Lab 20 Removing the first element in a list Start this lab with the code listed below. The LinkedList class defines the rudiments of the code needed to build a linked list of Nodes. Complete the code for the removeFirst method, which should remove and return the first element in the linked list. Throw a NoSuchElementException if the method is invoked on an empty list. Use the LinkedListRunner class’s main method to test your code. import java.util.NoSuchElementException; public class LinkedList { private Node first; public LinkedList() { first = null; } public Object getFirst() { if (first == null) { throw new NoSuchElementException(); } return first.data; } public void addFirst(Object element) { Node aNode = new Node(); aNode.data = element; aNode.next = first; first = aNode; } public Object removeFirst() { // put your code here } public String toString() { String temp = ""; Node current = first; while (current != null) { temp = temp + current.data.toString() + '\n'; current = current.next; } return temp; } class Node { public Object data; public Node next; } } ----------------------------------- public class LinkedListRunner { public static void main(String[] args) { LinkedList myList = new LinkedList(); myList.addFirst("aaa"); myList.addFirst("bbb"); myList.addFirst("ccc"); myList.addFirst("ddd"); System.out.println(myList); System.out.println("Removed element: " + myList.removeFirst()); System.out.println("Removed element: " + myList.removeFirst()); System.out.println(myList); } }

Lab 20 Removing the first element in a list Start this lab with the code listed below. The LinkedList class defines the rudiments of the code needed to build a linked list of Nodes. Complete the code for the removeFirst method, which should remove and return the first element in the linked list. Throw a NoSuchElementException if the method is invoked on an empty list. Use the LinkedListRunner class’s main method to test your code. import java.util.NoSuchElementException; public class LinkedList { private Node first; public LinkedList() { first = null; } public Object getFirst() { if (first == null) { throw new NoSuchElementException(); } return first.data; } public void addFirst(Object element) { Node aNode = new Node(); aNode.data = element; aNode.next = first; first = aNode; } public Object removeFirst() { // put your code here } public String toString() { String temp = ""; Node current = first; while (current != null) { temp = temp + current.data.toString() + '\n'; current = current.next; } return temp; } class Node { public Object data; public Node next; } } ----------------------------------- public class LinkedListRunner { public static void main(String[] args) { LinkedList myList = new LinkedList(); myList.addFirst("aaa"); myList.addFirst("bbb"); myList.addFirst("ccc"); myList.addFirst("ddd"); System.out.println(myList); System.out.println("Removed element: " + myList.removeFirst()); System.out.println("Removed element: " + myList.removeFirst()); System.out.println(myList); } }

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Lab 20 Removing the first element in a list

Start this lab with the code listed below. The LinkedList class defines the rudiments of the code needed to build a linked list of Nodes. Complete the code for the removeFirst method, which should remove and return the first element in the linked list. Throw a NoSuchElementException if the method is invoked on an empty list. Use the LinkedListRunner class’s main method to test your code.

import java.util.NoSuchElementException;

public class LinkedList
{
   private Node first;

   public LinkedList() { first = null; }

   public Object getFirst()
   {
      if (first == null) { throw new NoSuchElementException(); }
      return first.data;
   }

   public void addFirst(Object element)
   {
       Node aNode = new Node();
       aNode.data = element;
       aNode.next = first;
       first = aNode;

   }

   public Object removeFirst()
   {
      // put your code here
   }

   public String toString()
   {
      String temp = "";
      Node current = first;
      while (current != null)
      {
         temp = temp + current.data.toString() + '\n';
         current = current.next;
      }
      return temp;
   }

   class Node
   {
      public Object data;
      public Node next;
   }
}

-----------------------------------

public class LinkedListRunner
{
   public static void main(String[] args)
   {
       LinkedList myList = new LinkedList();
       myList.addFirst("aaa");
       myList.addFirst("bbb");
       myList.addFirst("ccc");
       myList.addFirst("ddd");
       System.out.println(myList);
       System.out.println("Removed element: " + myList.removeFirst());
       System.out.println("Removed element: " + myList.removeFirst());
       System.out.println(myList);
   }
}

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