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Thread: Using set/get methods and arrays

  1. #1
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    Default Using set/get methods and arrays

    Hi guys, forgive me if breaking all sorts of laws in Java, I'm only a couple weeks into learning it and I've been struggling the whole way through. Right now what I was trying to do was create an array using the titles of five books and to test to see if my approach was working I tried to output the result. It seems like there's an error in my set/get methods. The code compiles, but my output is null.

    So my real question is, can I do what I'm trying to achieve? That is, pull array variables from set/get methods? Is there a better approach or would this work (note: I'm supposed to have get/set methods so those have to stay, I'm struggling with my constructors and arrays at the moment) I'll be working with this some more while I wait for a response so if I figure it out first I'll update with a solved tag and the code I end up using to do so, thanks!

    import java.util.Arrays;
     
    public class BookStore2 {
     
     
        public static void main(String[] args) {
     
            Book Book1 = new Book("978-0-7653-6264-3", "Wizard's First Rule", "Terry Goodkind", 1994, "Tom Doherty Associates, LLC", 7.99f);
            Book Book2 = new Book("0-812-54809-4", "Stone of Tears", "Terry Goodkind", 1995, "Tom Doherty Associates, LLC", 7.99f);
            Book Book3 = new Book("0-812-55147-8", "Blood of the Fold", "Terry Goodkind", 1995, "Tom Doherty Associates, LLC", 7.99f);
            Book Book4 = new Book("0-439-15411-1", "Dracula", "Bram Stroker", 1897, "Scholastic Inc", 4.99f);
            Book Book5 = new Book("0-440-94060-5", "I Am The Cheese", "Robert Cormier", 1977, "Dell Laurel-Leaf", 5.50f);
     
            String[] titleArray = new String[] {Book1.gettitle, Book2.gettitle, Book3.gettitle, Book4.gettitle, Book5.gettitle}; 
            System.out.println(Arrays.toString(titleArray));
     
        }
     
     
    }
     
     
    class Book{
     
      String ISBN;
      String title;
      String name;
      int year;
      String publisher;
      float price;
        String gettitle; // removed, this must have been part of the problem I was having
     
      public Book(String ISBN, String title, String name, int year, String publisher, float price){
          this.ISBN = ISBN;
          this.title = title;
          this.name = name;
          this.year = year;
          this.publisher = publisher;
          this.price = price;
      }
       public void setISBN(String ISBN){
           this.ISBN = ISBN;
       }
       String getISBN(){
           return ISBN;
       }
       public void settitle(String title){
           this.title = title;
       }
       String gettitle(){
           return title;
       }
       public void setname(String name){
           this.name = name;
       }
       String getname(){
           return name;
       }
       public void setyear(int year){
           this.year = year;
       }
       int getyear(){
           return year;
       }
       public void setpublisher(String publisher){
           this.publisher = publisher;
       }
      String getpublisher(){
          return publisher;
      }
       public void setprice(float price){
           this.price = price;
       }
       float getprice(){
           return price;
       }
       // list of getters
     
     
    } // end class book

    Updated code:

    import java.util.Arrays;
     
    public class BookStore2 {
     
     
        public static void main(String[] args) {
     
            Book book1 = new Book("978-0-7653-6264-3", "Wizard's First Rule", "Terry Goodkind", 1994, "Tom Doherty Associates, LLC", 7.99f);
            Book book2 = new Book("0-812-54809-4", "Stone of Tears", "Terry Goodkind", 1995, "Tom Doherty Associates, LLC", 7.99f);
            Book book3 = new Book("0-812-55147-8", "Blood of the Fold", "Terry Goodkind", 1995, "Tom Doherty Associates, LLC", 7.99f);
            Book book4 = new Book("0-439-15411-1", "Dracula", "Bram Stroker", 1897, "Scholastic Inc", 4.99f);
            Book book5 = new Book("0-440-94060-5", "I Am The Cheese", "Robert Cormier", 1977, "Dell Laurel-Leaf", 5.50f);
     
