How to convert String to Long without losing leading zero [duplicate]

Answer 1

You don't, a Long / long / Integer / int is a number, a number does not having leading zeros. Only a string representation of a number may have leading zeros.

If you absolutely need the leading zeros and the number 0001 is different from 001 then you are not dealing with numbers but just with strings that look like numbers and you should not convert it to a long in the first place.

Answer 2

You cannot because a Long does not have a leading zero.

You can store it with String like this String.format("%02d", longValue);

Answer 3

A long cannot have lead value as 0. I don't know about your use case but if you want to have 00 as lead don't convert it back to long, use String instead.