Thread: Sorting ascending/descending methods not working on double linked list

Hi there. I'd like some help with the following code. I wrote displayAscending() and displayDescending() methods to this double linked list and it is not working at all. Logically it seems fine to me. I positioned the head in the beginning in the ascending method; created a variable named data1 as an auxiliar variable so it can store the values that are going to be moved; and moved the values. Same thing for the descending method but instead of the head I put the tail and move left the list, instead of right. I'd really appreciate some help because I've been stuck here for hours. Thank you

import java.util.*;
 
class node {
 
    int data;
    node left;
    node right;
 
    node(int d, node l, node r) {
        data = d;
        left = l;
        right = r;
    }
}
 
class Link {
 
    node head;
    node tail;
 
    public void insertfront(int data) {
        int flag = 0;
        node newnode = new node(data, null, null);
        if (head == null) {
            head = newnode;
            tail = head;
            tail.right = head;
            head.left = tail;
            flag = 1;
        } else {
            newnode.right = head;
            newnode.left = tail;
            tail.right = newnode;
            head = newnode;
            flag = 1;
        }
        if (flag == 1) {
            System.out.println("element " + data + "is inserted.");
        } else {
            System.out.println("element " + data + "is not inserted.");
        }
    }
 
    public void insertend(int data) {
        node newnode = new node(data, null, null);
        node current = head;
        while (current.right != head) {
            current = current.right;
        }
        current.right = newnode;
        newnode.left = current;
        newnode.right = head;
        tail = newnode;
    }
 
    public void insertatPosition(int data, int pos) {
        node newnode = new node(data, null, null);
        node current = head;
        node previous = head;
        int i = 1;
        while (i != (pos - 1)) {
            current = current.right;
            i++;
        }
        newnode.right = current.right;
        newnode.left = current;
        current.right = newnode;
        //current=current.right;  
    }
 
    public void display() {
        node current = head;
        do {
            System.out.print("     " + current.data);
            current = current.right;
        } while (current != head);
        System.out.println();
    }
 
    public void displayDescending() {
        node current = tail;
        int data1;
        while (current.left != null) {
            if (current.data > current.left.data) {
                data1 = current.left.data;
                current.left.data = current.data;
                current.data = data1;
                current = current.left;
            }
 
            System.out.println(current.data + "    ");
        }
        System.out.println();
    }
 
    public void displayAscending() {
        node current = head;
        int data1;
        while (current.right != null) {
            if (current.data > current.right.data) {
                data1 = current.right.data;
                current.right.data = current.data;
                current.data = data1;
                current = current.right;
            }
 
            System.out.println(current.data + "    ");
        }
        System.out.println();
    }
}
 
class Circular_Double {
 
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        Link obj = new Link();
        while (true) {
            System.out.println("*******Please select the option.*********");
            System.out.println("\t1.Insert the element at first in the list."
                    + "\n\t2.Insert at element at end."
                    + "\n\t3.Insert element at certain positon."
                    + "\n\t4.Insert element at last."
                    + "\n\t5.Delete the element."
                    + "\n\t6.Search element."
                    + "\n\t7.display the Linked list."
                    + "\n\t8.display the Linked List ordered ascending"
                    + "\n\t9.display the Linked List ordered descending"
                    + "\n\t10.Exit from the program.");
 
            int num = scan.nextInt();
            switch (num) {
                case 1:
                    System.out.println("Insert the element.");
                    int n = scan.nextInt();
                    obj.insertfront(n);
                    break;
                case 2:
                    System.out.println("Insert the element.");
                    n = scan.nextInt();
                    obj.insertend(n);
                    break;
                case 3:
                    System.out.println("Insert the element.");
                    n = scan.nextInt();
                    System.out.println("POSITION");
                    int p = scan.nextInt();
                    obj.insertatPosition(n, p);
                    break;
                case 7:
                    obj.display();
                    break;
                case 8:
                    obj.displayAscending();
                    break;
                case 9:
                    obj.displayDescending();
                    break;
                case 10:
                    System.exit(0);
                    break;
                default:
                    System.out.println("U entered invalied data.So,enter valied data.");
            }
        }
    }
}

Let's suppose I inserted the number 4 and then the number 10. If I press number 8 to order it ascending, it gets into an infinite loop printing the number 10.