Error when trying to delete a row from a text file by entering a parameter? | Smarter Dev | Page 1

ebon kelpBOT Apr 25, 2023, 12:24 PM

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@silk plinth

kmusial46 Uploaded Some Code

I have attached a screenshot of the error can anyone help?

Uploaded these files to a Gist

message.txt

View The Gist

silk plinth Apr 25, 2023, 12:24 PM

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opaque monolith Apr 25, 2023, 12:51 PM

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Looking at line 273 on the file you sent, it doesn't have equalsIgnoreCase(), weird

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But I can tell you that the problem is you never put anything inside students. You're comparing students[i], but you never set that index of the array

silk plinth Apr 25, 2023, 1:01 PM

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just realised that the lines are wrong as i have comments at the top

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public static void deleteStudent(Scanner scanner) {
if (numberOfStudents == 0) {
System.out.println("There are no students to delete.");
}

System.out.println("Enter the name of the student you wish to delete: ");
String studentDelete = scanner.nextLine().trim();
boolean studentDeleted = false;
for (int i = 0; i < numberOfStudents; i++) {
    if (students[i].name.equalsIgnoreCase(studentDelete)) {
        for (int j = i; j < numberOfStudents - 1; j++) {
            students[j] = students[j + 1];
        }
        numberOfStudents--;
        studentDeleted = true;
        System.out.println("Student has been deleted successfully.");
        break;
    }
}
if (!studentDeleted) {
    System.out.println("Student not found.");
}

}

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line 273 is if (students[i].name.equalsIgnoreCase(studentDelete)) {

silk plinth Apr 25, 2023, 1:04 PM

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opaque monolith But I can tell you that the problem is you never put anything inside `students`....

not sure i understand

opaque monolith Apr 25, 2023, 1:20 PM

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I'll explain later, but first I'm confused here: ```java
while ((line1 = courseReader.readLine()) != null) {
String[] parts = line1.split(",");
String courseName = parts[0];
int studentFT = Integer.parseInt(parts[1]);
int studentPT = Integer.parseInt(parts[2]);
double totalFeesPaid = Double.parseDouble(parts[3]);
}
courseReader.close();

This part of your `loadDetails()` method doesn't do anything with those parts...

silk plinth Apr 25, 2023, 1:22 PM

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should i create a constructor with these in it?

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sorry im not that experienced in java 😅

opaque monolith Apr 25, 2023, 1:23 PM

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Well, what is it supposed to do with that information?

silk plinth Apr 25, 2023, 1:24 PM

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well studentft/pt is used for the report method

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course name is final

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and the fees is the tuition fees added from all the students

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im just supposed to store that in the file

opaque monolith Apr 25, 2023, 1:30 PM

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In the file you're reading it from? It's already in that file

silk plinth Apr 25, 2023, 1:33 PM

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not sure i follow when i add a student the file is updated with either ft/pt and the fees are added on

opaque monolith Apr 25, 2023, 1:36 PM

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Oh wait, why is your Student constructor empty? The one that accepts a String for dob

opaque monolith Apr 25, 2023, 1:37 PM

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silk plinth not sure i understand

Also you're right, sorry I just double checked and the student does exist, but not it's name

silk plinth Apr 25, 2023, 1:38 PM

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yea adding the student works and so does updating both files its just deleting it is what is throwing me an error

opaque monolith Apr 25, 2023, 1:39 PM

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silk plinth

When you ran the program here, did you ever add students manually or only read from the file?

silk plinth Apr 25, 2023, 1:40 PM

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i added a student which worked fine and i tried to delete the same one afterwards

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just randomly got this error now?

opaque monolith Apr 25, 2023, 1:50 PM

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Weird. After you define parts, print out line and parts.length so we can see what's up

silk plinth Apr 25, 2023, 1:51 PM

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do you mean inbetween string[] and string name?

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or after double tuitionFee?

opaque monolith Apr 25, 2023, 1:52 PM

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After the line String[] parts = line.split(",");
Add 2 new lines for printing out those variables. I'm just experimenting here

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So yes

silk plinth Apr 25, 2023, 1:53 PM

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not sure if thats what you mean

opaque monolith Apr 25, 2023, 1:54 PM

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I meant to print line, not parts

silk plinth Apr 25, 2023, 1:54 PM

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so just replace parts with line yes?

opaque monolith Apr 25, 2023, 1:55 PM

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Yes

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We're doing this so we can see what the line looks like, so we know why parts is only reading one part

silk plinth Apr 25, 2023, 1:55 PM

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yes i understand now

opaque monolith Apr 25, 2023, 1:56 PM

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Ah, so the problem is there's an extra blank line

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In the file

silk plinth Apr 25, 2023, 1:56 PM

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oh right yes

opaque monolith Apr 25, 2023, 1:57 PM

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You can remove the prints now

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Does fixing the file fix that?

silk plinth Apr 25, 2023, 1:57 PM

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yes

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deleting still doesnt work though

opaque monolith Apr 25, 2023, 1:58 PM

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opaque monolith Oh wait, why is your Student constructor empty? The one that accepts a String fo...

