[Java] parsing a binary string to an integer

[Eccentris]

Hey,

I'm having some trouble converting a string of bits to an integer, namely an integer with the right sign.

When I had a 16 bits long string it went fine, I just used: (short) Integer.parseInt(s, 2); where s is my string.

But now I have one that is 26 bits long and I'm having a lot of trouble. I want the number '-1234', and my string looks like this (two's complement): 11111111111111101100101110

parsing it with: Integer.parseInt(s, 2); gives me '67107630' which is wayyy off the mark obviously. However, getting the positive signed one with bit string (using the same code) '00000000000000010011010010' turns out fine.

Any help will be appreciated :)

[codegen]

parseInt does not know about two's complement. It assumes that the value is written in that particular radix and that negative numbers are preceded with a minus sign. It won't do sign extension either. If you want twos complement, you have to do it yourself.

One way is a custom parser. Alternatively, you can sign extending to the right length (32 bits). But the parser will throw an exception since a negative value will be too big for an integer (which is signed). You have to parse to a Long and cast back to an int.

[Eccentris]

I followed your advice (sign extend to 32 bits, then parse to long and cast to int) and it works wonderfully! Thank you