Singly linked list implementation in Java

SinglyLinkedList.java

    public class ListNode {
        //has two pieces: data and pointer to next node
        private int value;
        private ListNode next;
        
        //constructors
        
        public ListNode() {
        }
        
        public ListNode(int value) {
            this.value = value;
        }
        
        public ListNode(int value, ListNode next) {
            this.value = value;
            this.next = next;
        }
        
        //since data and next are private, we have to have getters and setters
        
        public int getValue() {
            return this.value;
        }
        
        public void setValue(int value) {
            this.value = value;
        }
        
        public ListNode getNext() {
            return this.next;
        }
        
        public void setNext(ListNode next) {
            this.next = next;
        }
    }
    
    //now that we have the list node, we need to construct the list
    //the list should have a root, a current size, and a maximum size
    //we should be able to set the root of the list and get the current/max sizes
    //we should be able to insert after a certain node as well as at the beginning
    //we should be able to remove both the nth node as well as a value in the list
    
    private ListNode root;
    private int number;
    private int maximum = 15;
    
    public class List {
        public void setRoot(ListNode root) {
            root.next = this.root;
            this.root = root;
        }
        
        public int getSize() {
            return this.number;
        }
        
        public int getMax() {
            return this.maximum;
        }
        
        public void insert_at_end(int value) {
            ListNode tmp = this.root;
            ListNode tmp2 = new ListNode(value);
            
            //check for size
            
            if (this.number == this.maximum) {
                return "The list is full."
            }
            //check for empty list
            if (this.root == null) {
                this.root = tmp2;
            }
            //keep getting next until you hit the end, then add the node
            while (tmp.getNext() != null) {
                tmp = tmp.getNext();
            }
            
            tmp.setNext(tmp);
            this.number++;
        }
        
        public void insert_at_nth(int n, int value) {
            int count = 0;
            ListNode tmp2 = new ListNode(value);
            ListNode tmp = this.root;
            
            //again, check for size and empty list
            
            if (this.number == this.maximum) {
                return "The list is full."
            }
            
             if (this.root == null) {
                this.root = tmp2;
            }
            
            while (count < n) {
                tmp = tmp.getNext();
                count++;
            }
            //tmp is now the nth node
            //new node's next is the old next
            tmp2.setNext(tmp.getNext());
            //point old node's next to new node
            tmp.setNext(tmp2);
            this.number++;
        }
        
        public void remove_nth(unsigned int n) {
            ListNode tmp = this.root;
            //check for empty list
            if (this.root == null) {
                return;
            }
            //if asking to remove 0th node, make the next NODE the root
            if (n == 0) {
                this.root = this.root.getNext();
            }
            //navigate to (n-1)th node
            for (int i = 0; i < n-1; i++) {
                tmp = tmp.getNext();
            }
            tmp.setNext(tmp.getNext().getNext());
            this.number--;
        }
        
        public void remove_value(int value) {
            ListNode tmp = this.root;
            if(this.root == null) {
                return;
            }
            
            if(tmp.value == value) {
                this.root = this.root.getNext();
            }
            
            while(tmp.getNext().getValue() != value) {
                tmp = tmp.getNext();
                if(tmp.getNext() == null) {
                    return;
                }
                
            }
            tmp.setNext(tmp.getNext().getNext());
        }
    }