public void addFirst(Item item) {
if (item == null) {
throw new java.lang.NullPointerException("Cannot add a null item!");
}
Node oldFirst = first;
first = new Node();
first.item = item;
first.pre = null;
if (last == null) { // condition must be this. Cannot be
// "if(isEmpty())"!!! because it can't be empty now
last = first;
} else {
first.next = oldFirst;
oldFirst.pre = first;
}
N++;
}
private Node add(Node x, String key, int d) {
if (x == null) x = new Node();
if (d == key.length()) {
if (!x.isString) N++;
x.isString = true;
} else {
char c = key.charAt(d);
x.next[c - 65] = add(x.next[c - 65], key, d + 1);
}
return x;
}
public Item removeLast() {
if (isEmpty()) {
throw new java.util.NoSuchElementException("Cannot remove an item from an empty deque!");
}
Item rm = last.item;
last = last.pre;
last.next = null;
if (isEmpty()) {
first = null;
}
N--;
return rm;
}
public void addLast(Item item) {
if (item == null) {
throw new java.lang.NullPointerException("Cannot add a null item!");
}
Node oldLast = last;
last = new Node();
last.item = item;
last.next = null;
if (isEmpty()) {
last.pre = null;
first = last;
} else {
oldLast.next = last;
last.pre = oldLast;
}
N++;
}