How to keep leading zero when storing integer value with leading zero in Arraylist without using String?

Question

I wish to store some phone number in arraylist and if the number contain leading zero ,i want to store in arraylist as it is, without removing leading zero. how can i achieve that .

ArrayList<Integer> Restrict = new ArrayList<Integer>();
cars.add(01);
cars.add(02);
cars.add(3);
cars.add(4);
System.out.println(cars.get(0));

output

how can i get 01 instead of 1.

Integers don't store any leading zeros, as only the actual integer value is stored. But when printing, you could pad the resulting string like shown here: https://stackoverflow.com/questions/473282/how-can-i-pad-an-integer-with-zeros-on-the-left — maloomeister, Nov 20 '20 at 11:17
@maloomeister How would you know not to pad 3 and 4? You can't — Michael, Nov 20 '20 at 11:18
@Michael of course, you are right. They would have to know which numbers to pad himself. I just showed him a way to pad his integers, how they use that knowledge is not my worry. — maloomeister, Nov 20 '20 at 11:21
Only possible by storing them as `String` or format them in your output using `String.format("%02d", myNum)` — goldthelocks, Nov 20 '20 at 11:21
i wish to know if i can store as integer with leading zero .. storing as string is not an option .for me — tomtom, Nov 20 '20 at 11:30

score 3 · Answer 1 · answered Nov 20 '20 at 11:20

3

You can store them as strings

ArrayList<String> Restrict = new ArrayList<>();
        cars.add("01");
        cars.add("02");
        cars.add("3");
        cars.add("4");

    System.out.println(cars.get(0));

answered Nov 20 '20 at 11:20

fatma zehra güç

164
5

score 1 · Answer 2 · answered Nov 20 '20 at 11:35

`Integer` is the wrong type for this requirement

A phone number consists of a minimum of 10 digits (first digit from 1-9) and it can go well beyond the maximum limit of Integer which is 2147483647.

Apart from this, the 0 at the beginning of an Integer means it's radix is 8 i.e. it represents an octal number e.g.

public class Main {
    public static void main(String[] args) {
        int x = 0123;
        System.out.println(x);
    }
}

Output:

Note that (0123)₈ = (83)₁₀

The right type for this requirement is String i.e. you should declare your List as follows:

List<String> restrict = new ArrayList<>();

and store the numbers as

restrict.add("01234567890")
restrict.add("1234567890")

Also, always follow the Java naming conventions e.g. the name of the variable can be restrict but should not be named as Restrict (as in your code).

While this is a good answer, I can't help but feel your effort is misplaced — Michael, Nov 20 '20 at 11:36
@Michael - Thanks for the feedback. No worries, I posted it anyway because I was half-way while this was closed. If it can be helpful for anyone, that's the best reward I will have for this effort. — Arvind Kumar Avinash, Nov 20 '20 at 11:39

How to keep leading zero when storing integer value with leading zero in Arraylist without using String?

2 Answers2

Integer is the wrong type for this requirement

`Integer` is the wrong type for this requirement