Executing query with condition in java (response = Illegal operation on empty result set)

Question

I have a problem, I want to execute query based on the condition. The concept is if the result is null, then execute another query. But when I try it, the result is an error

Illegal operation on empty result set`

My code:

String strSQL = "SELECT * FROM user WHERE userid=? AND password=? LIMIT 1;";

PreparedStatement pst=null;
pst = con.prepareStatement(strSQL);
pst.setString(1, userid);
pst.setString(2, password);

rs = pst.executeQuery();

if(rs.getString(1) == null && rs.getString(2) == null) {
   String strSQL = "SELECT userid FROM user WHERE userid=?;";
}

if(rs.next())
{   
    yoyo yo = new yoyo(); 
    yo.SetUserid(rs.getString(1));
    yo.SetUsername(rs.getString(2));
    yo.SetPosisi(rs.getString(5));
    lstLogin = yo;
}

Answer 1

At this line you will get the result set

rs = pst.executeQuery();

Now we want know that the rs is not null and also not empty. So we will give condition like this

if (rs != null && !rs.isBeforeFirst() ) {    
    String strSQL = "SELECT userid FROM user WHERE userid=?;"; 
}

Check this link for reference Check result set is empty or not

In your code it is not checking whether the ResultSet is empty or not.

Answer 2

You have not executed the query when if(rs.getString(1) == null && rs.getString(2) == null) condition is true.
To solve this, change the if condition as following:

if(!rs.next()){
    strSQL = "SELECT userid FROM user WHERE userid=?;";
    pst = con.prepareStatement(strSQL);
    pst.setString(1, userid);
    rs = pst.executeQuery();
}

Note: You have re-declared strSQL variable in if statement.