Signed Hexadecimal to decimal in Java

Question

I was wondering if it's possible to convert a signed Hexadecimal (negative) to its corresponding decimal value.

• Eran: Assuming your input is a String starting in '-' and containing only hex digits, Integer.parseInt(input,16) will work.
• Nicolas Filotto: show us what you have so far
• Jujumancer: What I am doing right now is that I take the negative hex and convert it to binary. I have a 2's compliment binary to decimal. It does work on small values. But when I try to convert large values like -4000(assuming hex) it is not correct.

Answer 1

I assume that you have a hexadecimal value in form of a String.

The method parseInt(String s, int radix) can take a hexadecimal (signed) String and with the proper radix (16) it will parse it to an Integer.

int decimalInt = parseInt(hexaStr, 16);

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the solution above only works if you have numbers like -FFAA07BB... if you want the Two's complements you'll have to convert it yourself.

String hex = "F0BDC0";
// First convert the Hex-number into a binary number:
String bin = Integer.toString(Integer.parseInt(hex, 16), 2);
// Now create the complement (make 1's to 0's and vice versa)
String binCompl = bin.replace('0', 'X').replace('1', '0').replace('X', '1');
// Now parse it back to an integer, add 1 and make it negative:
int result = (Integer.parseInt(binCompl, 2) + 1) * -1;

or if you feel like having a one-liner:

int result = (Integer.parseInt(Integer.toString(Integer.parseInt("F0BDC0", 16), 2).replace('0', 'X').replace('1', '0').replace('X', '1'), 2) + 1) * -1;

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If the numbers get so big (or small), that an Integer will have an overflow, use Long.toString(...) and Long.parseLong(...) instead.

• Jujumancer: I tried it and unfortunately, it returns an unsigned integer(15777216). My hex value is "F0BDC0" which should be -1000000.
• ParkerHalo: @Jujumancer I've edited my post... that self-made solution should work for you... But be careful this solution treats every number as a negative number, even if it would be positive! You'll have to determine whether the number is negative by yourself and either use the upper or the lower solution
• Jujumancer: Thank you. I''ll check it out with other values as well. I'll be using your method just for signed hex values. Cheers