update,

it114105/itp4510/Lab03/Lab3.3/LinkedList.java

@@ -0,0 +1,88 @@
+public class LinkedList {
+	private ListNode head;
+	private ListNode tail;
+	private int count;
+
+	public LinkedList() {
+		head = null;
+		tail = null;
+		count = 0;
+	}
+
+	public boolean isEmpty() {
+		return (head==null);
+	}
+
+	public int getCount() {
+		return count;
+	}
+
+	public void addToHead(Object item) {
+		count++;
+		if (isEmpty()) {
+			head = tail = new ListNode(item);
+		} else {
+			head = new ListNode(item, head);
+		}
+	}
+
+	public void addToTail(Object item) {
+		count++;
+		if (isEmpty()) {
+			head = tail = new ListNode(item);
+		} else {
+			tail.next = new ListNode(item);
+			tail =  tail.next;
+		}
+	}
+
+	public Object removeFromHead() throws EmptyListException {
+		if (isEmpty()) {
+			throw new EmptyListException();
+		} 
+		Object item = head.data;
+		if (head == tail) // there's only one single node
+			head = tail = null;
+		else
+			head = head.next;
+		count--;
+		return item;
+	}
+
+	public Object removeFromTail() throws EmptyListException {
+		if (isEmpty()) {
+			throw new EmptyListException();
+		} 
+		count--;
+		Object item = tail.data;
+		if (head == tail) {   // there is only one node
+			head = tail = null;
+			return item;
+		}
+		// search for the second last node 
+		ListNode current = head;
+		while (current.next != tail)
+			current = current.next;
+		// set second last node as new tail
+		tail = current;
+		tail.next = null;
+		return item;
+	}
+
+	public String toString() {
+		String s = "[ ";
+
+		// traverse the list from head towards tail
+		ListNode current = head;
+		while (current != null) {
+			s += current.data + " ";
+			current = current.next;
+		}
+		return s + "]";
+	}
+}
+
+
+
+
+