In the Assignment #10, you are given three files Assignment10.java, LinkedList.j
ID: 3740252 • Letter: I
Question
In the Assignment #10, you are given three files Assignment10.java, LinkedList.java, and ListIterator.java. You will need to add additional methods in the LinkedList class in the LinkedList.java file. The LinkedList will be tested using strings only.
Specifically, the following methods must be implemented in the LinkedList class:
(You should utilize listIterator() method already defined in the LinkedList class to obtain its LinkedListIterator object, and use the methods in the LinkedListIterator class to traverse from the first element to the last element of the linked list to define the following methods.)
1.
public String toString()
The toString method should concatenate strings in the linked list, and return a string of the following format:
{ Apple Banana Melon Orange }
Thus it starts with "{" and ends with "}", and there is a space between strings and "{" or "}". If the list is empty, it returns "{ }" with a space in between. Note that all elements in the linked list will be added in alphabetical order.
2.
public int size()
The size method returns the number of strings that the linked list contains at the time when this method is called.
3.
public void addElement(Object element)
The addElement adds the parameter element into the linked list. The linked list should contain all elements (strings) in alphabetical order. Therefore, in this addElement method, a correct location to insert the parameter element needs to be searched and the element needs to be inserted in that location.
4.
public void removeElementsAtOddIndices( )
The removeElementsAtOddIndices should remove objects at odd indices within the linked list. For instance, if the linked list contains { Apple Banana Melon Orange }, then after calling this method, the linked list will contains { Apple Melon } since Banana at the index 1 and Orange at the index 3 need to be removed. Each element within the linked list will can be labeled starting the index 0, and based on this assumption, elements should be removed. If the linked list does not contain any element, or contains only one element, then the method should not change its content.
5.
public void removeAdditionalOccurrences(Object element)
The removeAdditionalOccurrences method should search the parameter object (a string in this case) in the linked list, then it should keep the first occurrence of the element, but it should remove any other elements that is same as the parameter object within the linked list if any. For instance, if the linked list contains { Apple Banana Banana Banana Melon Melon Orange }, then after calling removeAdditionalOccurrences(Banana), the linked list will become { Apple Banana Melon Melon Orange }.
6.
public Object searchByIndex(int index)
The searchByIndex method should look for an object of the given parameter index and return it. If the parameter index is larger or smaller than the existing indices, it should throw an object of the IndexOutOfBoundsException class.
7.
public void searchAndIncrease(Object element, int howMany)
The searchAndIncrease method should search the parameter object (a string), and if it is found, add the same object (a string) as many as the integer specified by the parameter howMany. For instance, if the linked list contains { Apple Banana Melon Orange }, and searchAndIncrease(Melon, 3) is called, then the linked list will contain { Apple Banana Melon Melon Melon Melon Orange } by adding Melon three times right after the found Melon. If the parameter element is not found in the linked list, or the value of howMany is 0 or less, then it should not change the content of the linked list.
Given Code
//////////////////////////////////////////
Assignment 10.java
///////////////////////////////////////////////////////////////////////
LinkedList.java
///////////////////////////////////////////////////////////
ListIterator.java
////////////////////////////////////////////////////
Test case #1
A
OutPut test case #1
Choice Action
/////////////////////////////////////////////////////////////
Input test case #2
Output Test case #2
///////////////////////////////////////////////////////////////
Please... really need help with this one.
Don't just post some smiliar codes....
Explanation / Answer
Bold code is modified given below:
//LinkedList.java
import java.util.NoSuchElementException;
public class LinkedList
{
int size = 0;
// nested class to represent a node
private class Node
{
public Object data;
public Node next;
}
// only instance variable that points to the first node.
private Node first;
// Constructs an empty linked list.
public LinkedList()
{
first = null;
}
// Returns the first element in the linked list.
public Object getFirst()
{
if (first == null)
{
NoSuchElementException ex = new NoSuchElementException();
throw ex;
}
else
{
return first.data;
}
}
// Removes the first element in the linked list.
public Object removeFirst()
{
if (first == null)
{
NoSuchElementException ex = new NoSuchElementException();
throw ex;
}
else
{
Object element = first.data;
first = first.next; // change the reference since it's removed.
return element;
}
}
// Adds an element to the front of the linked list.
public void addFirst(Object element)
{
// create a new node
Node newNode = new Node();
newNode.data = element;
newNode.next = first;
// change the first reference to the new node.
first = newNode;
}
// Returns an iterator for iterating through this list.
