public class LinkedList {

private class Node {

Object data;

Node next;

public Node(Object data, Node next) {

this.data = data;

this.next = next;

}

}

private Node front;

/**

* Add a new item to the front of this list.

*/

public void addFront(Object item) {

front = new Node(item, front);

}

/**

* Return the item at the front of this list and remove it from this list.

*/

public Object removeFront() {

if (null == front) {

throw new RuntimeException("Can't removeFront() on empty list.");

}

Object answer = front.data;

front = front.next;

return answer;

}

/**

* The number of items in this list.

*/

public int length() {

int len = 0;

Node node = front;

while (node != null) {

len++;

node = node.next;

}

return len;

}

/**

* @return true if this list has no elements, false otherwise.

*/

public boolean isEmpty() {

return front == null;

}

public String toString() {

StringBuffer sb = new StringBuffer("[");

for (Node node = front; node != null; node = node.next) {

sb.append(node.data + " ");

}

return sb.toString() + "]";

}

public void insertAfter(Object existingItem, Object newItem) {

Node curNode = front;

while (!curNode.data.equals(existingItem) &&

(curNode.next != null)) {

curNode = curNode.next;

}

Node newNode = new Node(newItem, curNode.next);

curNode.next = newNode;

}

public static void main(String[] args) {

LinkedList lst = new LinkedList();

lst.addFront("Thorny");

lst.addFront("Farva");

lst.addFront("Mac");

lst.addFront("Rabbit");

lst.addFront("Foster");

System.out.println(lst);

System.out.println("How many? " + lst.length());

lst.insertAfter("Rabbit", "Ursula");

System.out.println(lst);

System.out.println("How many? " + lst.length());

lst.insertAfter("Spread it on!", "Chimpo");

System.out.println(lst);

System.out.println("How many? " + lst.length());

}

}