Thread: Creating Random unused ID number for every library member.

Or can you please help me add 21 days to the loanDate as im struggling to do it..been trying for nearly 2 wks now. At least i would know how to do it next time..Have till Friday to submit this..Its a fail if I do not add the loan class..cheers

dateLoanDueBack.Date..........The dateLoanDueBack value should be 3 weeks from when the object is created(21 days)

trust me if i understood how to do it, then i would have by now...the API is so hard to understand it causes me more confusion than it solves. i could look at it all day and still not understand it...

Did you read my last post? You can't code anything that comes into your head. You must follow the rules as defined in the API.

The variable: Date does NOT exist in the GregorianCalendar class.

Yeeeeeeeeeeeeeeeeeeeeees done it. Its adding 21 days to the loanDate now..Here is it is..I ve capitalised DATE to diffrenciate it from the date method

/**
     * Constructor for objects of class Loan
     */
    public Loan(int bookId, int memberId)
    {
        // initialised fields.
        this.bookId = bookId;
        this.memberId = memberId;
        loanDate = new GregorianCalendar();
        dateLoanDueBack = new GregorianCalendar();
        dateLoanDueBack.add(dateLoanDueBack.DATE, 21);
 
    }

--- Update ---

now i ll try and add time to it.........

Originally Posted by Norm

Glad you got that one solved.


Java is case sensitive. Spelling it as written in the API doc will work better.

One confusing way you've coded the field arg is using a variable name instead of the name of the class.
The expected way of coding would be: Calendar.DATE

You are right, Wish I knew that yesterday..wud have saved me so much time...to do my documentation..

--- Update ---

more issues tho...when I print, it prints the book ID and member ID ok but not the loanDate or dateloanDueBack....gives me error message. "java.lang.illegalArgumentException:" cannot format given object as a Date(in java.text.DateFormat)

    /**
     * 
     * 
     */
    public void printLoanDetails()
    {
       System.out.println("Member ID:"  +  memberId);
       System.out.println("Book ID:"  +  bookId);
       DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
       System.out.println("Loan Date: "+dateFormat.format(loanDate));

This is the print method......Blue j wont let me to highlight and paste the error message so i ve written it as it is word for word..

--- Update ---

java.lang.IllegalArgumentException: Cannot format given Object as a Date
at java.text.DateFormat.format(DateFormat.java:301)
at java.text.Format.format(Format.java:157)
at Loan.printLoanDetails(Loan.java:92)
java.lang.IllegalArgumentException: Cannot format given Object as a Date
at java.text.DateFormat.format(DateFormat.java:301)
at java.text.Format.format(Format.java:157)
at Loan.printLoanDetails(Loan.java:92)
java.lang.IllegalArgumentException: Cannot format given Object as a Date
at java.text.DateFormat.format(DateFormat.java:301)
at java.text.Format.format(Format.java:157)
at Loan.printLoanDetails(Loan.java:92)

This is the message from the output window......

What type is loanDate?

its gregorian calendar

public String dateBookdueback(int bookID)
    {
      Loan.getLoanDate();
    }

My library is nearly done now....thanks to you......Got some issues here the above code, trying to call the getLoanDate from the library class but Im getting this error message "non-static method getLoanDate()cannot be referenced from a static context"

Originally Posted by Norm

You can not call a non-static method without using an instance of the class.

Loan.getLoanDate();

You need an instance of the Loan class to call the getLoanDate() method. It should be the instance that has the date in it.

Read the Class Methods section on this page: Understanding Instance and Class Members (The Java™ Tutorials > Learning the Java Language > Classes and Objects)

Just read the API documentation and still not sure how to call this method..Im running out of time to finish this work..I do know that non-static means that its not there. does not exist yet.

--- Update ---

Originally Posted by clarky2006

Just read the API documentation and still not sure how to call this method..Im running out of time to finish this work..I do know that non-static means that its not there. does not exist yet.

    public void returnDateLoanIsDueBack(int bookId)
    {
 
      Loan.loanReturnDate(loan);   
    }

now it cannot find symbol.............

    public String DateLoanIsDueBack(int bookId)
    {
      for(Loan loan : loans)
    {
          String dateReturned = "";  
          if(loan.getBookId() == bookId)
          {
           dateReturned = loan.getLoanReturnDate();
 
          }
    }
     dateReturned; 
    }

Hia this is how i ve coded that method but its not compiling..it says that dateReturned; is not a statement...

Originally Posted by Norm

The compiler is correct. A statement consisting only of a variable name is not valid.
What did you want to do with the value in the variable?

public String loanDate(int bookID)
    {
      String dateborrowed = "";
      for(Loan loan : loans)
      {
          if(loan.getBookId() == bookId)
          {
            dateborrowed = loan.getLoanDate();
        }
    }
    return dateborrowed;
    }

managed to re-write it and it works...here it is..

