Single Linked List (Java assignment )

Today's you will write a program with three classes, the first class will be the driver, second will be the LinkedList class, and the third will be the Node class that will be holding the data.

The first class, Driver class will just create an instance of the Linked List class and then control the flow of the program.

The Second class with be the Node class, this is where you store each individual Student's name which is your data, it will have:

Two private variables (no need for a new class, just put the name in the Node class):

A String to hold the name of the student

Node next

A setNext() method that will allow you to set the reference of the instance variable next.

A getNext() method that will return the Item that next is referencing.

A toString() method to print out the name of the student

A getName() to return the name for comparison

All names will be initialized in constructor and you don't need methods to change them, just retrieve them for printing or searching.

The second class will be the class that manages the linked list that is made up of the Node objects. The LinkedList Class will contain:

An instance field Node reference to the first Node object in the list. (starts null for empty list)

Then you will need methods for handling all the menu choices in the driver.

Note: After you get one of the print or delete methods working the traversal is the same for both of them.

All items will be added to the end of the list, not the front.

Clear the list is just setting the correct reference to null, very simple. all of the other methods I did on the board.

The third class is the Driver, just like my example, should contain:

A menu that calls a method that is an infinite do/while loop until the user gives -1 to exit.

Inside the loop you should print a menu and then wait for user input.

Methods for printing the menu:

What would you like to do? Press 1 to add an item to the back of the list Press 2 to print the list Press 3 to delete an item Press 4 to clear the whole list Press -1 to exit 

The input from the user should go into a switch statement that switches for each input:

case 1:

linkedlist.addItem(node);

. The menu method should consistently run until the user gives a -1.

You are to implement a linked list of the Node objects. Singular linked list. Assume new objects are always added to the back of the list.

Make sure you handle special cases such as adding an item to an empty list, deleting the first, etc. etc.

This my code and I have problem with print method and clear the whole list.

import java.util.Scanner;

//Class Node definition

class Node

{

//Instance variable to store value of type integer

protected String studentName;

//Node class object created to store its own reference

//Instance variable to point to a node

protected Node next;

//Default constructor to initialize

public Node()

{

//Object is initialized to null

next = null;

//studentName is initialized to null

studentName = "";

}//End of constructor

//Parameterized constructor to initialize with specific value

public Node(String name, Node n)

{

//value is assigned with name value

studentName = name;

//Points to new node

next = n;

}//End of constructor

//Method to set link to next Node

public void setNext(Node n)

{

next = n;

}//End of method

//Method to get link to next node

public Node getNext()

{

//Returns the current reference

return next;

}//End of method

//Method to get data from current Node

public String getName()

{

//Return the current node data

return studentName;

}//End of method

}//End of class Node

//Class linkedList definition

class linkedList

{

//Reference object to point to starting node

protected Node start;

//Reference object to point to last node

protected Node end ;

//To store the size of the list

public int size;

//Default constructor to initialize

public linkedList()

{

//Start and last object is initialized to null

start = null;

end = null;

//Size is initialized to zero

size = 0;

}//End of constructor

//Method to check if list is empty

public boolean isEmpty()

{

//Returns true if the list is empty

return start == null;

}//End of method

//Method to insert a node at the end

public void insertAtEnd(String name)

{

//Creates a new node

Node newNode = new Node(name, null);

//Increases the size by one

size++ ;

//Checks if start is null then it is the first node

if(start == null)

{

//Start is pointing to new node

start = newNode;

end = start;

}//End of if

else

{

//end pointing to new node

end.setNext(newNode);

//New node reference to end node

end = newNode;

}//End of else

}//End of method

//Method to delete a node at position

public void deleteAtPos(int pos)

{

//Checks if the specified position is one for starting node

if (pos == 1)

{

start = start.getNext();

//size is reduced by one

size--;

return ;

}//End of if

//Checks if the position is equal to size for last node

if (pos == size)

{

//Creates a reference to refer to start node

Node sNode = start;

//Creates a temporary reference to refer to start node

Node tNode = start;

//Loops till end of the list

while (sNode != end)

{

//Assigns start node reference to temporary node

tNode = sNode;

//Points to next node

sNode = sNode.getNext();

}//End of while loop

//Temporary node reference is assigned to end node

end = tNode;

//End points to null

end.setNext(null);

//Reduce the size by one

size --;

return;

}//End of if

//For other than first or last

//Creates a reference to start node

Node ptr = start;

//Decrease the position by one because it starts from zero

pos = pos - 1 ;

//Loops till end of list

for (int counter = 1; counter < size - 1; counter++)

{

//Checks if the counter value is equal to position specified

if (counter == pos)

{

//Creates a temporary reference refers to next node

Node tmpNode = ptr.getNext();

//Temporary node refers to next node

tmpNode = tmpNode.getNext();

ptr.setNext(tmpNode);

break;

}//End of if

ptr = ptr.getNext();

}//End of for loop

//Decrease the size by one

size-- ;

}//End of method

//Method to display elements of the list

public void print()

{

System.out.print(" Linked List Contents ");

//Checks if the size is zero

if (size == 0)

{

//Displays the error message empty

System.out.print("ERROR: Empty list ");

return;

}//End of if

//If only one node

else if (start.getNext() == null)

{

//Displays the node value

System.out.println(start.getName() );

return;

}//End of if

//Creates a temporary reference to refer to start node

Node tempNode = start;

//Display the value of the start node

System.out.print(start.getName()+ "->");

//Points to the next node

tempNode = start.getNext();

//Loops till not null

while (tempNode.getNext() != null)

{

//Display the value of the current node

System.out.print(tempNode.getName()+ "->");

//Points to the next node

tempNode = tempNode.getNext();

}//End of while loop

System.out.print(tempNode.getName()+ " ");

}//End of method

//Method to delete all nodes

void deleteAll()

{

//Start is initialized to null

start = null;

//Set the size to zero

size = 0;

}

}//End of classLinkedList

//Driver class LinkedListDriver definition

public class LinkedListDriver

{

//Displays menu

static void menu()

{

System.out.println(" What would you like to do?" +

" Press 1 to add an item to the back of the list " +

" Press 2 to print the list" +

" Press 3 to delete an item" +

" Press 4 to clear the whole list" +

" Press -1 to exit");

System.out.println(" Enter your choice: ");

}//End of method

//main method definition

public static void main(String[] args)

{

//Scanner class object created

Scanner sc = new Scanner(System.in);

//Creating object of class linkedList

linkedList list = new linkedList();

//Loops till -1 is entered

do

{

//Displays menu

menu();

//Accepts user choice

int choice = sc.nextInt();

//Switch case begins

switch(choice)

{

case 1:

System.out.print(" Enter a name to insert: ");

list.insertAtEnd(sc.next());

break;

case 2:

list.print();

break;

case 3:

System.out.print(" Enter the position to delete: ");

list.deleteAtPos(sc.nextInt());

break;

case 4:

list.deleteAll();

break;

case -1:

System.exit(0);

default:

System.out.println("Invalid choice.");

}//End of switch - case

}while(true);

}

}