NullPointerException error [closed]

  

Caused by: java.lang.NullPointerException        at DAO.Database.ScheduleReview (Database.java:184)

This error was displayed in my logcat .

The method:

public boolean verificaSeTemRegistroNaTabela(String tabela){
    String sqlSelect = "SELECT * FROM '" + tabela + "'";
    Cursor res = db.rawQuery(sqlSelect, null);
    if (res.getCount() > 0){
        return true;
    }
    return false;
}

Line with error:

Cursor res = db.rawQuery(sqlSelect, null);