Delete Node at End in DSA Java - Build from Scratch

Delete Node at End in a Singly Linked List

📖 Scenario: You are managing a simple list of tasks using a singly linked list. Each task is a node with a number. You want to remove the last task from the list when it is completed.

🎯 Goal: Build a Java program that creates a singly linked list with 3 nodes, then deletes the last node, and finally prints the list.

📋 What You'll Learn

Create a singly linked list with nodes containing values 10, 20, and 30

Create a method to delete the last node from the list

Print the list after deletion showing the remaining nodes

💡 Why This Matters

🌍 Real World

Linked lists are used in many applications like task scheduling, undo functionality, and managing playlists where items are added or removed dynamically.

💼 Career

Understanding linked lists and how to manipulate nodes is fundamental for software developers working with data structures, memory management, and algorithm optimization.

1

Create the Singly Linked List with 3 Nodes

Create a class called Node with an integer data and a Node reference called next. Then create a class called LinkedList with a Node variable called head. In the main method, create a LinkedList object called list and add three nodes with values 10, 20, and 30 linked in order.

DSA Java

// Define Node and LinkedList classes
// Create LinkedList object called list
// Add nodes with data 10, 20, 30 linked in order
// Your code here

Hint

Start by defining the Node class with data and next. Then create the LinkedList class with a head node. In main, create the list and link the nodes.

2

Add a Method to Delete the Last Node

Inside the LinkedList class, add a method called deleteAtEnd() that deletes the last node from the list. Handle the case when the list is empty or has only one node.

DSA Java

class Node {
    int data;
    Node next;
    Node(int data) {
        this.data = data;
        this.next = null;
    }
}

class LinkedList {
    Node head;
    // Add deleteAtEnd method here
    // Your code here
}

public class Main {
    public static void main(String[] args) {
        LinkedList list = new LinkedList();
        list.head = new Node(10);
        list.head.next = new Node(20);
        list.head.next.next = new Node(30);
    }
}

Hint

Check if the list is empty or has one node. If not, loop to the second last node and set its next to null.

3

Call the deleteAtEnd Method

In the main method, after creating the list, call the deleteAtEnd() method on the list object to remove the last node.

DSA Java

class Node {
    int data;
    Node next;
    Node(int data) {
        this.data = data;
        this.next = null;
    }
}

class LinkedList {
    Node head;

    void deleteAtEnd() {
        if (head == null) {
            return; // List is empty
        }
        if (head.next == null) {
            head = null; // Only one node
            return;
        }
        Node current = head;
        while (current.next.next != null) {
            current = current.next;
        }
        current.next = null; // Remove last node
    }
}

public class Main {
    public static void main(String[] args) {
        LinkedList list = new LinkedList();
        list.head = new Node(10);
        list.head.next = new Node(20);
        list.head.next.next = new Node(30);
        // Call deleteAtEnd method here
        // Your code here
    }
}

Hint

Simply call list.deleteAtEnd(); after creating the nodes.

4

Print the List After Deletion

Add a method called printList() inside the LinkedList class that prints all node values separated by -> and ends with null. Then call printList() in the main method after deleting the last node.

DSA Java

class Node {
    int data;
    Node next;
    Node(int data) {
        this.data = data;
        this.next = null;
    }
}

class LinkedList {
    Node head;

    void deleteAtEnd() {
        if (head == null) {
            return; // List is empty
        }
        if (head.next == null) {
            head = null; // Only one node
            return;
        }
        Node current = head;
        while (current.next.next != null) {
            current = current.next;
        }
        current.next = null; // Remove last node
    }

    // Add printList method here
    // Your code here
}

public class Main {
    public static void main(String[] args) {
        LinkedList list = new LinkedList();
        list.head = new Node(10);
        list.head.next = new Node(20);
        list.head.next.next = new Node(30);
        list.deleteAtEnd();
        // Call printList method here
        // Your code here
    }
}

Hint

Loop through the list printing each node's data followed by -> . End with null. Call this method after deleting the last node.

Practice

1. What does the operation Delete Node at End do in a singly linked list?

easy

A. Removes the last node from the list

B. Removes the first node from the list

C. Adds a new node at the end of the list

D. Adds a new node at the beginning of the list

Solution

1. Step 1: Understand the operation meaning

   Deleting a node at the end means removing the last node in the linked list.

2. Step 2: Identify the correct description

   Removing the last node matches Removes the last node from the list, while others describe adding or removing nodes at different positions.

