import java.util.NoSuchElementException; import java.util.Scanner; /** * Questio

Question

import java.util.NoSuchElementException;
import java.util.Scanner;

/**
* Question 10:
*
* Finish the implementation of the deleteHead() method.
* This method will remove the head (first element) of the list and
* return the head node's value.
* deleteHead() should throw a NoSuchElementException if the
* list is empty.
*
* For instance, given the list
* 1 2 3
* deleteHead() would return 1 and the list would then look like this:
* 2 3
*
* You will also need to add the "addToEnd()" method that you
* wrote in question 5. You can simply copy and paste that
* into this class.
*
* Only add code in between the comments that say
* "Begin your code here"
* and
* "End your code here"
*
* or immediately after
* "Paste addToEnd() method here"
*/

public class LinkedList10 {
   // Private inner class Node
  
   private class Node{
       int data;
   Node link;
  
   @SuppressWarnings("unused")
       public Node(){
       data = Integer.MIN_VALUE;
       link = null;
   }
  
   public Node(int x, Node p){
       data = x;
       link = p;
   }
   }
   // End of Node class
  
   public Node head;
  
   public LinkedList10(){
       head = null;
   }
  
   public int deleteHead() throws NoSuchElementException {
       /** Begin your code here **/
      
       /** end your code here **/
   }
  
   /** Paste addToEnd() method here **/
   public void addToEnd(int data) {
       /** Begin your code here **/
       if(head == null)
       {
       head = new Node(data, head);
       }
       else
       {
       Node position = head;
       while(position.link != null)
       {
       position = position.link;
       }
       position.link = new Node(data, null);
       }
       /** end your code here **/
   }

   public void printList(){
       Node position = head;
       if (head == null)
           System.out.println("The list is empty.");
       while(position != null){
           System.out.print(position.data + " ");
           position = position.link;
       }
       System.out.println();
   }
  
   public static void main(String[] args) {
       Scanner input = new Scanner(System.in);
       LinkedList10 list = new LinkedList10();
      
       list.printList();
      
       try {
           System.out.println("Deleting " + list.deleteHead());
       } catch (NoSuchElementException e) {
           System.out.println("Can't delete. The list is empty!");
       }
      
       System.out.println("How many values do you want to add to the list?");
       int toAdd = input.nextInt();
       for(int i = 0; i < toAdd; i++) {
           System.out.println("Enter value " + (i + 1));
           list.addToEnd(input.nextInt());
       }
      
       list.printList();
      
       try {
           System.out.println("Deleting " + list.deleteHead());
       } catch (NoSuchElementException e) {
           System.out.println("Can't delete. The list is empty!");
       }
      
       list.printList();

       input.close();
   }
}

Explanation / Answer

LinkedList10.java

import java.util.NoSuchElementException;//package for Exception class
import java.util.Scanner;//keyboard inputting class

public class LinkedList10 {
    public int data;//data
    public Node head;
    // Private inner class Node

    private class Node{
        int data;//data value for node
        Node link;//address for next node

        @SuppressWarnings("unused")
        public Node(){//constructor with out any arguments
            data = Integer.MIN_VALUE;
            link = null;
        }

        public Node(int x, Node p){
            data = x;//constructor with two args
            link = p;
        }
    }
    // End of Node class

    public LinkedList10(){
        head = null;
    }

    public int deleteHead() throws NoSuchElementException {
        /** Begin your code here **/
    if (head == null) throw new NoSuchElementException();

      int o = head.data;//returns the headdata

     head = head.link;//addressof head

     data--;//deleiting head data

   return o;

    }
    /** Paste addToEnd() method here **/
    public void addToEnd(int data) {
        /** Begin your code here **/
        if(head == null)
        {
            head = new Node(data, head);//adding data if head is null
        }
        else
        {
            Node position = head;
            while(position.link != null)
            {//inserting data to the end of the node
                position = position.link;
            }
            position.link = new Node(data, null);
        }
        /** end your code here **/
    }

    public void printList(){//ddisplay values
        Node position = head;
        if (head == null)
            System.out.println("The list is empty.");
        while(position != null){
            System.out.print(position.data + " ");
            position = position.link;
        }
        System.out.println();
    }

    public static void main(String[] args) {//driver program
        Scanner input = new Scanner(System.in);//keyboard inputting
        LinkedList10 list = new LinkedList10();

        list.printList();

        try {
            System.out.println("Deleting " + list.deleteHead());//calling deletehead
        } catch (NoSuchElementException e) {
            System.out.println("Can't delete. The list is empty!");
        }
System.out.println("How many values do you want to add to the list?");
        int toAdd = input.nextInt();
        for(int i = 0; i < toAdd; i++) {
            System.out.println("Enter value " + (i + 1));//addingvalues to node
            list.addToEnd(input.nextInt());
        }
     
        try {
            System.out.println("Deleting " + list.deleteHead());//calling deleteHead
        } catch (NoSuchElementException e) {
            System.out.println("Can't delete. The list is empty!");
        }

        list.printList();//displaay values

        input.close();
    }
}

output

The list is empty.

Can't delete. The list is empty!
How many values do you want to add to the list?
5
Enter value 1
23
Enter value 2
12
Enter value 3
1
Enter value 4
56
Enter value 5
7
Deleting 23
12 1 56 7

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