The java.util.Arrays class has the copyOf method, which can be used to quickly create a copy of a given array. The length parameter of this method allows easily extending or truncating the returned copy. For example:

    String[] arr = { "B", "C", "D" };
    String[] copy1 = Arrays.copyOf(arr, arr.length + 1);
    copy1[copy1.length - 1] = "E"; // extend array by one element
    String[] copy2 = Arrays.copyOf(arr, arr.length - 1); // drop last element

However, this only allows a client to extend or truncate at the _end_ of the array. So, e.g. if a client wants to insert extra elements at the start of the array, they need to fall back to using System.arraycopy:

    String[] arr = { "B", "C", "D" };
    String[] copy = new String[arr.length + 1];
    copy[0] = "A";
    System.arraycopy(arr, 0, copy, 1, arr.length);

It would be nice if there was a util method in Arrays that allowed extending or truncating at the _start_ of an array as well. e.g.:

    String[] arr = { "B", "C", "D" };
    String[] copy1 = Arrays.copyOfTrailing(arr, arr.length + 1);
    copy1[0] = "A"; // extend
    String[] copy2 = Arrays.copyOfTrailing(arr, arr.length - 1); // truncate

This is a bit shorter, and avoids users having to manually use System.arraycopy, which is a quite low-level API.