CODEWITHSUNDEEP
javanumbers
JDN
JDN

Reputation: 519

How do I put together numbers in java?

For some reason when I run the following code the program prints out "JDN4" or "JDN16" when at all times I want it to be printing "JDN" followed by three numbers ranging from 0-9; for example, "JDN123" or "JDN045" or "JDN206". What is wrong with the code?

import java.util.*;

public class Document2 {
    public static void main(String[] args) {
        String initials = "JDN";
        int randomNumbers;
        Random generator = new Random();
        int randomNumber1 = generator.nextInt(9);
        int randomNumber2 = generator.nextInt(9);
        int randomNumber3 = generator.nextInt(9);
        randomNumbers = randomNumber1 + randomNumber2 + randomNumber3;
        String userName = initials + randomNumbers;
        System.out.println("Your username is " + userName +  ".");
    }
}

Upvotes: 1

Views: 3132

Answers (7)

JB Nizet
JB Nizet

Reputation: 691755

What's wrong is that the + operator does an addition, and not a concatenation when used on int variables.

Use 

String randomNumbers = Integer.toString(randomNumber1) + Integer.toString(randomNumber2) + Integer.toString(randomNumber3);

to convert the numbers into strings and concatenate them.

Upvotes: 1

NullUserException
NullUserException

Reputation: 85468

Your problem is randomNumbers is declared as an int, so when you use the + on the other ints, it will sum the integers rather than concatenate them.

So, if we were to use your approach, we'd need a string:

String userName = initials + randomNumber1 + randomNumber2 + randomNumber3;

But it would be a lot easier just to generate a number from 0-999 and pad it with zeroes:

int randomNumber = generator.nextInt(1000);
String usernName = initials + String.format("%03d", randomNumber);

Something else worth noting is that Random.nextInt(n) generates a random number between 0 (inclusive) and n (exclusive), so you probably should be doing .nextInt(10) if you want a number between 0 and 9.

Upvotes: 6

KV Prajapati
KV Prajapati

Reputation: 94645

Try,

String userName=String.format("%s%d%d%d",initials,randomNumber1,randomNumber2,randomNumber3);

Upvotes: 3

K-ballo
K-ballo

Reputation: 81349

You are adding three digits, that would at most give you 27. You want to concatenate the string representation of those digits.

That said, why don't you simply generate a random number between 0 and 999?

Upvotes: 0

Jordonias
Jordonias

Reputation: 5848

You are adding the numbers here.

randomNumbers = randomNumber1 + randomNumber2 + randomNumber3;

If you want to achieve what you are looking for using this same method you could do.

randomNumbers = randomNumber1 + (randomNumber2 * 10) + (randomNumber3 * 100);

Upvotes: 1

C. K. Young
C. K. Young

Reputation: 223033

Suppose you have three numbers:

int randomNumber1 = 3;
int randomNumber2 = 4;
int randomNumber3 = 5;
int randomNumbers = randomNumber1 + randomNumber2 + randomNumber3;

Do you expect randomNumbers to be 345? Or do you expect it to be 12?

Now try this:

String randomNumbers = "" + randomNumber1 + randomNumber2 + randomNumber3;

What do you get this time?

Upvotes: 3

Vicente Plata
Vicente Plata

Reputation: 3380

randomNumbers = randomNumber1 + randomNumber2 + randomNumber3;

You're adding the numbers, not concatenating them.

Suggested solution: use only 1 random number with 

generator.nextInt(1000);

Or, you can go like:

String userName = initials + randomNumer1 + randomNumber2 + randomNumber3;

But I'm nearly sure you'll get 2 or even 3 times the same number, so you should use the first approach instead.

Upvotes: 2

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