问题
Long story short (in Java):
String input= "0888880747;
long convert = Long.parseLong(input);
The value of convert is now: 888880747
How can I parse the String to a long but retain the leading zero?
回答1:
You cannot because a long does not have a leading zero. A long is supposed to store integers (the mathematical concept, not int), i.e.
A string of characters like 05 is not an integer, 5 is. What you can do is format a long that holds 5 with a leading zero when you print it, see e.g. java.util.Formatter.
Are you sure you even want to have a long/an integer? What do you want to do with it?
回答2:
You'll have to change it back to a String when you've done your calculations on convert, then:
output = String.format("%06d", convert);
回答3:
A long is a numeric value. The numeric value of 000001 is no different from 1: It's the exact same number.
So you can't find out how many leading zeroes the initial representation had, once you have a long.
And if you really care about that, then you shouldn't handle the input as a numeric type anyway, but store the String itself, instead.
回答4:
If your value is a long, then any zeroes to the left (leading) have no mathematical value, therefore, they are stripped off when you do the parsing.
来源：https://stackoverflow.com/questions/7918250/parse-string-to-long-with-leading-zero