NullPointerException error for an SQL code

Question

I've got this form which contains three text fields and two radio buttons. The form is supposed to calculate the bill amounts for a customer. I've written the following code and it shows a NullPointerException error.

int noproduct;
double totalprice, price, shipcharge;
try{
    Connection connection=getConnection();
    stmt=connection.createStatement();
    ResultSet rs1=stmt.executeQuery("Select count(ProductName) from buy;");
    ResultSet rs2=stmt.executeQuery("Select sum(price) as TPrice from buy;");
    noproduct=rs1.getInt("count(ProductName)");
    NoProducts.setText(""+noproduct);
    price=rs2.getDouble("TPrice");
    shipcharge=3 * noproduct;
    ShipCharges.setText(""+shipcharge);
    totalprice=price+shipcharge;
    TotalPrice.setText(""+totalprice);
    if(CashRB.isSelected()){
        totalprice=totalprice+(5*noproduct);
        JOptionPane.showMessageDialog(null,"You have paid the bill by Cash!");
    }
    else if(CCardRB.isSelected()){
        totalprice=totalprice-(5*noproduct);
        JOptionPane.showMessageDialog(null,"You have paid the bill using Credit Card!");
    }
}
catch(Exception ex){
    System.out.println(ex.toString());
    ex.printStackTrace();
}
finally{}

This line in specific shows the error:

noproduct=rs1.getInt("count(ProductName)");

I need an alternate code to display the same result as this.

As well as it shows these errors, which I don't really understand what they are:

java.lang.NullPointerException
        at com.mysql.jdbc.ResultSetImpl.buildIndexMapping(ResultSetImpl.java:709)
        at com.mysql.jdbc.ResultSetImpl.findColumn(ResultSetImpl.java:1069)
        at com.mysql.jdbc.ResultSetImpl.getInt(ResultSetImpl.java:2734)

Can anyone help me please? Thank you in advance.

Error at line 2734.. Did you consider refactoring code and breaking it into smaller parts? — svz, Nov 24 '13 at 18:54
@LuluLala: the other statement assigns an alias to the sum. Why don't you do the same thing in the first statement and assign an alias to the count? — JB Nizet, Nov 24 '13 at 18:56

score 1 · Accepted Answer · edited May 23 '17 at 12:04

1

change this to

 rs1.next();
 noproduct=rs1.getInt(1);

and see here

there is one ResultSet is allowed for one Statement. may be you got Exception in this case. because you used ResultSet res1 and rs2.

edited May 23 '17 at 12:04

Community

1
1

answered Nov 24 '13 at 18:54

subash

3,116
3
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It showed this error: `java.sql.SQLException: Operation not allowed after ResultSet closed` – LuluLala Nov 24 '13 at 19:08
I'm sorry, I'm new to this. Do you mean the code for the connection I made for the form with MySQL? – LuluLala Nov 24 '13 at 19:14
there is one `ResultSet` is allowed for one `Statement`. may be you got Exception in this case. because you used ResultSet rs1 and rs2. – subash Nov 24 '13 at 19:22
But it doesn't work if I use only one `ResultSet`. Is there any alternative for that? – LuluLala Nov 24 '13 at 19:27
if you use only one result set what exception you got..? – subash Nov 24 '13 at 19:28
It worked! I replaced `rs1` with `rs` which I used for both the queries. Thanks! – LuluLala Nov 24 '13 at 19:46

Rakesh KR · Answer 2 · 2013-11-24T19:09:59.867

0

Try this

ResultSet rs1=stmt.executeQuery("Select count(ProductName) as NoOfProducts from buy;");
rs1.next();
noproduct=rs1.getInt("NoOfProducts");

edited Nov 24 '13 at 19:09

answered Nov 24 '13 at 18:58

Rakesh KR

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score 0 · Answer 3 · answered Nov 24 '13 at 19:00

0

You need rs1.next() cursor to invoke value.

 while(rs1.next()){
   noproduct=rs1.getInt("count(ProductName)");
 }

answered Nov 24 '13 at 19:00

Masudul

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It shows a warning that `noproducts` might not be initialized for the next line. – LuluLala Nov 24 '13 at 19:10
The warning is because you declared `noproduct` without default value. Assign a default value in case the code does not execute the while block (`noproduct = 0;` before the while) – clubifaximatic Nov 24 '13 at 19:39

score 0 · Answer 4 · answered Jan 31 '16 at 06:23

This kind of error occurs when you directly access resultset without itrating the it.

You can solve problem by itrate the resultset and get value:

while (resultSet.next()) 
        {
            JSONObject response = new JSONObject();
            response.put("dish_title", resultSet.getString("dish_title"));
            int remainingQuantity =  resultSet.getInt("quantity") -  
        }

NullPointerException error for an SQL code

4 Answers4