Integer to two digits hex in Java

Question

I need to change a integer value into 2-digit hex value in Java.Is there any way for this. Thanks

My biggest number will be 63 and smallest will be 0. I want a leading zero for small values.

Solution 1

String.format("%02X", value);

If you use X instead of x as suggested by aristar, then you don't need to use .toUpperCase().

Solution 2

Integer.toHexString(42);

Javadoc: http://docs.oracle.com/javase/6/docs/api/java/lang/Integer.html#toHexString(int)

Note that this may give you more than 2 digits, however! (An Integer is 4 bytes, so you could potentially get back 8 characters.)

Here's a bit of a hack to get your padding, as long as you are absolutely sure that you're only dealing with single-byte values (255 or less):

Integer.toHexString(0x100 | 42).substring(1)

Many more (and better) solutions at Left padding integers (non-decimal format) with zeros in Java.

Solution 3

String.format("%02X", (0xFF & value));    

Solution 4

Use Integer.toHexString(). Dont forget to pad with a leading zero if you only end up with one digit. If your integer is greater than 255 you'll get more than 2 digits.

StringBuilder sb = new StringBuilder();
sb.append(Integer.toHexString(myInt));
if (sb.length() < 2) {
    sb.insert(0, '0'); // pad with leading zero if needed
}
String hex = sb.toString();

Solution 5

If you just need to print them try this:

for(int a = 0; a < 255; a++){
    if( a % 16 == 0){
        System.out.println();
    }
    System.out.printf("%02x ", a);
}

View more solutions

Comments

[Stealth Rabbi]

Can someone explain why this is doing a bit-wise and with 0xFF? This is why answers on SO shouldn't just be the code

[aristar]

OxFF & (byte)value just convert signed byte to unsigned. (int)-1 = 0xFFFFFFFF, (int)(-1 & 0xFf) = 0xFF

[just lerning]

Is the use of StringBuilder actually an improvement? pastebin.com/KyS06JMz

[David J.]

This is the best answer at present.

[JRSofty]

Agreed this one is much better than any of the others. It works perfectly. The only thing I would suggest is a little more description of the parameters passed to the method. I had to look up if I passed the value as an integer or as a hex string.

[Grodriguez]

Nice zero-padding hack :)

[Freek de Bruijn]

In this case, the bit-wise and with 0xFF is not necessary because of the "%02X" format.

[user823981]

You can use the same technique for larger values. If you want padding for up to 2-byte values you can do Integer.toHexString( 0x10000 | value).substring(1). For N hex digits you append N 0s after the "1". Of course, your hex value must have no more than N digits.

[plugwash]

The %02X specifier specifies a minimum of two digits. If you want exactly two digits (discarding higher bits) then you need the bitwise and.

[tryp]

Good to know, thanks for this additional information !

[mrek]

This unfortunately does not work for strings, you have to use a little calculation hack