Problem 2

Start with the file LList2.java and add the following methods:

4.Add the method

int getLastIndex(T item)

that returns the index of the last entry which is equal to item. If item is not found, it returns -1. (15 points)

5.Add the method

int removeEvery(T item) that removes all occurrences of item and returns the number of removed items. (15 points)

6.Add the method

boolean equals(Object other) method that returns true when the contents of 2 LList2 objects are the same (the two objects in this case are the current object and other). Note that 2 LList2 objects are the same if they have the same number of items and each item in one object exists in the same location in the other object (15 points)

7.Provide a second implementation of the method

boolean contains2(T anEntry)

that calls a private recursive method

private boolean contains(T anEntry, Node startNode)

that returns whether the list that starts at startNode contains the entry anEntry. (10 points)

LList2.java

/** A class that implements the ADT list by using a chain of nodes. The chain has both a head reference and a tail reference. @author Frank M. Carrano @version 3.0 */ public class LList2 implements ListInterface { private Node firstNode; // head reference to first node private Node lastNode; // tail reference to last node private int numberOfEntries;

public LList2() { clear(); } // end default constructor

public final void clear() // NOTICE clear is not final in interface and that is OK { firstNode = null; lastNode = null; numberOfEntries = 0; } // end clear public void add(T newEntry) // OutOfMemoryError possible { Node newNode = new Node(newEntry); // create new node

if (isEmpty()) firstNode = newNode; else lastNode.setNextNode(newNode); lastNode = newNode; numberOfEntries++; } // end add

public boolean add(int newPosition, T newEntry) // OutOfMemoryError possible { boolean isSuccessful = true;

if ((newPosition >= 1) && (newPosition <= numberOfEntries + 1)) { Node newNode = new Node(newEntry);

if (isEmpty()) { firstNode = newNode; lastNode = newNode; } else if (newPosition == 1) { newNode.setNextNode(firstNode); firstNode = newNode; } else if (newPosition == numberOfEntries + 1) { lastNode.setNextNode(newNode); lastNode = newNode; } else { Node nodeBefore = getNodeAt(newPosition - 1); Node nodeAfter = nodeBefore.getNextNode(); newNode.setNextNode(nodeAfter); nodeBefore.setNextNode(newNode); } // end if numberOfEntries++; } else isSuccessful = false; return isSuccessful; } // end add

public T remove(int givenPosition) { T result = null; // return value

if ((givenPosition >= 1) && (givenPosition <= numberOfEntries)) { assert !isEmpty(); if (givenPosition == 1) // case 1: remove first entry { result = firstNode.getData(); // save entry to be removed firstNode = firstNode.getNextNode(); if (numberOfEntries == 1) lastNode = null; // solitary entry was removed } else // case 2: givenPosition > 1 { Node nodeBefore = getNodeAt(givenPosition - 1); Node nodeToRemove = nodeBefore.getNextNode(); Node nodeAfter = nodeToRemove.getNextNode(); nodeBefore.setNextNode(nodeAfter); // disconnect the node to be removed result = nodeToRemove.getData(); // save entry to be removed

if (givenPosition == numberOfEntries) lastNode = nodeBefore; // last node was removed } // end if

numberOfEntries--; } // end if

return result; // return removed entry, or // null if operation fails } // end remove

public boolean replace(int givenPosition, T newEntry) { boolean isSuccessful = true;

if ((givenPosition >= 1) && (givenPosition <= numberOfEntries)) { assert !isEmpty();

Node desiredNode = getNodeAt(givenPosition); desiredNode.setData(newEntry); } else isSuccessful = false; return isSuccessful; } // end replace

public T getEntry(int givenPosition) { T result = null; // result to return if ((givenPosition >= 1) && (givenPosition <= numberOfEntries)) { assert !isEmpty(); result = getNodeAt(givenPosition).getData(); } // end if return result; } // end getEntry

public boolean contains(T anEntry) { boolean found = false; Node currentNode = firstNode; while (!found && (currentNode != null)) { if (anEntry.equals(currentNode.getData())) found = true; else currentNode = currentNode.getNextNode(); } // end while return found; } // end contains

public int getLength() { return numberOfEntries; } // end getLength

public boolean isEmpty() { boolean result; if (numberOfEntries == 0) // or getLength() == 0 { assert firstNode == null; result = true; } else { assert firstNode != null; result = false; } // end if return result; } // end isEmpty public T[] toArray() { // the cast is safe because the new array contains null entries @SuppressWarnings("unchecked") T[] result = (T[])new Object[numberOfEntries]; // warning: [unchecked] unchecked cast

int index = 0; Node currentNode = firstNode; while ((index < numberOfEntries) && (currentNode != null)) { result[index] = currentNode.getData(); currentNode = currentNode.getNextNode(); index++; } // end while return result; } // end toArray

