Error in my applet..

Question

ok so i'm working on this small applet for an assignment for one of my programming classes. i've got it nearly completely written, But when i try to view it via the html page that its embedded in, all I get is a big blue square (blue isnt even supposed to be my applet's background...) When i view it on my machine, it doesnt give me any runtime errors, so I have no clue whats going on. I asked my professor for help on it but he wasnt able to give much..
heres a copy of my code:
import java.awt.*;
import java.applet.*;
import javax.swing.*;
import java.awt.event.*;
public class gpacalc extends JApplet implements ActionListener
    Container contentPane = getContentPane();
    JTextField [] outfields;
    JLabel out1;
    JLabel out2;
    JLabel out3;
     JTextField course;
     JTextField hours;
     JTextField grdexpt;
     int count = 0;
     int tothours = 0;
     int grdpts = 0;
     int totcredits = 0;
     double gpavg = 0;
    public void init()
    // Create a panel object and set its layout manager to put
    // the components in a column
        JPanel mainpanel = new JPanel();
        mainpanel.setLayout(new GridLayout(15, 2, 5, 5));
        mainpanel.setBackground(Color.yellow);
   // Create a labels for the form
        JLabel title = new JLabel("GPA Calculator");
        JLabel spaceholder = new JLabel(" ");
        JLabel courselab = new JLabel("Enter Course Name");
        JLabel hrslab = new JLabel("Enter Course Hrs.");
        JLabel gradelab = new JLabel("Enter Expected Grade");
        JLabel total = new JLabel("Total Semester Hrs.");
        JLabel grade = new JLabel("Total Grade Credits");
        JLabel gpa = new JLabel("Est. Grade Point Avg.");
     // Creates all of the needed text fields       
        course = new JTextField(30);
        hours = new JTextField(30);
          grdexpt = new JTextField(30);
          out1 = new JLabel("0");
          out2 = new JLabel("0");
        out3 = new JLabel("n/a");
    // Creates the ADD button
        JButton add = new JButton("Add Course Info.");
        add.addActionListener(this);
     // Adds everything to the panel
        mainpanel.add(title);
        mainpanel.add(spaceholder);
        mainpanel.add(courselab);
        mainpanel.add(course);i
        mainpanel.add(hrslab);
        mainpanel.add(hours);
        mainpanel.add(gradelab);
        mainpanel.add(grdexpt);
        mainpanel.add(total);
        mainpanel.add(out1);
        mainpanel.add(grade);
        mainpanel.add(out2);
        mainpanel.add(gpa);
        mainpanel.add(out3);
        mainpanel.add(add);
        mainpanel.add(spaceholder);
          //creates the output text fields in the array
          for(int x=0; x<6; x++)
               outfields[x] = new JTextField(30);
               outfields[x].setEditable(false);
               mainpanel.add(outfields[x]);
    // Now add the panel to the content pane
        contentPane.add(mainpanel);
     }  // End of init()
   public void actionPerformed(ActionEvent ev)
          int credits = 0;
          final int MAX = 6;
          String result = "";
          String grade ="";
          String hrs = "";
          count += 1;//count to see the number of courses added
             if(count<=MAX)
                  //sets result = Coursename - grade
               result = course.getText() + " - " +grdexpt.getText();
               grade = grdexpt.getText();
               //If-else stmts to assign grade point value for given grade
               if(grade.equals("a") || grade.equals("A"))
                    grdpts = 4;
               else if(grade.equals("b") || grade.equals("B"))
                    grdpts = 3;
               else if(grade.equals("c") || grade.equals("C"))
                    grdpts = 2;
               else if(grade.equals("d") || grade.equals("D"))
                    grdpts = 1;
               else
                    grdpts = 0;
                 //Reads in the text for the #hours, and parses it to an int
                 // for calculation.
                 hrs = hours.getText();
               credits = Integer.parseInt(hrs);
               tothours += credits;
               totcredits += (credits*grdpts);
                 gpavg = totcredits/tothours;//calculates GPA
                 //sets hours, credits, gpa fields
                 out1.setText(""+tothours);
                 out2.setText(""+totcredits);
                 out3.setText(""+gpavg);
                 //puts the result string into appropriate field
               outfields[count].setText(result);
               //clears out the input fields.
               course.setText("");
               hours.setText("");
               grdexpt.setText("");
            }//end if
            else
                 course.setText("Max Number of courses");
                 hours.setText("entered, please refresh");
                 grdexpt.setText("your browser.");
} heres the html file code that calls the applet:
<!DOCTYPE html PUBLIC "-//w3c//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!--gpadispp.html
A document to test the gpacalc JApplet
-->
<html>
<head><title>HTML Document that calls a JApplet </title>
</head>
<body>
<p>
<object codetype="application/java"
  code= "gpacalc.class"
  width="300"
  height="400">
</object>
</p>
</body>
</html>the source file is named gpacalc.java (gpacalc.class after compiled..)
if anyone can help me figure out where i've gone wrong, i'd be greatly appreciative.
thanks,
ceola

Answer 1

thanks for the assistance!
i went through what harmmeijer said, and this is the error it gave me.
java.lang.NullPointerException
     at gpacalc.init(gpacalc.java:82)
     at sun.applet.AppletPanel.run(Unknown Source)
     at java.lang.Thread.run(Unknown Source)
basic: Exception: java.lang.NullPointerException
heres a snip of the code that threw the exception:
          for(int x=0; x<6; x++)
               outfields[x] = new JTextField(30); //Exception thrown here
               outfields[x].setEditable(false);
               mainpanel.add(outfields[x]);
          }i have an idea of what the problem is, i'm going to try and fix it now. thanks again :)
ceola