The document outlines the implementation of a generic ListNode class and two data structures: Queue and Stack, both using linked list techniques. The Queue class includes methods for enqueueing, dequeueing, and peeking at values, while the Stack class provides methods for pushing, popping, and peeking values. Additionally, it details a LinkedList class with methods for adding, removing, and accessing nodes, as well as an iterator for traversing the linked list.

1. Create a new java class called ListNode. Implement ListNode as a generic version of IntNode.
public class ListNode { }
Create a generic class called Queue, which is a linked list implementation of a queue data type.
Queue must have the following methods:
• public void enqueue(T value){} This method should add a new node to the back of the queue.
• public T dequeue(){} This method should remove a node from the front of the queue and return
its value
• public T peek(){} This method should return the value of the front node without removing it
from the queue
Create a new generic class called Stack, which is a linked list implementation of a stack data
type. Stack must have the following methods:
• public void push(T value){} This method should add a new node to the top of the stack.
• public T pop(){} This method should remove a node from the top of the stack and return its
integer value
• public T peek(){} This method should return the integer value of the top node without
removing it from the stack
Solution
import java.util.Iterator;
public class LinkedList extends AbstractList {
private ListNode front; // refers to first node in list (null if empty)
public LinkedList() {
front = null; // null front means empty
}
public void add(int index, E value) {
if (index == 0) {
// insert at the front
front = new ListNode(value, front);
} else {
ListNode current = goTo(index - 1);
ListNode newNode = new ListNode(value, current.next);

2. current.next = newNode;
}
}
public E get(int index) {
ListNode current = goTo(index);
return current.data;
}
public int indexOf(E value) {
int index = 0;
ListNode current = front;
while (current != null) {
if (current.data == value) {
return index;
}
index++;
current = current.next;
}
return -1;
}
public Iterator iterator() {
return new LinkedListIterator();
}
public void remove(int index) {
if (index == 0) {
// removing from the front
front = front.next;
} else {
ListNode current = goTo(index - 1);

3. current.next = current.next.next; // deletes the node
}
}
public void set(int index, E value) {
ListNode current = goTo(index);
current.data = value;
}
public int size() {
int count = 0;
ListNode current = front;
while (current != null) {
current = current.next;
count++;
}
return count;
}
public String toString() {
if (front == null) {
return "[]";
} else {
String result = "[" + front.data;
ListNode current = front.next;
while (current != null) {
result += ", " + current.data;
current = current.next;
}
result += "]";
return result;
}
}

4. private ListNode goTo(int index) {
ListNode current = front;
for (int i = 0; i < index; i++) {
current = current.next;
}
return current;
}
public class ListNode {
public E data;
public ListNode next;
public ListNode(E data) {
this.data = data;
this.next = null;
}
public ListNode(E data, ListNode next) {
this.data = data;
this.next = next;
}
}
private class LinkedListIterator implements Iterator {
private ListNode current; // current position in list
public LinkedListIterator() {
current = front;
}
public boolean hasNext() {
return current != null;
}
public E next() {
E result = current.data;
current = current.next;
return result;

5. }
public void remove() {
throw new UnsupportedOperationException();
}
}
}