Question

I’m aware that a common performance refactoring is to replace simple for‘s by System.arraycopy.

I want to ask about:

1. When exactly does system.arraycopy begin to make sense (considering it’s a native method call). Does copying small things say, < 32 have any advantage?

2. Is it my impression, or is it not simply possible to copy (efficiently) a cycle like this with arraycopy:

      for (int j = 0; j < 2; ++j) {
          vpr[m][s + j][i] = vr[j];
      }
   

Answer 1

System.arrayCopy is likely the fastest way to copy an array, but it does not make deep copies.

It also cannot do the more complex example in your second question.