Answers to Self-Study Questions for Sequences

BEFORE:  10   20   53   2
              ^
              |
            current


AFTER:   10   6    20   53   2
              ^
              |
            current

Part (b)

BEFORE:  10   20   53   2

AFTER:   6    10    20   53   2
         ^
         |
       current

private void expandArray() {
// allocate an array of twice the size of the "items" array
// copy all values from "items" to the new array
// assign "items" to refer to the new array

  Object[] tmp = new Object[items.length*2];
  System.arraycopy(items, 0, tmp, 0, items.length);
  items = tmp;
}

Question 2: The moveItemsRight method can be implemented using a loop to move the items, like this:

private void moveItemsRight(int start) {
// move all of the items in the sequence, starting with the item with
// index "start", one place to the right (i.e., move items[start] to
// items[start+1], move items[start+1] to items[start+2], etc

  for (int k=numItems-1; k>=start; k--) {
      items[k+1] = items[k];
  }
}

It can also be implemented using System.arraycopy, like this:

private void moveItemsRight(int start) {
// move all of the items in the sequence, starting with the item with
// index "start", one place to the right (i.e., move items[start] to
// items[start+1], move items[start+1] to items[start+2], etc

  System.arraycopy(items, start, items, start+1, numItems-start);
}