The Practice-IT implementation of a LinkedList

LinkedIntList.java

public class LinkedIntList {
    
    private ListNode front;
    
    public LinkedIntList() {
         front = null;
    }
    
    public int size() {
        int count = 0;
        ListNode current = front;
        while(current != null) {
          current = current.next;
          count++;
        }
        return count;
    }

    public int get(int index) {
        return nodeAt(index).data;
    }
    
    public String toString() {
        if(front == null) {
            return "[]";
        } else {
            String result = "[" + front.data;
            ListNode current = front.next;
            while(current != null) {
                result += ", " + current.data;
                current = current.next;
            }
            result += "]";
            return result;
        }
    }
    
    public int indexOf(int value) {
      int index = 0;
      ListNode current = front;
      while(current != null) {
          if(current.data == value) {
              return index;
          }
          index++;
          current = current.next;
      }
      return -1;
    }
    
    
    public void add(int value) {
        if(front == null) {
            front = new ListNode(value);
        } else {
              ListNode current = front;
              while( current.next != null) {
                  current = current.next;
              }
              current.next = new ListNode(value);
        }
    }
    
    public void add(int index, int value) {
        if(index == 0) {
             front = new ListNode(value, front);
        } else {
             ListNode current = nodeAt(index-1);
             current.next = new ListNode(value, current.next);
        }
    }
    
    public void remove(int index) {
         if(index == 0) {
               front = front.next;
         } else {
             ListNode current = nodeAt(index-1);
             current.next = current.next.next;
         }
    }
    
    private ListNode nodeAt(int index) {
          ListNode current = front;
          for(int i=0; i<index; i++) {
              current = current.next;
          }
          return current;
    }
}

ListNode.java

public class ListNode {
    public int data;
    public ListNode next;

    public ListNode() {
         this(0,null);
    }

    public ListNode(int data) {
         this(data,null);
    }

    public ListNode(int data, ListNode next) {
         this.data = data;
         this.next = next;
    }
}