CODEWITHSUNDEEP
javaoopsequence
user12951122
user12951122

Reputation:

oop java method to increment number sequentially

Im having an issue where I have to create a method in java to get a ticket number which every time it is called it generates a number sequentially.

this is what I have so far regarding the ticket method

public class Ticket
{
    public static final String PREFIX = "CAR";
    public static int number = 1000;

    //instance variables
    private String ticketNumber;

public Ticket(){
         ticketNumber = generateTicketNumber();
        }
public String getTicketNumber(){
        return ticketNumber;
    }

private String generateTicketNumber(){
        number = number++;
        ticketNumber = PREFIX +number;
        return ticketNumber;
    }

I'm told to use a static variable (which i have) to create and hold a counter to generate part of the ticket number, increment the static variable and assign it combined with the string prefix to the field ticketNumber. When i create an object it does not increment to CAR1001, it just goes CAR1000, am I to try a while loop for this?

Upvotes: 0

Views: 674

Answers (2)

kaya3
kaya3

Reputation: 51112

number = number++; is not evaluated how you think. What this actually does is that the right-hand side increments number, but number++ is also an expression whose value is the old value of number, before the increment is done. Then because of the number = ... assignment, that old value is assigned to number on the left-hand side, undoing the increment.

So you should just write number++; instead, which simply increments the variable.

Upvotes: 3

Elliott Frisch
Elliott Frisch

Reputation: 201497

Unless I'm missing something, I think you've over complicated this. All you need is PREFIX and number. Concatenate PREFIX with number and increment number. That can be done in one step like,

public class Ticket {
    private static final String PREFIX = "CAR";
    private static int number = 1000;

    public String getTicketNumber() {
        return PREFIX + number++;
    }
}

Or, perhaps a little easier to read,

public String getTicketNumber() {
    try {
        return PREFIX + number;
    } finally {
        number++;
    }
}

Upvotes: 1

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