Question

Could you double check my program? I cannot get it to run. If you could tell me any changes that need to be made as well show the output I would greatly appreciate it.

LinkedList.java

public class LinkedList
{

class Node{
int value;
Node nextElement;

public Node(int value) {
this.value = value;
this.nextElement = null;
}
}

public Node first = null;
public Node last = null;

public void addNewNode(int element) {

Node newValueNode = new Node(element);

if(first == null) {

first = newValueNode;
}
else {
last.nextElement = newValueNode;
}
last = newValueNode;
}

public void displayValues() {
Node recent = first;

if(first == null) {
System.out.println("The list is currently Empty ");
return;
}
System.out.println("Nodes are : ");
while(recent != null) {

System.out.print(recent.value + " ");
recent = recent.nextElement;
}
System.out.println();
}

public int getPeek(){
Node temp = first;
return temp.value;
}

public int lengthOfLinkedList()
{
Node temp = first;
int count = 0;
while (temp != null)
{
temp = temp.nextElement;
count++;
}
return count;
}

public void deleteValue(int key)
{

Node temp = first, prev = null;

if (temp != null && temp.value == key)
{
first = temp.nextElement;
return;
}

while (temp != null && temp.value != key)
{
prev = temp;
temp = temp.nextElement;
}

if (temp == null) return;
prev.nextElement = temp.nextElement;
}

public static void main(String[] args) {
LinkedList valueList = new LinkedList();

valueList.addNewNode(1);
valueList.addNewNode(2);
valueList.addNewNode(3);
valueList.addNewNode(4);
valueList.addNewNode(5);

System.out.println("The LinkedList Consist Of The Following :" + valueList.lengthOfLinkedList());
valueList.displayValues();
valueList.deleteValue(3);
System.out.println("After Deleting, The LinkedList Consist Of :" + valueList.lengthOfLinkedList());
valueList.displayValues();
System.out.println("1st Item : " + valueList.getPeek());
}
}

Answer 1

I think you forgot to import the java.util.* file in your program. After importing the java.util.* file in the program, the program runs perfectly fine and output is printed and attached below.

Updated Code:

import java.util.*;

public class LinkedList {
   class Node {
       int value;
       Node nextElement;

       public Node(int value) {
           this.value = value;
           this.nextElement = null;
       }
   }

   public Node first = null;
   public Node last = null;

   public void addNewNode(int element) {

       Node newValueNode = new Node(element);

       if (first == null) {

           first = newValueNode;
       } else {
           last.nextElement = newValueNode;
       }
       last = newValueNode;
   }

   public void displayValues() {
       Node recent = first;

       if (first == null) {
           System.out.println("The list is currently Empty ");
           return;
       }
       System.out.println("Nodes are : ");
       while (recent != null) {

           System.out.print(recent.value + " ");
           recent = recent.nextElement;
       }
       System.out.println();
   }

   public int getPeek() {
       Node temp = first;
       return temp.value;
   }

   public int lengthOfLinkedList() {
       Node temp = first;
       int count = 0;
       while (temp != null) {
           temp = temp.nextElement;
           count++;
       }
       return count;
   }

   public void deleteValue(int key) {

       Node temp = first, prev = null;

       if (temp != null && temp.value == key) {
           first = temp.nextElement;
           return;
       }

       while (temp != null && temp.value != key) {
           prev = temp;
           temp = temp.nextElement;
       }

       if (temp == null) return;
       prev.nextElement = temp.nextElement;
   }

   public static void main(String[] args) {
       LinkedList valueList = new LinkedList();

       valueList.addNewNode(1);
       valueList.addNewNode(2);
       valueList.addNewNode(3);
       valueList.addNewNode(4);
       valueList.addNewNode(5);

       System.out.println("The LinkedList Consist Of The Following :" + valueList.lengthOfLinkedList());
       valueList.displayValues();
       valueList.deleteValue(3);
       System.out.println("After Deleting, The LinkedList Consist Of :" + valueList.lengthOfLinkedList());
       valueList.displayValues();
       System.out.println("1st Item : " + valueList.getPeek());
   }
}

Screenshot of the code:

OUTPUT:

The LinkedList Consist Of The Following :5
Nodes are :
1 2 3 4 5
After Deleting, The LinkedList Consist Of :4
Nodes are :
1 2 4 5
1st Item : 1

Screenshot of output:

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