public ListIterator listIterator()
{
return new LinkedListIterator();
}
//The toString() method should concatenate strings in the linked list,
//and return a string of the format as {string1 string2 string3 ... ... ...}
public String toString()
{
String str = "";
if (size() == 0)
{
str = "{ } ";
}
else
{
str = "{ ";
StringBuilder sb = new StringBuilder();
ListIterator iterator = listIterator();
while (iterator.hasNext())
{
sb.append(String.valueOf(iterator.next())).append(" ");
}
sb.append("} ");
str = str.concat(sb.toString());
}
return str;
}
//size() method returns the number of strings that the linked list
//contains at the time when this method is called.
public int size()
{
int listsize = 0;
ListIterator iterator_list = listIterator();
while (iterator_list.hasNext())
{
iterator_list.next();
listsize++;
}
return listsize;
}
/*
* The addElementAt adds the parameter element at the parameter specified
* index. The element at the index and any elements at the later indices
* will be shifted towards the end of the list. If the parameter index is
* larger or smaller than the existing indices, it should throw an object
* of the IndexOutOfBoundsException class.
*/
public void addElementAt(Object element, int index)
{
try
{
LinkedListIterator iterator_list = new LinkedListIterator();
if (index == 0)
{
addFirst(element);
return;
}
else
{
if (index >= 0 || index < size)
{
for (int i = 0; i < index; i++)
{
iterator_list.next();
}
iterator_list.add(element);
size++;
}
else
{
IndexOutOfBoundsException ex = new IndexOutOfBoundsException();
throw ex;
}
}
}
catch (IndexOutOfBoundsException iobe)
{
System.out.print("Index out of bounds exception. ");
}
}
/* The addFewAtEnd method adds the parameter element at the end of the
* linked list for the number of times specified by the parameter
* 'howMany'
*/
public void addFewAtEnd(Object element, int howMany)
{
int i = 0;
int listSize = size();
while (i < howMany)
{
addElementAt(element, listSize);
listSize++;
i++;
}
}
/*
* The removeLastFew method removes the number of elements at the end
* of the linked list, which was specified by the parameter 'howMany'.
*/
public void removeLastFew(int howMany)
{
ListIterator listIterator = listIterator();
int listsize = size();
int i = 0;
if (howMany > 0)
{
if (howMany < listsize)
{
while (i < (listsize - howMany))
{
listIterator.next();
i++;
}
for (int r = 0; r < howMany; r++)
{
listIterator.next();
listIterator.remove();
}
}
else
{
while (i < listsize)
{
listIterator.next();
i++;
}
for (int r = 0; r < listsize; r++)
{
listIterator.remove();
}
}
}
}
// The removeAllOccurrences method removes all occurrences
// of the parameter string (object) in the list
public void removeAllOccurrences(Object stringToBeRemoved)
{
LinkedListIterator listiterator = new LinkedListIterator();
while (listiterator.hasNext())
{
if (listiterator.next().equals(stringToBeRemoved.toString()))
{
listiterator.remove();
}
}
}
/*
* The reverseLastFew method reverses the number of elements
* at the end of the linked list, which was specified by the
* parameter 'howMany'.
*/
public void reverseLastFew(int howMany)
{
ListIterator listiterator = this.listIterator();
int listsize = size();
int i = 0, count = 0;
LinkedList linkedList = new LinkedList();
if (howMany > 0)
{
if (howMany < listsize)
{
while (i < (listsize - howMany))
{
listiterator.next();
i++;
}
count = 0;
while (listiterator.hasNext())
{
String str = String.valueOf(listiterator.next());
linkedList.listIterator().add(str);
count++;
}
i = 0;
while (i < howMany)
{
removeLastFew(1);
i++;
}
i = 0;
while (i < howMany)
{
String str1 = String.valueOf(linkedList.getFirst());
this.addFewAtEnd(str1, 1);
linkedList.removeFirst();
i++;
}
}
else
{
count = 0;
while (listiterator.hasNext())
{
String str = String.valueOf(listiterator.next());
linkedList.listIterator().add(str);
System.out.println(str + "--");
count++;
}
i = 0;
while (i < listsize)
{
removeLastFew(1);
i++;
}
i = 0;
while (i < listsize)
{
String str1 = String.valueOf(linkedList.getFirst());
this.addFewAtEnd(str1, 1);
linkedList.removeFirst();
i++;
}
}
}
}
// nested class to define its iterator
private class LinkedListIterator implements ListIterator
{
private Node position; // current position
private Node previous; // it is used for remove() method
// Constructs an iterator that points to the front
// of the linked list.
public LinkedListIterator()
{
position = null;
previous = null;
}
// Tests if there is an element after the iterator position.
public boolean hasNext()
{
if (position == null) // not traversed yet
{
if (first != null)
{
return true;
}
else
{
return false;
}
}
else
{
if (position.next != null)
{
return true;
}
else
{
return false;
}
}
}
// Moves the iterator past the next element, and returns
// the traversed element's data.
