Create several new objects within a for-loop in Java

Question

I want to create several objects from a class in a for loop. but I don't know how to code it. What I have written creates a new object but it overwrites the previous object.

package assginment1_version4;

import java.util.*;

public class Client {

public static void main (String[] args) {
    System.out.println ("this is a bill database");
    System.out.println ("add a user?(Y/N)");

    Scanner input = new Scanner(System.in);
    String answer = input.nextLine ();
    ArrayList ary = new ArrayList ();

    for (int i=1 ; i < 100; i++) {
        if (answer.equalsIgnoreCase("y")) {
            Bill bill1 = new Bill();
            System.out.println("user first name:");
            bill1.setFname (input.nextLine());
            System.out.println("user Last name:");
            bill1.setLname (input.nextLine());
            System.out.println ("add a user?(Y/N)");
            answer = input.nextLine ();
        } else if (answer.equalsIgnoreCase ("n")) {
            if (Bill.getBillCounter () == 0) {
                System.out.println ("the Database is empty");
                break;
            } else {
                System.out.println ("Number of Users:  "
                        + Bill.getBillCounter ());
                break;
            }
        } else {
            while (!answer.equalsIgnoreCase ("n")
                    && !answer.equalsIgnoreCase ("y")) {
                System.out.println ("add a user?(Y/N)");
                answer = input.nextLine ();
                }
            }
        }
    }
}

please help me to complete this code.

I want to add new objects (bill2, bill3,...) to this database, but my code writes the new object over the previous one.I want to keep all objects information in my database. — msc87
– msc87, Commented May 10, 2012 at 22:17
@msc87 It is helpful if you mark the answer that helped solve the problem as the accepted answer (plus you get 2 karma)! — jbranchaud
– jbranchaud, Commented Jun 7, 2012 at 18:22

Dan W · Accepted Answer · 2012-05-10 22:11:35Z

7

You're overriding them because you create a new Bill on each loop and never save them off anywhere. I believe you want to add them to your ArrayList:

First, you should add a type to your ArrayList:

ArrayList<Bill> ary = new ArrayList<Bill>();

Then, before you get the input from the user on whether or not to add a new Bill, you should add the current one to this list:

...
System.out.println("user Last name:");
bill1.setLname(input.nextLine());
ary.add(bill1);
...

answered May 10, 2012 at 22:11

Dan W

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5 Comments

msc87 Over a year ago

did what you suggested and now I can save new objects but there is anther problem....I cannot retrieve the objects' information. for example; System.out.println(bill1.getFname(ary.get(index)))

Alexis King Over a year ago

@msc87 Use ary.get(index).getFname() instead (though I can't be sure without seeing the Bill class information.

msc87 Over a year ago

I put the the Bill class here and I did what you said but it returns this error: Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 1, Size: 1 at java.util.ArrayList.RangeCheck(Unknown Source) at java.util.ArrayList.get(Unknown Source) at assginment1_version2.Client.main(Client.java:46)

Dan W Over a year ago

@msc87 Since this is a new problem, you should either, accept an answer and then ask a new question for this new problem or edit your original question with your new problem. Also, when updating, don't post as an answer, you should edit your original question.

Dan W Over a year ago

@msc87 Arrays are 0 based in java. If the length of your arraylist is 1, then you get Bill by: ary.get(0).getFname().

Marcos · Accepted Answer · 2012-05-10 22:11:34Z

1

You haven't used the ArrayList, you need to add the Bill's objects at the end of the for loop.

ary.add(bill1);

and add a type to your ArrayList

ArrayList<Bill> ary = new ArrayList<Bill>();

answered May 10, 2012 at 22:11

Marcos

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Comments

Mike Edward Moras · Accepted Answer · 2013-12-02 12:26:11Z

This is the Bill class.....

package assginment1_version2;

public class Bill {

/**
 *  Attributes of a bill
 */
private String firstName;
private String lastName;
private int paymentDeadline;
private int paymentCode;
private int billCode;

/**
* Attribute of Bill Class
*/

      private static int BillCounter=0;

/**
 *  Methods of Bill class
 * @return number of users
 */
/*public static int getBillCounter(){
    return BillCounter;
}*/


/**
 * Class Constructor
 * @param Fname is the first name of user
 * @param Lname is the last name of user
 * @param Pdeadline is the deadline of paying the bill
 * @param Pcode introduces the payment uniquely 
 * @param Bcode introduces the bill uniquely
 */
    public Bill (){
        BillCounter++;
    }

/**
 *  FirstName methods 
 *  method to set FirstName
 * @param n is the input of setname method as a user name
 */
public void setFname (String n){
    firstName=n;
}
// method to get FirstName
public String getFname (){
    return firstName;
}


/**
 *  LastName methods
 *  method to set LastName
 */
public void setLname (String m){
    lastName=m;
}
// method to get LastName 
public String getLname(){
    return lastName;
}


/**
 * PaymentDeadline methods
 * method to set PaymentDeadline     
 */
public void setPaymentDeadline(int m){
    paymentDeadline= m;
}
//method to get PaymentDeadline
public int getPaymentDeadline(){
    return paymentDeadline;
}

/*
 * PaymentCode methods
 * Method to set PaymentCode
 */
public void setPaymentCode (int m){
    paymentCode=m;
}
//method to get PaymentCode
public int getPaymentCode(){
    return paymentCode;
}

/*
 * Methods of BillCode
 * method to set BillCode 
 */
public void setBcode(int Bcode){
    billCode=Bcode;
}
//method to get BillCode
public int getBcode(){
    return billCode;
}
}

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