--- Update ---

But i do have problems with the return date, it seems to be fixed on 1/1/2013...i borrowed a book yesterday and the return date was 1/1/2013. i borrowed another today and was given the same return date 1/1/2013...its suppose to add 21 days each time but it doesnt.....here is the code.....

public class Loan
{
 
    // Declared fields for the Loan Class.
    private int bookId;// The book's unique ID.
    private int memberId;// The member's unique Identification number.
    public String month="";
    public String day="";
    public String year="";
    //private GregorianCalendar loanDate;// The date when loan was taken out.
    //private GregorianCalendar dateLoanDueBack;// The date when loan is due back.
    private String loanDate;
    private String loanReturnDate;
 
 
    /**
     * Default Constructor for objects of class Loan
     */
    public Loan()
    {
     int currentDay;
     int currentMonth;
     int currentYear;
     GregorianCalendar calendar = new GregorianCalendar();
     month=String.valueOf(calendar.get(GregorianCalendar.MONTH));            
     day=String.valueOf(calendar.get(GregorianCalendar.DAY_OF_MONTH));
     year=String.valueOf(calendar.get(GregorianCalendar.YEAR));
     loanDate = (day + " / " + month + " / " + year);
     //System.out.println (date);
     int d = Integer.parseInt(day);
     int m = Integer.parseInt(month);
     int y = Integer.parseInt(year);
     m = m + 1; 
     loanDate = (d + " / " + m + " / " + y);
     System.out.println ("Loan Date: - " + loanDate);
     d = d + 21;
     if (d > 30)
     {
         d= 1;
         m = m + 1;
        }
     if (m > 12)
     {
        m = 1; 
        y = y + 1;
        }
     currentMonth = m;
     currentYear = y;
     currentDay = d;
     loanReturnDate = (currentDay + "/" + currentMonth + "/" + currentYear);
     System.out.println ("Loan Return date - " + loanReturnDate);
    }

Originally Posted by Norm

The posted code does not compile. One problem is missing import statements.

Another problem is there is no code to test the Loan class. There needs to be a small class with a main() method that calls the Loan class and shows the problem. It needs to compile, execute and show the problem.

it does compile in blue J..u dont need main method in blue J..i ve just compiled it again and it says no syntax errors..

--- Update ---

import java.util.*;
import java.text.*;
 
/**
 * This Class would hold all loan details.
 * 
 * @author () 
 * @version 1.0
 */
public class Loan
{
 
    // Declared fields for the Loan Class.
    private int bookId;// The book's unique ID.
    private int memberId;// The member's unique Identification number.
    public String month="";
    public String day="";
    public String year="";
    //private GregorianCalendar loanDate;// The date when loan was taken out.
    //private GregorianCalendar dateLoanDueBack;// The date when loan is due back.
    private String loanDate;
    private String loanReturnDate;
 
 
    /**
     * Default Constructor for objects of class Loan
     */
    public Loan()
    {
     int currentDay;
     int currentMonth;
     int currentYear;
     GregorianCalendar calendar = new GregorianCalendar();
     month=String.valueOf(calendar.get(GregorianCalendar.MONTH));            
     day=String.valueOf(calendar.get(GregorianCalendar.DAY_OF_MONTH));
     year=String.valueOf(calendar.get(GregorianCalendar.YEAR));
     loanDate = (day + " / " + month + " / " + year);
     //System.out.println (date);
     int d = Integer.parseInt(day);
     int m = Integer.parseInt(month);
     int y = Integer.parseInt(year);
     m = m + 1; 
     loanDate = (d + " / " + m + " / " + y);
     System.out.println ("Loan Date: - " + loanDate);
     d = d + 21;
     if (d > 30)
     {
         d= 1;
         m = m + 1;
        }
     if (m > 12)
     {
        m = 1; 
        y = y + 1;
        }
     currentMonth = m;
     currentYear = y;
     currentDay = d;
     loanReturnDate = (currentDay + "/" + currentMonth + "/" + currentYear);
     System.out.println ("Loan Return date - " + loanReturnDate);
    }

It does have import statememnt...

--- Update ---

I ve tried to create a test class but I ve not been able to do so..im not that clever yet with java..

Originally Posted by Norm

There is no main() method in the class so there is no way to execute it for testing.
There needs to be code that executes and shows the problem for testing.



Where does the code call the add() method with 21 days?

d = d + 21;
     if (d > 30)
     {
         d= 1;
         m = m + 1;
     }
     if (m > 12)
     {
        m = 1; 
        y = y + 1;
     }

this is suppose to add 21 days