public Object next()
{
if (!hasNext())
{
NoSuchElementException ex = new NoSuchElementException();
throw ex;
}
else
{
previous = position; // Remember for remove
if (position == null)
{
position = first;
}
else
{
position = position.next;
}
return position.data;
}
}
// Adds an element before the iterator position
// and moves the iterator past the inserted element.
public void add(Object element)
{
if (position == null) // never traversed yet
{
addFirst(element);
position = first;
}
else
{
// making a new node to add
Node newNode = new Node();
newNode.data = element;
newNode.next = position.next;
// change the link to insert the new node
position.next = newNode;
// move the position forward to the new node
position = newNode;
}
// this means that we cannot call remove() right after add()
previous = position;
}
// Removes the last traversed element. This method may
// only be called after a call to the next() method.
public void remove()
{
if (previous == position) // not after next() is called
{
IllegalStateException ex = new IllegalStateException();
throw ex;
}
else
{
if (position == first)
{
removeFirst();
}
else
{
previous.next = position.next; // removing
}
// stepping back this also means that remove() cannot be called twice
// in a row
position = previous;
}
}
// Sets the last traversed element to a different value.
public void set(Object element)
{
if (position == null)
{
NoSuchElementException ex = new NoSuchElementException();
throw ex;
}
else
{
position.data = element;
}
}
} // end of LinkedListIterator class
} // end of LinkedList class
//ListIterator.java
public interface ListIterator
{
//Move Moves the iterator past the next element.
Object next();
// Tests if there is an element after the iterator position.
boolean hasNext();
// Adds an element before the iterator position
// and moves the iterator past the inserted element.
void add(Object element);
// Removes the last traversed element. This method may
// only be called after a call to the next() method.
void remove();
// Sets the last traversed element to a different value.
void set(Object element);
}
//Assignment10.java
import java.io.*;
public class Assignment10
{
public static void main(String[] args)
{
char input1;
String inputInfo = new String();
int operation2;
String line = new String();
//create a linked list to be used in this method.
LinkedList list1 = new LinkedList();
try
{
// print out the menu
printMenu();
// create a BufferedReader object to read input from a keyboard
InputStreamReader isr = new InputStreamReader (System.in);
BufferedReader stdin = new BufferedReader (isr);
do
{
System.out.print("What action would you like to perform? ");
line = stdin.readLine().trim(); //read a line
input1 = line.charAt(0);
input1 = Character.toUpperCase(input1);
if (line.length() == 1) //check if a user entered only one character
{
switch (input1)
{
case 'A': //Add String
System.out.print("Please enter a string to add: ");
String str1 = stdin.readLine().trim();
System.out.print("Please enter its index: ");
int index = Integer.parseInt(stdin.readLine().trim());
try
{
list1.addElementAt(str1, index);
}
catch(IndexOutOfBoundsException ex)
{
System.out.print("The index is out of bounds ");
}
break;
case 'B': //Add Strings at End
System.out.print("Please enter a string to add at the end: ");
String str2 = stdin.readLine().trim();
System.out.print("Please enter a number of times to add: ");
String times = stdin.readLine().trim();
int howMany = Integer.parseInt(times);
list1.addFewAtEnd(str2, howMany);
break;
case 'C': //Count the size of the linked list
int size = list1.size();
System.out.print("The size of the linked list is " + size + " ");
break;
case 'L': //List Strings
System.out.print(list1.toString());
break;
case 'Q': //Quit
break;
case 'R': //Remove Strings from end
System.out.print("Please enter a number of elements to remove from the end: ");
inputInfo = stdin.readLine().trim();
int howMany2 = Integer.parseInt(inputInfo);
list1.removeLastFew(howMany2);
break;
case 'S': //Remove String from List
System.out.print("Please enter a string to remove from the linked list: ");
inputInfo = stdin.readLine().trim();
list1.removeAllOccurrences(inputInfo);
break;
case 'T': //Reverse Strings from End
System.out.print("Please enter a number of elements to reverse from the end: ");
inputInfo = stdin.readLine().trim();
int howMany3 = Integer.parseInt(inputInfo);
list1.reverseLastFew(howMany3);
break;
case '?': //Display Menu
printMenu();
break;
default:
System.out.print("Unknown action ");
break;
}
}
else
{
System.out.print("Unknown action ");
}
} while (input1 != 'Q' || line.length() != 1);
}
catch (IOException exception)
{
System.out.print("IO Exception ");
}
}
public static void printMenu()
{
System.out.print("Choice Action " +
"------ ------ " +
"A Add String " +
"B Add Strings at End " +
"C Count its Size " +
"L List Strings " +
"Q Quit " +
"R Remove Strings from End " +
"S Remove String from List " +
"T Reverse Strings from End " +
"? Display Help ");
} //end of printMenu()
}