public class SinglyLinkedList implements Cloneable, Iterable { //---------------- nested Node class ---------------- /** * Node of a singly linked list, which stores a reference to its * element and to the subsequent node in the list (or null if this * is the last node). */ private static class Node {

/** The element stored at this node */ private E element; // reference to the element stored at this node

/** A reference to the subsequent node in the list */ private Node next; // reference to the subsequent node in the list

/** * Creates a node with the given element and next node. * * @param e the element to be stored * @param n reference to a node that should follow the new node */ public Node(E e, Node n) { element = e; next = n; }

// Accessor methods /** * Returns the element stored at the node. * @return the element stored at the node */ public E getElement() { return element; }

/** * Returns the node that follows this one (or null if no such node). * @return the following node */ public Node getNext() { return next; }

// Modifier methods /** * Sets the node's next reference to point to Node n. * @param n the node that should follow this one */ public void setNext(Node n) { next = n; } } //----------- end of nested Node class -----------

// instance variables of the SinglyLinkedList /** The head node of the list */ private Node head = null; // head node of the list (or null if empty)

/** The last node of the list */ private Node tail = null; // last node of the list (or null if empty)

/** Number of nodes in the list */ private int size = 0; // number of nodes in the list

/** Constructs an initially empty list. */ public SinglyLinkedList() { } // constructs an initially empty list

// access methods /** * Returns the number of elements in the linked list. * @return number of elements in the linked list */ public int size() { return size; }

/** * Tests whether the linked list is empty. * @return true if the linked list is empty, false otherwise */ public boolean isEmpty() { return size == 0; }

/** * Returns (but does not remove) the first element of the list * @return element at the front of the list (or null if empty) */ public E first() { // returns (but does not remove) the first element if (isEmpty()) return null; return head.getElement(); }

/** * Returns (but does not remove) the last element of the list. * @return element at the end of the list (or null if empty) */ public E last() { // returns (but does not remove) the last element if (isEmpty()) return null; return tail.getElement(); } /** * Returns (but does not remove) the penultimate node of the list. * @return node before the end of the list - exception if size (e, head); // create and link a new node if (size == 0) tail = head; // special case: new node becomes tail also size++; }

/** * Adds an element to the end of the list. * @param e the new element to add */ public void addLast(E e) { // adds element e to the end of the list Node newest = new Node(e, null); // node will eventually be the tail if (isEmpty()) head = newest; // special case: previously empty list else tail.setNext(newest); // new node after existing tail tail = newest; // new node becomes the tail size++; } /** * Adds an element to be the second of the list. * @param e the new element to add */ public void addSecond(E e) { //***** Complete this method *****// } /** * Adds an element at the ith position in the list. * @param e the new element to add. */ public void add(E e, int i) { //***** Complete this method *****// }

/** * Removes and returns the first element of the list. * @return the removed element (or null if empty) */ public E removeFirst() { // removes and returns the first element if (isEmpty()) return null; // nothing to remove E answer = head.getElement(); head = head.getNext(); // will become null if list had only one node size--; if (size == 0) tail = null; // special case as list is now empty return answer; } /** * Removes and returns the ith element of the list. * @return the removed element exception i not in proper range */ public E remove(int i) { //***** Complete this method *****// return null; } /** * Reverses the order of the nodes in the list. * */ public void reverse() { //***** Complete this method *****// }

@SuppressWarnings({"unchecked"}) public boolean equals(Object o) { if (o == null) return false; if (getClass() != o.getClass()) return false; SinglyLinkedList other = (SinglyLinkedList) o; // use nonparameterized type if (size != other.size) return false; Node walkA = head; // traverse the primary list Node walkB = other.head; // traverse the secondary list while (walkA != null) { if (!walkA.getElement().equals(walkB.getElement())) return false; //mismatch walkA = walkA.getNext(); walkB = walkB.getNext(); } return true; // if we reach this, everything matched successfully }

@SuppressWarnings({"unchecked"}) public SinglyLinkedList clone() throws CloneNotSupportedException { // always use inherited Object.clone() to create the initial copy SinglyLinkedList other = (SinglyLinkedList) super.clone(); // safe cast if (size > 0) { // we need independent chain of nodes other.head = new Node(head.getElement(), null); Node walk = head.getNext(); // walk through remainder of original list Node otherTail = other.head; // remember most recently created node while (walk != null) { // make a new node storing same element Node newest = new Node(walk.getElement(), null); otherTail.setNext(newest); // link previous node to this one otherTail = newest; walk = walk.getNext(); } } return other; }

public int hashCode() { int h = 0; for (Node walk=head; walk != null; walk = walk.getNext()) { h ^= walk.getElement().hashCode(); // bitwise exclusive-or with element's code h = (h >> 27); // 5-bit cyclic shift of composite code } return h; }

/** * Produces a string representation of the contents of the list. * This exists for debugging purposes only. */ public String toString() { StringBuilder sb = new StringBuilder("("); Node walk = head; while (walk != null) { sb.append(walk.getElement()); if (walk != tail) sb.append(", "); walk = walk.getNext(); } sb.append(")"); return sb.toString(); } /** * Implements java.lang.Iterable */ public java.util.Iterator iterator() { return new ForwardIterator(); } private class ForwardIterator implements java.util.Iterator { //***** Define appropriate instance variables here *****//

public boolean hasNext() { //***** Complete this method *****// return false; }

// Note: this method has undefined behavior if hasNext() return false public E next() { //***** Complete this method *****// return null; } } }

Your Tasks Complete the following tasks. When you are finished you should be able to run the provided tester and get correct output for all tasks. a. Complete the penultimateNode () method. (See exercise R-3.6). b. Complete a reverse () method for the SinglyLinkedList class. Empty method has been provided for you. Add a addSecond (E e) method - If list is empty, throw exception. Parameter e will be the second element in the list after this operation has completed. This method should return void. d. Complete an add (E e, int i) method to the SinglyLinkedList class. What is the run time of this method? Throw an exception if is exception in the scoreboard example in class). ( must be >= 0 and