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Thread: Why does OOP hate me so much- can not get my driver to work

  1. #1
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    Default Why does OOP hate me so much- can not get my driver to work

    Ok, so here is my class

    public class Student
    {
      private String name;  // student name
      private int id;       // student id
      //*********************************************************
      public void setName(String n)
      {
        this.name = n;
      }
      public void setId(int id)
      {
        this.id = id;
      }
      //*********************************************************
      public String getEmailAccount()
      {
        // Include "" in concatenation to convert to strings.
        return "" + this.name.charAt(0) + this.id +
          "@park.edu";
      }
      //*********************************************************
      public boolean isValid()
      {
        return this.id >= 100000 && this.id <= 999999;
      }
    } // end class Student

    Here is my driver
    import java.util.Scanner;
     
    public class StudentDriver
    {
      public static void main(String[] args)
      {
        Scanner stdIn = new Scanner(System.in);
        Student student;  // student object
        String name;      // student name
     
        // Instantiate Student object and assign it to student.
        student = new Student();
     
        System.out.print("Enter student name: ");
        name = stdIn.nextLine();
     
        // Assign name to the student object.
        student.setName();
     
        System.out.print("Enter student id: ");
        // In a single statement, read an int for the id value,
        // and assign it to the student object.
         name.setId()= stdIn.nextInt();
     
        // If invalid id, execute the loop.
        // (Use the isValid method in the while loop heading.)
        while (!isValid)
        {
          System.out.print("Invalid student id - reenter: ");
          // In a single statement, read an int for the id value
          // and assign it to the student object.
           student.SetId()= stdIn.nextInt();
        }
     
        System.out.println("\n" + name +
          ", your new e-mail account is: \n" +
          student.getEmailAccount());                   // Get email account.
      } // end main
    } // end class StudentDriver

    And here are my errors
    C:\Users\Jennifer\Documents\school\StudentDriver.java:18: error: method setName in class Student cannot be applied to given types;
        student.setName();
               ^
      required: String
      found: no arguments
      reason: actual and formal argument lists differ in length
    C:\Users\Jennifer\Documents\school\StudentDriver.java:23: error: cannot find symbol
         name.setId()= stdIn.nextInt();
             ^
      symbol:   method setId()
      location: variable name of type String
    C:\Users\Jennifer\Documents\school\StudentDriver.java:27: error: cannot find symbol
        while (!isValid)
                ^
      symbol:   variable isValid
      location: class StudentDriver
    C:\Users\Jennifer\Documents\school\StudentDriver.java:32: error: cannot find symbol
           student.SetId()= stdIn.nextInt();
                  ^
      symbol:   method SetId()
      location: variable student of type Student
    4 errors
     
    Tool completed with exit code 1

    I can't figure out what I'm doing wrong. The comments in the program are what I need to do and my attempt at the code is beneath them. My first issue is that I can't figure out how to set the name. I believe that I need to use the student variable name because that is what I'm trying to assign the name to. However, any way I try to modify the statement it doesn't work unless I go student.setName(name). Is that really the correct way to use the code? Doesn't that sort of negate the setName Method? Do I need to do the same with the setID?

    The boolean is giving me some issues. I want to do something like while(!student.isvalid()) but will that work with the student variable name?

    Hopefully I'm making some realtively simple errors, because this is driving me crazy...


  2. #2
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    Default Re: Why does OOP hate me so much- can not get my driver to work

    The setName() method requires an argument, a String, that provides the name:

    student.setName( "Sally" );

    Back away form a battle with OOP and "go with the flow." Look at the Student methods and realize what they require to be used. Also, consider the error message you posted that should have been very helpful:

    C:\Users\Jennifer\Documents\school\StudentDriver.j ava:18: error: method setName in class Student cannot be applied to given types;
    student.setName();
    ^
    required: String
    found: no arguments
    reason: actual and formal argument lists differ in length
    It's telling you that the method setName() requires a String but it didn't find one. Make sense?

  3. The Following User Says Thank You to GregBrannon For This Useful Post:

    kissyfurs (July 14th, 2013)

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    Default Re: Why does OOP hate me so much- can not get my driver to work

    So I can use student.setName (name) and that's correct? Isn't the purpose of the setName Method to set the name? Why do I have to have something in the parenthesis?

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    Default Re: Why does OOP hate me so much- can not get my driver to work

    You put something in the parentheses so that the setName() method knows what the student's name should be set to.

    Notice that the fact that you have a variable name in the main() method is neither here nor there to the compiler. It is not going to guess your intention and use name as the name you want for the student.

    I find that it's a good idea to document methods.

        /**
         * Sets the student's name to a given value.
         */
    public void setName(String n)
    {
        this.name = n;
    }

    In this case the comment makes it clear that the behaviour of setName() is to set the student's name to some value given when the method is called.

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    Default Re: Why does OOP hate me so much- can not get my driver to work

    I think I understand. I guess I was expecting the computer to do too much for me. I applied the corrections and updated my boolean according to my original post and it worked correctly, along with a few other changes. Thanks for your help.

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