How to get a sub array of array in Java, without copying data?

Question

I have some library of classes, working with my data, which is being read into buffer. Is it possible somehow to avoid copying arrays again and again, passing parts of data deeper and deeper into processing methods? Well, it sounds strange, but in my particular case, there's a special writer, which divides data into blocks and writes them individually into different locations, so it just performs System.arraycopy, gets what it needs and calls underlying writer, with that new sub array. And this happens many times. What is the best approach to refactor such code?

Answer 1

Have a look on Arrays.copyOfRange(***) methods.

Answer 2

You could take the same approach as the String class takes; create a class for immutable objects which are constructed from an array, a start offset and an end offset which offers access to the sub-array. The user of such an object does not have to know the distinction between the whole array or a sub-array. The constructor does not have to copy the array, just store the array reference and its boundaries.

Answer 3

Many classes in Java accept a subset of an arrays as parameter. E.g. Writer.write(char cbuf[], int off, int len). Maybe this already suffices for your usecase.

Answer 4

Arrays.asList(array).subList(x, y).

It doesn't give you an array, but a List, which is far more flexible.