Getting nullpointerexception: exception in thread "AWT-eventqueue-0" java.lang.nullpointerexception

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I am trying to solve this issue since 2 days but I am not able to solve it. Basically I am want that if the result of

Java

pst = conn.prepareStatement("select * from employee where cnic = ?");

is returning empty set than

if(rs.next())

will execute and if it returning some data than program skip if and execute else part. I don't know where I am getting NullPointerException. I think I am getting exception after the execution of

pst = conn.prepareStatement("select * from employee where cnic = ?");

I don't how to solve it so please help me

Java

try {
                    while(!bool){
                        pst = conn.prepareStatement("select * from employee where cnic = ?");
                        System.out.print(s9);
                        pst.setString(1, s9);
                        rs = pst.executeQuery();
                        if(rs.next()){
                            pst = conn.prepareStatement("insert into employee(id,firstname,lastname,age,gender,job,salary,phone,cnic,email) values(?,?,?,?,?,?,?,?,?,?)");
                            pst.setString(1, s1);
                            pst.setString(2, s2);
                            pst.setString(3, s3);
                            pst.setString(4, s4);
                            pst.setString(5, s5);
                            pst.setString(6, s6);
                            pst.setString(7, s7);
                            pst.setString(8, s8);
                            pst.setString(9, s9);
                            pst.setString(10, s10);
                            JOptionPane.showMessageDialog(null, "Employee Added Successfully");
                            new EmployeeMenu().setVisible(true);
                            setVisible(false);
                            bool = true;
                        }else {
                            JOptionPane.showMessageDialog(null, "This CNIC Number is Already Registered");
                            s9 = JOptionPane.showInputDialog("Enter a correct CNIC Number:");                           
                        }
                    }
                } catch (SQLException ex) {
                    Logger.getLogger(AddEmployee.class.getName()).log(Level.SEVERE, null, ex);
                }

What I have tried:

I tried many things and not able to solve the problem so please help me to solve this.

Posted 26-May-21 23:20pm

Safin Mahesania

Updated 27-May-21 0:02am

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Richard MacCutchan · Answer 1 · 2021-05-27T00:00:00

Solution 1

Most likely the executeQuery does not return any records and thus rs is null.

Java

rs = pst.executeQuery();
if(rs.next()){

So calling next on a null object raises the exception you see.

Use your debugger to verify and see exactly what is happening.

Posted 27-May-21 0:00am

Richard MacCutchan

Comments

Safin Mahesania 27-May-21 6:31am

@Richard MacCutchan But I want that if the result is empty than if runs and if result is not empty so what condition I should apply

Richard MacCutchan 27-May-21 7:01am

Like I said, you first need to use the debugger to check that this is the actual problem. If you confirm that the return value is null then you can test for that condition and take some action.

OriginalGriff · Answer 2 · 2021-05-27T00:02:00

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterday's shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, VS will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!