How can I add error handling facilities to this code?

Question

Hi everyone, i have this code that needs some error handling facilities (messages that warn user the data inputted is not valid that prvent crashing) added to it. I have no idea on how to do it and i accept any ideas. I'll post the code in two sections as it doesnt fit. The code works by recieveing inputs for student grades and calculating the total and the average. That works fine, but i need to include an error handling facility that doesnt allow the user to input letters, special characters or numbers outside the range 1-10. Can anyone help?

Answer 1

Code Part 1:
import java.text.DecimalFormat;
import javax.swing.JOptionPane;
import javax.swing.*;
import java.util.*;
//Defines the counter for the student count and uses a usage method to
public class EdronProject {
  private              int           studentCount;
  private static final String        USAGE = "Usage: java EdronProject <student count>";
  private              List<Student> list;
//Set up the counter fo the number of students and the list in which
//each student's information is saved once processed
  public EdronProject(int count) {
    studentCount = count;
    list = new ArrayList<Student>();
//Checks the number or arguments, and it executes the rest of the code
//if there is 1 argument or more (the number of arguments = the number
//of students being processed)
  public static void main( String args[] )  throws NumberFormatException {
   int count = 0;
   switch (args.length) {
     case 1: count = Integer.parseInt(args[0]); break;
     default: System.out.println(USAGE); System.exit(0);
  //Defines method for processing and printing students within the
  //EdronProject class 
    EdronProject edp = new EdronProject(count);
    edp.processStudents();
    edp.printStudents();
  class Student {
  //Define integer values for the 5 subject's grades, the gradeCounter (used
  //in the processing stage) and the student name string
      private int 
                gradeCounter,
                grade1,
                grade2,
                grade3,
                grade4,
                grade5;
     private double total;
     private String studentName;
//Use setter getter methods for the student name to be retrieved
    public void setStudentName(String name) {
       studentName = name;
    public String getStudentName() {
      return( studentName );
//Use setter getter methods for the grades inputted to be retrieved
//by the processing stage
    public void setGrade(int gradeNo, int grade)  throws IllegalArgumentException {
      switch( gradeNo) {
        case 1 : grade1 = grade; break;
        case 2 : grade2 = grade; break;
        case 3 : grade3 = grade; break;
        case 4 : grade4 = grade; break;
        case 5 : grade5 = grade; break;
        default: throw new IllegalArgumentException("ERROR: Bad grade number passed!");
  //Increase grade counter for it to register the number of grades inputted
  //by user
      gradeCounter++;
    public int getGrade(int gradeNo)  throws IllegalArgumentException {
      int grade = 0;
      switch( gradeNo) {
        case 1 : grade = grade1; break;
        case 2 : grade = grade2; break;
        case 3 : grade = grade3; break;
        case 4 : grade = grade4; break;
        case 5 : grade = grade5; break;
        default: throw new IllegalArgumentException("ERROR: Bad grade number passed!");
//Return grade values for them to be used by the processing stage   
      return( grade );
    }