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
– svz, Commented Nov 24, 2013 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
– JB Nizet, Commented Nov 24, 2013 at 18:56

Community · Accepted Answer · 2017-05-23 12:04:08Z

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, 2017 at 12:04

CommunityBot

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answered Nov 24, 2013 at 18:54

subash

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6 Comments

LuluLala Over a year ago

It showed this error: java.sql.SQLException: Operation not allowed after ResultSet closed

LuluLala Over a year ago

I'm sorry, I'm new to this. Do you mean the code for the connection I made for the form with MySQL?

subash Over a year ago

there is one ResultSet is allowed for one Statement. may be you got Exception in this case. because you used ResultSet rs1 and rs2.

LuluLala Over a year ago

But it doesn't work if I use only one ResultSet. Is there any alternative for that?

subash Over a year ago

if you use only one result set what exception you got..?

|

Masudul · Accepted Answer · 2013-11-24 19:00:11Z

0

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

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

answered Nov 24, 2013 at 19:00

Masudul

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2 Comments

LuluLala Over a year ago

It shows a warning that noproducts might not be initialized for the next line.

clubifaximatic Over a year ago

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)

Rakesh KR · Accepted Answer · 2013-11-24 19:09:59Z

0

Try this

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

edited Nov 24, 2013 at 19:09

answered Nov 24, 2013 at 18:58

Rakesh KR

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Comments

Gaurav vijayvargiya · Accepted Answer · 2016-01-31 06:23:37Z

0

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") -  
        }

answered Jan 31, 2016 at 6:23

Gaurav vijayvargiya

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