How to call function of linkedkist without using test case

See more:

Java

algorithm

,i want to call the function of linkedlist in tescase funtion but using psvm and not using testcase

What I have tried:

this is the function of reverselinked list

package Linked_List;

public class ReverseALinkedList {
    static ListNode reverseWithoutExtraSpace(ListNode head) {
        if (head == null) {
            return null;


        }
        if (head.next == null) {
            return null;
        }
        ListNode preNode = null;
        ListNode currNode = head;
        while (currNode != null) {
            ListNode nextNode = currNode.next;
            currNode.next = preNode;
            preNode = currNode;
            currNode = nextNode;

        }
        head = preNode;

        return head;
    }
}`

This is the test case

package Linked_List;

import Linked_List.ListNode;
import org.junit.jupiter.api.Test;

import static Linked_List.ReverseALinkedList.reverseWithoutExtraSpace;
import static org.junit.jupiter.api.Assertions.*;

public class ReverseALinkedListTest {
    private static final ReverseALinkedList reverseALinkedList = new ReverseALinkedList();
    public ReverseALinkedListTest() {
        reverseALinkedList = new ReverseALinkedList();
        //ListNode reversedList = reverseALinkedList.reverseWithoutExtraSpace(head);
    }
   @Test
    void testReverse1() {
        ListNode head = new ListNode(4);
        head.next = new ListNode(8);
        head.next.next = new ListNode(15);
        head.next.next.next = new ListNode(16);

        ListNode reversedList = reverseALinkedList.reverseWithoutExtraSpace(head);

        assertEquals(16, reversedList.val);
        assertEquals(15, reversedList.next.val);
        assertEquals(8, reversedList.next.next.val);
        assertEquals(4, reversedList.next.next.next.val);
        assertNull(reversedList.next.next.next.next);


    }

    
    }


}