How can I add error handling facilities to this code?

[Diego Espinosa]

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 belllow. The code works by recieveing inputs through the console 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?

Program Name: The Edron Academy Grade Applet
NetBeans IDE 6.0
645 Words

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 );
    }
//Calculate the total by adding al 5 grade values  
    public double getTotal() {  
      total = (getGrade(1) + getGrade(2) + getGrade(3) + getGrade(4) +                 getGrade(5));  
//Total value returned for it to be used to calculate the average    
      return total;
    }
//Average is calculated by dividing the total over the grade 
//counter (number of grades inputted)
    public double getAverage() {  
      return ( (gradeCounter == 0) ? 0 : total / gradeCounter);
    }
  }
//Get input from user for student's 5 grades which are set as Grade 1, 2, 3, 4, 5 //and each five inputs for the student are saved to their own list along with the
//student name. Only integer values from 0 to 10 can be used.
  public void processStudents() {
    for (int counter = 0; counter < studentCount; counter++) {
      Student student = new Student();
      student.setStudentName(JOptionPane.showInputDialog("Enter student's  name:"));
      student.setGrade(1, Integer.parseInt(JOptionPane.showInputDialog( "Enter Student Grade for Psychology ")));
      student.setGrade(2, Integer.parseInt(JOptionPane.showInputDialog( "Enter Student Grade for Math ")));
      student.setGrade(3, Integer.parseInt(JOptionPane.showInputDialog( "Enter Student Grade for Art ")));
      student.setGrade(4, Integer.parseInt(JOptionPane.showInputDialog( "Enter Student Grade for Science ")));
      student.setGrade(5, Integer.parseInt(JOptionPane.showInputDialog( "Enter Student Grade for English ")));
      list.add(student);
    }
     
 
  }
//Begin the printting stage for each student entered
  public void printStudents() {
    for ( int i = 0; i < list.size(); i++ ) {
      Student s = list.get(i);
      printStudent(s);
    }
  }
//Print the student name along with each grade entered separated by commas
//and the total and average values in separate lines
  private void printStudent(Student student) {
    System.out.println("Student Name: "+student.getStudentName()
                      +", Pych: "+student.getGrade(1)
                      +", Math: "+student.getGrade(2)
                      +", Art : "+student.getGrade(3)
                      +", Sci : "+student.getGrade(4)
                      +", Eng : "+student.getGrade(5)
                      +",\n Total  : "+student.getTotal()          
                      +",\n Average: "+student.getAverage()+"\n"); 
  }
}

[steve souza]

Google "regular expression", and "java regular expression"

[Campbell Ritchie]

You will find details of regular expressions in the Java Tutorials.

And welcome to the Ranch