start again after no data entry

[aconti]

Hello,

I want to start the program from the beginning if upd.equals is left empty as now I am having an error.

import javax.swing.JOptionPane;
//import java.util.Scanner;



public class marks {

	public static void main(String[] args) {
		
		//Scanner scan = new Scanner(System.in);
		
		int marks = 0;
		
		
		
		
		for (int x=1; x<11; x++){
			String upd = JOptionPane.showInputDialog("Please enter mark number " + x);
			
			if (upd.equals("")){
				JOptionPane.showMessageDialog(null, "Please Enter a Mark ! ");
				x--;
				
			}else{
				System.out.println("Proceed");
			}
			
			int upd1 = Integer.parseInt(upd);
			
	
			
			marks = marks + upd1;
			
		
			//System.out.println(upd1);
			
			
			
			
		}
		
	
		
		
		
		JOptionPane.showMessageDialog(null, "The Total mark is " + marks);
	

	}

}

Thanks !

[Junky]

I am having an error.

We don't read minds. Post the full and exact error message.

[aconti]

Exception in thread "main" java.lang.NumberFormatException: For input string: ""
	at java.lang.NumberFormatException.forInputString(Unknown Source)
	at java.lang.Integer.parseInt(Unknown Source)
	at java.lang.Integer.parseInt(Unknown Source)
	at marks.main(marks.java:28)

[Junky]

Obviously "" (an empty string) is not a valid int and cannot be parsed. You do a check to see if upd is equal to "" so perhaps you should only parse upd if it is not "". Along the same lines what will your code do if user enters "Fred"?

[mine0926]

"" and null are not the same. You are not checking upd if it is null. In this case, upd is null but
since your just checking if upd is equals to "" then it continue to parse upd to integer eventhough it is null

[aconti]

thanks but how do I parse only if upd is not equals to ""

[aconti]

ok found out, just copied the parse section in the else section inside the if condition as it was out !

[aconti]

to make the program better as you told me:

Along the same lines what will your code do if user enters "Fred"?

how can I check the string only to accept values from 1 - 100 ?

[Junky]

In this case, upd is null

Not it isn't. The error message clearly says that the invalid input is an empty String. Besides JOptionPane will never return null.

[DarrylBurke]

Not it isn't. The error message clearly says that the invalid input is an empty String. Besides JOptionPane will never return null.

Yes it can.

System.out.println(JOptionPane.showInputDialog(null,
        "Close this dialog using the [x] button in the title bar") == null);

db

[Junky]

I cry foul. Well I was talking about getting user input. Interesting it also returns null if the Cancel button is clicked.

[DarrylBurke]

As documented, but unfortunately only for one of the many overloads.

db