Bit patterns in Java

Question

How do I create a bit pattern (bit string, bit stream?) in Java?
What I'd like to do is to contract data and use a bit pattern instead of the Java built-in standard classes. With what Java tools/classes can I achieve this?
Example: Storing personal data for a high school student:
Bit 1 (nationality): American=0, Foreigner=1
Bit 2 (sex): male=0, female=1
Bit 3-4 (grade/class): freshman=00, sophomore=01, junior=10, senior=11
And so on...
The bit pattern is supposed to be able to hold a lot of information, at least a 100 bits or so.
Thanks!
/peso

Answer 1

peso wrote:
Thanks for your reply JoachimSauer. You're right in what you're saying that space is cheap and all, but in this case it's essential for my application that I store the information in as few bits as possible.Why is that, I wonder? Out of curiosity. Are you storing/transfering so many records or is the space/bandwidth so limited?
And I'm also interested in learning the best way to create and build a bit pattern with the information I have.
Say I have about a hundred different strings containing different information:
String nationality = "American";
String sex = "Male";
String grade = "Sophomore";
String age = "17";
Etc...
I could store this as for example "American;Male;Sophomore;17".The first step would be to get rid of any Strings and transfer that to some better-fitting datatypes. For example create an enum for nationality (even if it only got the values AMERICAN and FOREIGN, I wouldn't call that nationality, btw).
Then an enum for the sex and grade. And use an int to store the age.
Because using Strings for things which aren't arbitary (or at least somewhat freeform) character strings is ... wrong.
But what I'd like to do is to encode this information in a bit pattern like for example "0 0 01 10001" and then converting the bit pattern into a string of ASCII characters by taking lets say 5 bits at a time. Say the beginning of my bit pattern would look like "01011 00101 11001 11110 01000". That would produce the following string with ASCII characters (if I add 33 to the value in order to get a value which represents a writable ASCII character) ",&:?)".I'd use the Base64 encoding, if an ASCII-representation was absolutely needed. But if you really need to use as little space as possible, then you should keep a binary format.
So the question is, what's the best way to build my bit pattern? Say I need 124 bits for all my information. Do I create a byte array of size 16 and manipulate each byte by shifting and masking? Or is there another way to do it?Use a BitSet.