hex : Java Glossary

hex

or hexadecimal, base 16 numbers, e.g. 08Cf, made of the digits 0..9 and a..f. This is the number system we would have used had we sixteen fingers instead of ten.

Even though in Java we specify decimal, hex, octal and other radix representations of int literals, inside the int, there is no radix. It is just string of 32 binary bits. When you display an int you are in some way picking a radix and converting it to String. Methods such an println do this for you, so it creates the illusion you are seeing the value of the int directly. It does not make sense to talk of the radix of an int, e.g. is this a hex or decimal int?, only the radix of some String representation of it.

Displaying With Hex Strings	Hex Literals
Hex with Lead Zeroes	Hex vs Decimal vs Binary
Hex String to int	Table of Hex digits
String to hex String	Hex Color Numbers
byte[] to String	Links
String to byte[]

Displaying With Hex Strings

You can display in hex using code like this:

Hex with Lead Zeroes

That won’t apply any lead zeroes. Here is how to get a lead zero for a fixed two character hex representation of a byte:

The method com.mindprod.common11.StringTools. toHexString is useful for debugging. It will give you an 8-char left-zero padded hex String representatation of an int.

// Available in download http://mindprod.com/products1.html#COMMON11
import com.mindprod.common11.StringTools;
...
// Prepare unsigned hex string padded out to 8 chars with lead zeroes.
final String display = StringTools.toHexString( someInt );

The method com.mindprod.common11.StringTools. toLzHexString will pad out to any desired size with lead zeros for you:

Hex String to int

You can convert a hex String to internal binary like this:

/* convert a hex String to int */
// Note, there is no lead 0x, case insensitive
String g = "af0c99";
int i = Integer.parseInt( g.trim(), 16 /* radix */ );

Since the computer uses binary internally, it makes no sense to talk about converting an int from hex to decimal or back, only a String.

String to hex String

Here is how you can convert a String to hex for display so you can tell precisely what each character is.

Use can also use Printwriter.printf( "%x", i ) to display a hex number.

byte[] to String

The following code looks complicated, but is considerably faster than built-in Java methods. It also handles a byte array, not just a single byte.

String to byte[]

And here is how to go the other way from a hex String back to a byte array:

Hex Literals

In Java you can use hex literals like this

// example of a hex 0x literal
int a = 0x8cf;

Hex vs Decimal vs Binary

The computer chip works internally in binary (base 2 numbers), with numbers made only of the digits 0 and 1, low voltage/high voltage. Binary numbers are somewhat bulky to write out, so they are usually written in base 16, hex. It is very easy to convert hex to binary and visa versa using the following table. For example, the hex number 8cf is 100011001111 in binary. Converting between decimal and hex is more difficult. You must do successive divisions and moduluses by 10 or 16.

Table of Hex digits

Decimal	Hex	Binary
0	0	0000
1	1	0001
2	2	0010
3	3	0011
4	4	0100
5	5	0101
6	6	0110
7	7	0111
8	8	1000
9	9	1001
10	a	1010
11	b	1011
12	c	1100
13	d	1101
14	e	1110
15	f	1111

You can handle arbitrarily large hex Strings with BigInteger.

Hex Color Numbers

010 Editor: a hex/binary editor with templates
BigInteger
binary
binary formats
BitSet
conversion
HexView: allows you to view files in hex
Learn To Count Applet to sharpen your intuition on how binary, hex, and octal work
literals
masking
mixed base
octal
PGP hex encoding as words
printf
radix
shift
SlickEdit: allows you to view files in hex
unsigned

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