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Thread: Need help using JOptionPane/entering valid id#

  1. #1
    Junior Member javaNewbie2014's Avatar
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    Default Need help using JOptionPane/entering valid id#

    I am working on allowing a user to enter an ID # using JOptionPane. If the ID is valid, then it will display the ID#, student name, and GPA. If it is not valid, then the window should pop up again to allow the user to enter a valid ID. I have managed to get that far.

    I am struggling with once a valid ID # is entered, how do I get the loop to stop? I have tried several different ways, but the code below is the most recent one, and it is still not working! Any help/suggestions to try would be greatly appreciated.

    import javax.swing.*;
    public class StudentIDArray
    {
       public static void main(String[] args)
       {
          String enteredID;
          int idNumber;
          int x = 0; 
          String studentName = "";
          double studentGPA = 0.0; 
          boolean validID = false;
     
          int[] id = {1001, 1002, 1003, 1004, 1005, 1006, 1007, 1008, 1009, 1010};
          String[] names = {"Bob", "Joe", "Fred", "Suzie", "Jane", "Megan", "Frank", "Jill", "Tom", "Judy"};
          double[] gpa = {3.5, 3.32, 3.7, 4.0, 3.72, 3.93, 2.6, 1.95, 2.18, 2.83};
     
          enteredID = JOptionPane.showInputDialog(null, "Enter a four-digit student ID number");
          idNumber = Integer.parseInt(enteredID);
     
          for(x = 0; x < id.length; ++x)
          {
             if(idNumber == id[x])
             {
                validID = true;
                studentName = names[x];
                studentGPA = gpa[x];
             }
          }
     
          if(validID == false)
             JOptionPane.showMessageDialog(null, "You entered an invalid ID number");
          else                   
             JOptionPane.showMessageDialog(null, "You entered " + idNumber + ".\nThe student's name is "
                + studentName + " and the GPA is " + studentGPA);                
       }
    }


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Need help using JOptionPane/entering valid id#

    how do I get the loop to stop?
    What loop is giving you problems? The for loop should end ok.
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
    Junior Member javaNewbie2014's Avatar
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    Default Re: Need help using JOptionPane/entering valid id#

    Quote Originally Posted by Norm View Post
    What loop is giving you problems? The for loop should end ok.
    It would help if I checked that I posted the correct code that shows the issue!

    Once an invalid ID # is entered, I can't figure out how to get it to switch to validID = true, and move on with displaying the student's name and GPA. For example, when I enter 1234, it shows an error and asks me to enter another ID number. I enter 1005 (which is on the list of Student ID #'s), it still shows as an error and want me to enter another number. It keeps doing that until I close it.

    while(validID == false)
          {
             enteredID = JOptionPane.showInputDialog(null,"You entered an invalid ID number.  Please enter a student ID #");
             idNumber = Integer.parseInt(enteredID);
             for(x = 0; x < id.length; ++x)
             {
                if(idNumber == id[x])
                {
                   validID = true;
                   studentName = names[x];
                   studentGPA = gpa[x];
                }
                else
                   validID = false;
             }
          }

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Need help using JOptionPane/entering valid id#

    Is it possible the value of validID can be set true and then later in the loop it can be set false?
    Once a true is found, the code should exit the loop.
    A couple of ways to do that:
    use the break statement
    include a test of the value of validID in the for loops termination condition.
    If you don't understand my answer, don't ignore it, ask a question.

  5. #5
    Junior Member javaNewbie2014's Avatar
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    Default Re: Need help using JOptionPane/entering valid id#

    Thanks for the feedback. I tried a couple different ways like you mentioned, but I'm wondering if I am not putting the information in the correct place.

    When I used just the break statement, it let me enter a new ID # the second time, but regardless of what I entered, it kicked it out and left the name & GPA as the default values. I tried putting the break statement in a couple different places, but none of them were making it work the way I want it to work. I'm just confused on what would be causing the validID to change back to false after I enter a valid ID #, and cause the loop to continue to execute.

    for(x = 0; x < id.length && validID == false; ++x)
          {
             if(idNumber != id[x])
             {
                validID = false;
                enteredID = JOptionPane.showInputDialog(null,"You entered an invalid ID number.  Please enter a student ID #");
                idNumber = Integer.parseInt(enteredID);
             }
             else
             {
                studentName = names[x];
                studentGPA = gpa[x];
                validID = true;
                break;
             }
          }

  6. #6
    Super Moderator Norm's Avatar
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    Default Re: Need help using JOptionPane/entering valid id#

    Do you need to tell the user something for every item in the array that you look at that does not match?
    Would it be better to wait until all the elements in the array had been looked at before telling the user that his entry was not in the array? See post#3
    If you don't understand my answer, don't ignore it, ask a question.

  7. #7
    Junior Member javaNewbie2014's Avatar
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    Default Re: Need help using JOptionPane/entering valid id#

    I changed it back to the way I had it in post #3. I made the while statement separate and searched through the array, and it worked! Thanks so much for your help!!

  8. #8
    Super Moderator Norm's Avatar
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    Default Re: Need help using JOptionPane/entering valid id#

    Glad you got it working.
    If you don't understand my answer, don't ignore it, ask a question.

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