help with GUI, Exception

[ngnt4]

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class TravelExpenses extends JPanel
 {
  private JTextField days;           //declaring textfields and labels
  private JTextField lodging;
  private JTextField airfare;
  private JTextField taxiCost;
  private JTextField miles;
  private JTextField rental;
  private JTextField seminarFees; 
  private JTextField parkingFees;
  private JLabel daysL;
  private JLabel lodgingL;
  private JLabel airfareL;
  private JLabel taxiCostL;
  private JLabel milesL;
  private JLabel rentalL;
  private JLabel seminarFeesL;
  private JLabel parkingFeesL; 
String input;
//int day;
double day, lodge,air,taxi,mile,rentals,sem,park;
 /**
 Constructorr
 */
  public TravelExpenses()
  	{
     setLayout(new GridLayout(8,1 ));
     days = new JTextField(4);
     lodging = new JTextField(4);
     airfare = new JTextField(4);
     taxiCost = new JTextField(4);
     miles = new JTextField(4);
     seminarFees = new JTextField(4);
     parkingFees = new JTextField(4);
  	  rental = new JTextField(4);  
	  setBorder(BorderFactory.createTitledBorder("Expenses"));


	  daysL= new JLabel("Duration of the Trip");
	  lodgingL = new JLabel("Lodging Cost");
	  airfareL = new JLabel("Airfare Cost");
	  taxiCostL = new JLabel("Taxi Expenses");
     milesL = new JLabel("Miles Driven");
     seminarFeesL= new JLabel("Seminar Fees");
     parkingFeesL= new JLabel("Parking Fees");
     rentalL = new JLabel("Rental Cost");
     add(daysL);
	  add(days);
	  add(lodgingL);
	  add(lodging);
	  add(airfareL);
	  add(airfare);
	  add(taxiCostL);
	  add(taxiCost);
	  add(milesL);
	  add(miles);
	  add(rentalL);
	  add(rental);
	  add(seminarFeesL);
	  add(seminarFees);
	  add(parkingFeesL);
	  add(parkingFees);
     
	  input = days.getText();
     day = Double.parseDouble(input);
     
	  input = lodging.getText();
	  lodge = Double.parseDouble(input); 
     
	  input = airfare.getText();
	  air = Double.parseDouble(input);
	  
	  input = taxiCost.getText();
	  taxi = Double.parseDouble(input);
	  
	  input = miles.getText();
	  mile = Double.parseDouble(input);
	  
	  input = rental.getText();
	  rentals = Double.parseDouble(input);
	  
	  input = seminarFees.getText();
	  sem = Double.parseDouble(input);
	  
	  input = parkingFees.getText();
	  park = Double.parseDouble(input);
 }//end of constructor
  public void setValues(int d,double l,double a,double t, double m,double r,double s,double p)
  {
  day = d;
  
  lodge = l;

  air = a;
  
  taxi = t;
  
  mile = m;
  
  rentals = r;
  
  sem = s;
  
  park = p;
  }   

public double getDays()
  {
   
   return day;
  }
public double getLodging()
  {
   return lodge;
  }
  
public double getAirfare()
 {
  return air;
 }
public double getTaxiCost()
 {
  return taxi;
 }
public double getMiles()
 {
  return mile;
 }
public double getRentalCost()
 {
  return rentals;
 }
 public double getSeminarFees()
  {
   return  sem;
  }
public double getParkingFees()
 {
  return park;
  }
 



}

Exception in thread "main" java.lang.NumberFormatException: empty String
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:994)
at java.lang.Double.parseDouble(Double.java:510)
at TravelExpenses.<init>(TravelExpenses.java:69)
at TravelGUI.<init>(TravelGUI.java:24)
at tets.main(tets.java:5)
I am having problems with this code i can get the window and everything else to work. however, when i try to parse the input from the JTextField for the days i get the above error and i cant figure out whats causing it.
please help
thanks in advance

[AndreiDMS]

Hi ngnt4,

input = days.getText();
day = Double.parseDouble(input);

The value returned by getText() method is an empty string(and not a parsable string), this is why you get the exception.
You can fix this by initializing the text field before calling the getText() method

days.setText("0");

Anyway I think you should move the parsing of text fields values in another method, and call it only when you need the values....

[BestJewSinceJC]

You could also (more correctly) fix it by using error checking. try... catch. Exception handling. Look them up. The poster above me, his solution won't work if a user goes back and edits something into a text field that isn't a double. Then you'll get the error again. Error checking will always work.

[ngnt4]

sweet thanks a lot...i was trying to figure out for a long time but as you can see im kinda new to this....thanks again i will look into both things