问题
I'm trying to figure out why String.format() is behaving the way it does.
Context: Systems programming class, writing an assembler.
There is a 5 character hex field in the object file, which I am creating from a value.
Tried using: String.format("%05X", decInt);
This works as intended for positive numbers
(11 -> 0000B)
However it fails for negative numbers
(-1 -> FFFFFFFF instead of FFFFF)
I suppose I could just take a substring of the last 5 characters, but I would still like to figure out why it behaves this way.
回答1:
The width used in format is always a minimum width. In this case, instead of using sub string operations I would suggest:
String.format("%05X", decInt & 0xFFFFF);
回答2:
Format width only works to create a minimum number of digits, and only has effect on leading zeroes.
Instead of substring, you could use a bit mask:
String.format("%05X", decInt & 0x0FFFFF)
By the way, 11 -> 0000B, not 0000A as claimed in your question.
来源：https://stackoverflow.com/questions/9610254/string-format-and-hex-numbers-in-java