将字符串解析为带前导零的 long

Question

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?

Answer 1

You cannot because a long does not have a leading zero. A long is supposed to store integers (the mathematical concept, not int ) , ie

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 eg java.util.Formatter .

Are you sure you even want to have a long/an integer? What do you want to do with it?

Answer 2

完成转换计算后，您必须将其改回String ，然后：

output = String.format("%06d", convert);

Answer 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.

Answer 4

You can tweak the code. First get the length of string.

String input  =   "0888880747";

System.out.println(String.format("%0"+input.length()+"d", Long.valueOf(input)))):

The above tweek works but doesn't look good. Better to read the value as String and store in DB as varchar instead of Number if leading zeros matter.

Answer 5

如果您的值是 long，则左侧（前导）的任何零都没有数学价值，因此，在您进行解析时，它们会被剥离。