            String[] titleArray = new String[] {book1.gettitle(), book2.gettitle(), book3.gettitle(), book4.gettitle(), book5.gettitle()}; 
            System.out.println(Arrays.toString(titleArray));
            System.out.println(book1.gettitle());
     
        }
     
     
    }
     
     
    class Book{
     
      String ISBN;
      String title;
      String name;
      int year;
      String publisher;
      float price;
     
     
      public Book(String ISBN, String title, String name, int year, String publisher, float price){
          this.ISBN = ISBN;
          this.title = title;
          this.name = name;
          this.year = year;
          this.publisher = publisher;
          this.price = price;
      }
       public void setISBN(String ISBN){
           this.ISBN = ISBN;
       }
       String getISBN(){
           return ISBN;
       }
         String gettitle(){
           return title;
       }
       public void settitle(String title){
           this.title = title;
       }
       public void setname(String name){
           this.name = name;
       }
       String getname(){
           return name;
       }
       public void setyear(int year){
           this.year = year;
       }
       int getyear(){
           return year;
       }
       public void setpublisher(String publisher){
           this.publisher = publisher;
       }
      String getpublisher(){
          return publisher;
      }
       public void setprice(float price){
           this.price = price;
       }
       float getprice(){
           return price;
       }
       // list of getters
     
     
    } // end class book


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Using set/get methods and arrays

    my output is null.
    What variable are you printing that has a null value? Where do you give that variable a value so that it is not null? If you don't assign it a value it will keep the null default value.

    It is confusing to name a variable and a method with the same exact name. Can you change one of the names to make them unique?
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: Using set/get methods and arrays

    Okay, I found part of my problem, instead of writing this code:

     String[] titleArray = new String[] {Book1.gettitle, Book2.gettitle, Book3.gettitle, Book4.gettitle, Book5.gettitle}; 
            System.out.println(Arrays.toString(titleArray));
            System.out.println(Book1.gettitle);
    I changed it to:

        String[] titleArray = new String[] {Book1.title, Book2.title, Book3.title, Book4.title, Book5.title}; 
            System.out.println(Arrays.toString(titleArray));
            System.out.println(Book1.title);

    To answer your questions Norm, the variable I was trying to get to print is the title variable from my Book class. The variables should be assigned using the constructors that you see for Book1 - Book5.

    As for the second part of your question, I am uncertain what you mean by a variable and method with the same name maybe I am reading it wrong or understanding it wrong, but they appear to be all with different names?

    With the exclusion of, I found a duplicate gettitle line in my code near the beginning of the Book class, I removed that as I assume it was part of the problem.

    Edit: I see what you mean, you meant the variable gettitle and the method gettitle. Yeah, the variable for gettitle was not supposed to be there, it was removed once I found that it was there and then correcting the code to title instead of gettitle resulted in the correct output.

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Using set/get methods and arrays

    a variable and method with the same name
    See gettitle: It's a String and the name of a method,

    Where does the code use any of the get methods? It should use a method (book1.getTitle()) to access a class value and not access the class's variable directly like this: Book1.title

    Note: variable names should start with lowercase letters: book1 vs Book1
    If you don't understand my answer, don't ignore it, ask a question.

  5. The Following User Says Thank You to Norm For This Useful Post:

    Shadud (November 25th, 2012)

  6. #5
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    Default Re: Using set/get methods and arrays

    Quote Originally Posted by Norm View Post
    See gettitle: It's a String and the name of a method
    I removed the String already, as it was part of my confusion, that was the reason for producing a null value instead of a syntax error. I also made adjustments to the variable names to help readability and you pointed out the error that caused all of this to begin with. I wasn't understanding why it wasn't calling on the get methods, and it was because I left out the parenthesis (book1.gettitle()) at the end.

    I'll probably be asking for more help soon, this stuff gives me one heck of a headache.

    I will update the thread as solved, I don't think there is much that can be asked here and still remain on-topic.

    Thank you, Norm.

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