Question

I have this method which add spaces to the start of byte array. problem is that I am not sure if this is the most faster implementation of this task. Is there some options to add space faster ? if yes please add here some sollution

public static byte[] doplnMezery(byte[] item, int numberOfSpaces) {
    int lenghtOfItem = item.length;

    for (int i = lenghtOfItem; i < numberOfSpaces; i++) {
        item = ArrayUtils.add(item, 0, (byte) 32);
    }
    return item;
}

Answer 1

That seems inefficient since the add method can’t run faster than linear time. What you get here is a quadratic algorithm.

Something like this should be faster (linear time complexity).

public static byte[] doplnMezery(byte[] item, int numberOfSpaces) {
    byte[] result = new byte[item.length + numberOfSpaces];
    Arrays.fill(result, 0, numberOfSpaces, (byte) 32);
    System.arraycopy(item, 0, result, numberOfSpaces, item.length);        
    return result;
}