Java – Exception in thread "main" java.lang.Error: Unresolved compilation problem

I am trying to implement a linked list using in Java, but I keep getting this error in my VSCode terminal.
Exception in thread "main" java.lang.Error: Unresolved compilation problem: The method reverse() is undefined for the type SinglyLinkedList
I have two files, reverseSLL.java and removeDupesFromSLL.java. reverseSLL works perfectly fine if I delete the removeDupesFromSLL file from src folder. Can anyone please explain what I am doing wrong?
Here is the code reverseSLL.java:

class SinglyLinkedList{
    int data;
    SinglyLinkedList next;
    SinglyLinkedList head = null;

    public void add(int data){
        SinglyLinkedList newNode = new SinglyLinkedList();
        newNode.data = data;
        newNode.next = null;

        if(head == null){
            head = newNode;
        }
        else{
            SinglyLinkedList temp = head;
            while(temp.next != null){
                temp = temp.next;
            }
            temp.next = newNode;
        }
    }

    public void print(){
        SinglyLinkedList temp = head;
        while(temp != null){
            System.out.print(temp.data + " ");
            temp = temp.next;
        }
        System.out.println();
    }
    
    public void reverse(){
        SinglyLinkedList prev = null;
        SinglyLinkedList current = head;
        SinglyLinkedList next = null;
        while(current != null){
            next = current.next;
            current.next = prev;
            prev = current;
            current = next;
        }
        head = prev;
    }
}
public class reverseSLL {
    public static void main(String[]args){
        SinglyLinkedList sll = new SinglyLinkedList();
        sll.add(1);
        sll.add(2);
        sll.add(3);
        sll.add(4);
        sll.add(5);
        
        sll.print();    
        sll.reverse();
        sll.print();
    }
}

Code of RemoveDupesFromSLL.java:

class SinglyLinkedList{
    int data;
    SinglyLinkedList next;
    SinglyLinkedList head = null;

    public void add(int data){
        SinglyLinkedList newNode = new SinglyLinkedList();
        newNode.data = data;
        newNode.next = null;

        if(head == null){
            head = newNode;
        }
        else{
            SinglyLinkedList temp = head;
            while(temp.next != null){
                temp = temp.next;
            }
            temp.next = newNode;
        }
    }

    public void print(){
        SinglyLinkedList temp = head;
        while(temp != null){
            System.out.print(temp.data + " ");
            temp = temp.next;
        }
        System.out.println();
    }

    public void sort(){
        SinglyLinkedList temp = head;
        while(temp != null){
            SinglyLinkedList temp2 = temp.next;
            while(temp2 != null){
                if(temp.data > temp2.data){
                    int tempData = temp.data;
                    temp.data = temp2.data;
                    temp2.data = tempData;
                }
                temp2 = temp2.next;
            }
            temp = temp.next;
        }
    }

    public void removeDuplicates(){
        SinglyLinkedList ptr = head;
        while(ptr.next != null){
            if(ptr.data == ptr.next.data) ptr.next = ptr.next.next;
            else ptr = ptr.next;
        }
    }
}

class removeDupesFromSLL{
    public static void main(String[]args){
        SinglyLinkedList sll = new SinglyLinkedList();
        sll.add(2);
        sll.add(3);
        sll.add(4);
        sll.add(1);
        sll.add(4);
        sll.add(5);
        sll.add(5);
        
        sll.print();    
        sll.sort();
        sll.print();
        sll.removeDuplicates();
        sll.print();
    }
}

>Solution :

The error is telling you exactly the problem:

The method reverse() is undefined for the type SinglyLinkedList

this means your class SinglyLinkedList doesnt have the method reverse().

The problem here is that SinglyLinkedList exists two times. You should rename them to be distinct and then the error will help you.