATE STUDENTS SET FIRSTNAME='"+new_firstname+"'WHERE FIRSTNAME='"+old_firstname+"'");
    }

    public void list_all_student(TextView textView){

        Cursor cursor=this.getReadableDatabase().rawQuery("SELECT * FROM STUDENTS",null);


        textView.setText("");
        while (cursor.moveToNext()){



            textView.append(cursor.getString(1) +" "+cursor.getString(2)+"\n");
        }

    }
}