Java hex byte array converting to integer without converting to String first

Question

I'm trying to convert byte array which holds hex values.

byte[] bytes = {48, 48, 48, 48, 48, 51, 51, 99}

for example : 48, 48, 48, 48, 48, 51, 51, 99 is 0000033c and converted to int is 828. The only way to convert is converting it to String and then parse integer from String.

 public static int ConvertValueFromBytes(byte[] bytes)
    {
        String b = new String(bytes);
        return Converter.ConvertHexToInt(b);
    }

The main problem here is performance, calling it many times can cause performance issues. When trying parse int value from byte array I get massive numbers, thats why I'm parsing from String, to get the correct value. Is there a better way or solution to this ?

Something doesn't add up in your logic. Why are you storing what is essentially a string representation of a hexadecimal value in a byte array? Your byte array should probably look like this: byte[] bytes = {0, 0, 3, 60}, or even just {3, 60}. — Robby Cornelissen
– Robby Cornelissen, Commented Sep 25, 2018 at 7:57
Possible duplicate of: stackoverflow.com/questions/9655181/… — Tim Biegeleisen
– Tim Biegeleisen, Commented Sep 25, 2018 at 7:57
I have a large one string hex value which contains up to 2000+ characters. What I'm doing is splitting them to smaller parts to get the int value. — MINIKAS
– MINIKAS, Commented Sep 25, 2018 at 8:00
There's no need to base yourself on the character values of your hex string. Every two characters represent one byte, so you should parse them as such. — Robby Cornelissen
– Robby Cornelissen, Commented Sep 25, 2018 at 8:02

Andy Turner · Accepted Answer · 2018-09-25 08:00:22Z

1

Whilst it's very unclear why you would represent the data in this way, it's easy to transform without using a string:

int v = 0;
for (byte b : bytes) {
  v = 16 * v + Character.getNumericValue(b);
}

Ideone demo

answered Sep 25, 2018 at 8:00

Andy Turner

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2 Comments

MINIKAS Over a year ago

This kind of works and parsing negative values as well. Can you explain me please how this for loop works ?

Andy Turner Over a year ago

0x123 is (((1) * 16 + 2) * 16) + 3.

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