3. Final Answer:

   Removes the last node from the list -> Option A

4. Quick Check:

   Delete Node at End = Removes last node [OK]

Hint: Deleting at end always removes the last node [OK]

Common Mistakes:

• Confusing delete at end with delete at beginning
• Thinking it adds a node instead of removing
• Mixing up first and last node operations

2. Which of the following is the correct Java syntax to delete the last node in a singly linked list named list assuming you have a method deleteAtEnd()?

easy

A. list.deleteAtEnd();

B. deleteAtEnd.list();

C. list.deleteAtEnd;

D. list.deleteAtEnd[];

Solution

1. Step 1: Identify method call syntax in Java

   Calling a method on an object uses dot notation with parentheses: object.methodName();

2. Step 2: Match correct syntax

   list.deleteAtEnd(); uses correct syntax: list.deleteAtEnd(); others have syntax errors or wrong usage.

3. Final Answer:

   list.deleteAtEnd(); -> Option A

4. Quick Check:

   Method call syntax = object.method() [OK]

Hint: Method calls need parentheses after name [OK]

Common Mistakes:

• Omitting parentheses when calling methods
• Using brackets [] instead of parentheses ()
• Reversing object and method names

3. Consider the following Java code for a singly linked list:

class Node {
  int data;
  Node next;
  Node(int d) { data = d; next = null; }
}

class LinkedList {
  Node head;

  void deleteAtEnd() {
    if (head == null) return;
    if (head.next == null) {
      head = null;
      return;
    }
    Node temp = head;
    while (temp.next.next != null) {
      temp = temp.next;
    }
    temp.next = null;
  }

  void printList() {
    Node temp = head;
    while (temp != null) {
      System.out.print(temp.data + " -> ");
      temp = temp.next;
    }
    System.out.println("null");
  }
}

public class Main {
  public static void main(String[] args) {
    LinkedList list = new LinkedList();
    list.head = new Node(1);
    list.head.next = new Node(2);
    list.head.next.next = new Node(3);
    list.deleteAtEnd();
    list.printList();
  }
}

What is the output after running this code?

medium

A. 1 -> 2 -> 3 -> null

B. 1 -> 2 -> null

C. 2 -> 3 -> null

D. null

Solution

1. Step 1: Understand initial list and deleteAtEnd()

   The list starts as 1 -> 2 -> 3 -> null. The deleteAtEnd() removes the last node (3).

2. Step 2: Trace deleteAtEnd() method

   It traverses to node with data 2, sets its next to null, removing node 3.

3. Final Answer:

   1 -> 2 -> null -> Option B

4. Quick Check:

   Last node removed, list ends at 2 [OK]

Hint: Deleting end removes last node, list shortens by one [OK]

Common Mistakes:

• Forgetting to update the second last node's next to null
• Assuming head changes when list has multiple nodes
• Printing old list without deletion

4. The following Java method is intended to delete the last node of a singly linked list. What is the error?

void deleteAtEnd() {
  if (head == null) return;
  Node temp = head;
  while (temp.next != null) {
    temp = temp.next;
  }
  temp = null;
}

medium

A. It causes a NullPointerException

B. It does not handle empty list

C. It deletes the head node incorrectly

D. It does not update the second last node's next pointer

Solution

1. Step 1: Analyze the loop and pointer updates

   The loop moves temp to the last node (where temp.next is null). Setting temp = null only changes local pointer, not list links.

2. Step 2: Identify missing update to second last node

   The second last node's next pointer is not set to null, so the last node remains linked.

3. Final Answer:

   It does not update the second last node's next pointer -> Option D

4. Quick Check:

   Must update second last node's next to null [OK]

Hint: Set second last node's next to null, not just temp = null [OK]

Common Mistakes:

• Setting temp = null only changes local variable
• Not handling single-node list case
• Ignoring list head update if only one node

5. You have a singly linked list with nodes containing values: 10 -> 20 -> 30 -> 40 -> null. You want to delete the last node and then add a new node with value 50 at the end. Which sequence of operations correctly achieves this?

hard

A. Call addAtEnd(50) only

B. Call addAtEnd(50), then call deleteAtEnd()

C. Call deleteAtEnd(), then call addAtEnd(50)

D. Call deleteAtEnd() twice, then addAtEnd(50)

Solution

1. Step 1: Delete the last node

   Calling deleteAtEnd() removes node with value 40, list becomes 10 -> 20 -> 30 -> null.

2. Step 2: Add new node with value 50 at end

   Calling addAtEnd(50) appends node 50, list becomes 10 -> 20 -> 30 -> 50 -> null.

3. Final Answer:

   Call deleteAtEnd(), then call addAtEnd(50) -> Option C

4. Quick Check:

   Delete last, then add new node [OK]

Hint: Delete old last node before adding new one [OK]

Common Mistakes:

• Adding new node before deleting old last node
• Deleting twice unnecessarily
• Not deleting at all before adding