Convert hex string to int

Question

I am trying to convert a string that is 8 characters long of hex code into an integer so that I can do int comparison instead of string comparisons over a lot of different values   I know this is fairly trivial in C   but I need to do it in Java   The test case I need to satisfy is essentially to Convert  AA0F245C  to int and then back to that string so that I know it is converting right   I have tried the following   int decode   Integer decode  0xAA0F245C        NumberFormatException int decode2   Integer decode  AA0F245C      NumberFormatException int parseInt   Integer parseInt  AA0F245C   16     NumberFormatException int valueOf   Integer valueOf  AA0F245C   16     NumberFormatException   I have also tried doing it two characters at a time and multiplying the results  which the conversion works but the number is not right   int id   0  for  int h   0  h  lt  hex length    h  h 2        String sub   hex subSequence h  h 2  toString     if  id    0      id   Integer valueOf sub  16   else     id    Integer valueOf sub  16                     ID   8445600 which   80DEA0 if I convert it back     I can not use third party libraries just so you know  so this has to be done in Java standard libraries    Thank you for your help in advance

User · Answer

The maximum value that a Java Integer can handle is 2147483657  or 2 31-1   The hexadecimal number AA0F245C is 2853119068 as a decimal number  and is far too large  so you need to use   Long parseLong  AA0F245C   16     to make it work

User · Answer

It s simply too big for an int  which is 4 bytes and signed    Use   Long parseLong  AA0F245C   16

User · Answer

For those of you who need to convert hexadecimal representation of a signed byte from two-character String into byte  which in Java is always signed   there is an example  Parsing a hexadecimal string never gives negative number  which is faulty  because 0xFF is -1 from some point of view  two s complement coding   The principle is to parse the incoming String as int  which is larger than byte  and then wrap around negative numbers  I m showing only bytes  so that example is short enough   String inputTwoCharHex  FE     whatever your microcontroller data is  int i Integer parseInt inputTwoCharHex 16     negative numbers is i now look like 128   255     shortly i gt  128 if  i gt  Integer parseInt  80  16           need to wrap-around negative numbers       we know that FF is 255 which is -1       and FE is 254 which is -2 and so on     i -1-Integer parseInt  FF  16  i        shortly i -256 i    byte b  byte i    b is now surely between -128 and  127   This can be edited to process longer numbers  Just add more FF s or 00 s respectively  For parsing 8 hex-character signed integers  you need to use Long parseLong  because FFFF-FFFF  which is integer -1  wouldn t fit into Integer when represented as a positive number  gives 4294967295   So you need Long to store it  After conversion to negative number and casting back to Integer  it will fit  There is no 8 character hex string  that wouldn t fit integer in the end

User · Answer

An additional option to the ones suggested  is to use the BigInteger class  Since hex values are often large numbers  such as sha256 or sha512 values  they will easily overflow an int and a long  While converting to a byte array is an option as other answers show  BigInterger  the often forgotten class in java  is an option as well   String sha256    65f4b384672c2776116d8d6533c69d4b19d140ddec5c191ea4d2cfad7d025ca2   BigInteger value   new BigInteger sha256  16   System out println  value       value      46115947372890196580627454674591875001875183744738980595815219240926424751266

User · Answer

you may use like that   System out println Integer decode  0x4d2          output 1234   and vice versa  System out println Integer toHexString 1234       output is 4d2

User · Answer

Try with this   long abc convertString2Hex  1A2A3B     private  long  convertString2Hex String numberHexString        char   ChaArray   numberHexString toCharArray        long HexSum 0      long cChar  0       for int i 0 i lt numberHexString length   i                   if   ChaArray i  gt   0    amp  amp   ChaArray i  lt   9                 cChar   ChaArray i  -  0           else             cChar   ChaArray i - A  10          HexSum   16   HexSum   cChar            return  HexSum

User · Answer

Method for Smaller Number Range  Integer parseInt  abc  16      Method for Bigger Number Range  Long parseLong  abc  16      Method for Biggest Number Range  new BigInteger  abc  16

User · Answer

This is the right answer    myPassedColor     ffff8c85  int colorInt   Color parseColor myPassedColor

User · Answer

you can easily do it with parseInt with format parameter   Integer parseInt  -FF   16       returns -255   javadoc Integer

[java] Convert hex string to int

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