Java – converts long to “byte array ed” text without heap allocation

I want to convert the (positive) original long into byte []

For example, a simple method is: 123 = > "123" = > [49,50,51]

However, converting long to string heap - assigns a string, which I try to avoid for my GC free library I'd rather render it directly on a preallocated byte array

Therefore, my problem is how to convert directly from long to byte [] representation. If I use the string constructor call (for the above example), I give "123" For clarity, I'm not going to encode long as a binary byte [], but as text

thank you! ñ

Solution

This simple procedure:

long l = 123;
int size = (int)(Math.log10(l)+1);
byte[] array = new byte[size];
for (int i = 0; i < size; i++) {
    long temp = (long) Math.pow(10,size - i - 1);
    array[i] = (byte) ((l / temp) + 48);
    l = l % temp;
}
System.out.println(Arrays.toString(array)); // [49,51]

I have tested the current time in milliseconds and worked as expected:

long l = System.currentTimeMillis();
...
System.out.println(Arrays.toString(array));

Output:

1406485727149
[49,52,48,54,56,53,55,49,57]