Did you ever fix this

silk plinth Apr 25, 2023, 1:59 PM

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no not sure what to do

opaque monolith Apr 25, 2023, 2:02 PM

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The same thing as the other constructor, but turn the string into a Date first

silk plinth Apr 25, 2023, 2:03 PM

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i have a constructor for a new student just above that with the date format

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not sure why i have 2

opaque monolith Apr 25, 2023, 2:03 PM

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Oh

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Wait, you have the one for a Date dob, but the String dob is empty

silk plinth Apr 25, 2023, 2:04 PM

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yes

opaque monolith Apr 25, 2023, 2:05 PM

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loadDetails() uses the String dob constructor, which currently creates an empty Student

silk plinth Apr 25, 2023, 2:05 PM

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so will i change that to date?

opaque monolith Apr 25, 2023, 2:07 PM

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That would be easier. Assuming you mean inside loadDetails()

silk plinth Apr 25, 2023, 2:07 PM

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yes

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its prompting me to change it back to string?

opaque monolith Apr 25, 2023, 2:08 PM

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wdym?

silk plinth Apr 25, 2023, 2:08 PM

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opaque monolith Apr 25, 2023, 2:09 PM

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Oh, why are you doing that? I meant change it to a Date object using the formatter as before

silk plinth Apr 25, 2023, 2:09 PM

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not sure im following

opaque monolith Apr 25, 2023, 2:15 PM

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String dateOfBirth = parts[1];

SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
Date dob;
try {
  dob = dateFormat.parse(dateOfBirth);
}
catch (ParseException e) {
  System.out.println("Error reading file");
  return;
}

silk plinth Apr 25, 2023, 2:16 PM

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oh right yes sorry i thought u meant earlier in the chat

opaque monolith Apr 25, 2023, 2:16 PM

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No worries

silk plinth Apr 25, 2023, 2:17 PM

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this is what happens when i try to run it now

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this is highlighted in red

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its prompting me to create a constructor

opaque monolith Apr 25, 2023, 2:18 PM

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I'm assuming you deleted the empty String dob constructor? Anyway, you're supposed to use a Date, like the one we created, not the string

opaque monolith Apr 25, 2023, 2:19 PM

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opaque monolith ```java String dateOfBirth = parts[1]; SimpleDateFormat dateFormat = new Simple...

So after doing this use dob instead of dateOfBirth when creating the student

silk plinth Apr 25, 2023, 2:21 PM

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yes i deleted the empty one so do i change dateOfBirth to dob in the loadDetails method?

opaque monolith Apr 25, 2023, 2:21 PM

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Only inside the new Student()

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But yes

silk plinth Apr 25, 2023, 2:21 PM

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yes and what about the tuitionFee?

opaque monolith Apr 25, 2023, 2:22 PM

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Hm, whats it say when you click it?

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Or hover

silk plinth Apr 25, 2023, 2:23 PM

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think i got it, it wasnt in the constructor at the start but it is greyed out

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when i put it in

opaque monolith Apr 25, 2023, 2:23 PM

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Yep, just saw that

silk plinth Apr 25, 2023, 2:24 PM

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but now this is what im getting in the addStudent method prompting me to remove it

opaque monolith Apr 25, 2023, 2:29 PM

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Add the tuition fee back to the new student()

silk plinth Apr 25, 2023, 2:30 PM

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telling me to create a local variable?

opaque monolith Apr 25, 2023, 2:31 PM

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Did you remove the variable?

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parts[6] right?

silk plinth Apr 25, 2023, 2:32 PM

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from loadDetails?

opaque monolith Apr 25, 2023, 2:32 PM

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Yes

silk plinth Apr 25, 2023, 2:33 PM

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did it there now also had to remove it from the constructor under it and the one at the start

opaque monolith Apr 25, 2023, 2:34 PM

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You should have it in both the constructor and new student(), or neither. That's what matters

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If it's in one, put it in the other

silk plinth Apr 25, 2023, 2:35 PM

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yes i understand now thank you

opaque monolith Apr 25, 2023, 2:36 PM

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👍

silk plinth Apr 25, 2023, 2:36 PM

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just seeing now when i try to add another student it overwrites the first one and the date is just a series of numbers?

opaque monolith Apr 25, 2023, 2:39 PM

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Using loadDetails?

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Sorry I have to go to class rn, I'll be back in an hour or two

silk plinth Apr 25, 2023, 2:40 PM

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yea thats ok dont worry

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its when im saving it so saveDetails

opaque monolith Apr 25, 2023, 6:54 PM

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silk plinth just seeing now when i try to add another student it overwrites the first one an...

What do you mean by that last part?

silk plinth Apr 25, 2023, 8:35 PM

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this is what happens when i add a student and save it

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the long number is supposed to be a date

opaque monolith Apr 25, 2023, 8:46 PM

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Try using dob.toString() + "," instead

silk plinth Apr 25, 2023, 8:47 PM

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yep that sorted it thanks

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still overwriting the first student though

opaque monolith Apr 25, 2023, 9:56 PM

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I'm home now so I can look into it

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@silk plinth could you re-upload your code here? Just because we edited it a bit

ebon kelpBOT Apr 26, 2023, 10:03 AM

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@silk plinth

kmusial46 Uploaded Some Code

Uploaded these files to a Gist

message.txt

View The Gist

silk plinth Apr 26, 2023, 10:03 AM

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sorry just seeing this now uploaded the code there

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im having an error reading the file for some reason

#Error when trying to delete a row from a text file by entering a parameter?