// Returns a reference to the node at a given position. // Precondition: List is not empty; 1 <= givenPosition <= numberOfEntries. private Node getNodeAt(int givenPosition) { assert (firstNode != null) && (1 <= givenPosition) && (givenPosition <= numberOfEntries); Node currentNode = firstNode; if (givenPosition == numberOfEntries) currentNode = lastNode; else if (givenPosition > 1) // traverse the chain to locate the desired node { for (int counter = 1; counter < givenPosition; counter++) currentNode = currentNode.getNextNode(); } // end if assert currentNode != null; return currentNode; } // end getNodeAt

// Lab 3 // Problem 1 int getIndex(T item) { return 0; } // Problem 2 int removeEvery(T item) { return 0; } // Problem 3 boolean equals(Object other) { return false; } //Problem 4 boolean contains2(T anEntry) { return false; } private boolean contains(T anEntry, Node startNode) { return false; } private class Node { private T data; // data portion private Node next; // next to next node

private Node(T dataPortion)// PRIVATE or PUBLIC is OK { data = dataPortion; next = null; } // end constructor

private Node(T dataPortion, Node nextNode)// PRIVATE or PUBLIC is OK { data = dataPortion; next = nextNode; } // end constructor

private T getData() { return data; } // end getData private void setData(T newData) { data = newData; } // end setData private Node getNextNode() { return next; } // end getNextNode private void setNextNode(Node nextNode) { next = nextNode; } // end setNextNode } // end Node } // end LList2

ListInterface

/** An interface for the ADT list. Entries in the list have positions that begin with 1.

@author Frank M. Carrano @version 3.0 */ public interface ListInterface { /** Adds a new entry to the end of this list. Entries currently in the list are unaffected. The lists size is increased by 1. @param newEntry the object to be added as a new entry */ public void add(T newEntry); /** Adds a new entry at a specified position within this list. Entries originally at and above the specified position are at the next higher position within the list. The lists size is increased by 1. @param newPosition an integer that specifies the desired position of the new entry @param newEntry the object to be added as a new entry @return true if the addition is successful, or false if newPosition < 1, or newPosition > getLength() + 1 */ public boolean add(int newPosition, T newEntry); /** Removes the entry at a given position from this list. Entries originally at positions higher than the given position are at the next lower position within the list, and the lists size is decreased by 1. @param givenPosition an integer that indicates the position of the entry to be removed @return a reference to the removed entry or null, if either the list was empty, givenPosition < 1, or givenPosition > getLength() */ public T remove(int givenPosition); /** Removes all entries from this list. */ public void clear(); /** Replaces the entry at a given position in this list. @param givenPosition an integer that indicates the position of the entry to be replaced @param newEntry the object that will replace the entry at the position givenPosition @return true if the replacement occurs, or false if either the list is empty, givenPosition < 1, or givenPosition > getLength() */ public boolean replace(int givenPosition, T newEntry); /** Retrieves the entry at a given position in this list. @param givenPosition an integer that indicates the position of the desired entry @return a reference to the indicated entry or null, if either the list is empty, givenPosition < 1, or givenPosition > getLength() */ public T getEntry(int givenPosition); /** Sees whether this list contains a given entry. @param anEntry the object that is the desired entry @return true if the list contains anEntry, or false if not */ public boolean contains(T anEntry); /** Gets the length of this list. @return the integer number of entries currently in the list */ public int getLength(); /** Sees whether this list is empty. @return true if the list is empty, or false if not */ public boolean isEmpty(); /** Retrieves all entries that are in this list in the order in which they occur in the list. */ public T[] toArray(); } // end ListInterface

ListClient

public class ListClient { public static void main(String[] args) { testList(); } // end main

public static void testList() { ListInterface runnerList = new AList(); // runnerList has only methods in ListInterface

runnerList.add("16"); // winner runnerList.add(" 4"); // second place runnerList.add("33"); // third place runnerList.add("27"); // fourth place displayList(runnerList); } // end testList public static void displayList(ListInterface list) { int numberOfEntries = list.getLength(); System.out.println("The list contains " + numberOfEntries + " entries, as follows:"); for (int position = 1; position <= numberOfEntries; position++) System.out.println(list.getEntry(position) + " is entry " + position); System.out.println(); } // end displayList } // end ListClient