node.java

public class Node<T> {

    private T a;
    private Node next;

    public Node(T a) {
        this.a = a;
    }

    // 先頭に追加する
    Node add(T n) {
        return new Node(n).setNext(this);
    }

    private Node setNext(Node n) {
        this.next = n;
        return this;
    }

    int length() {
        if (next == null) {
            return 1;
        } else {
            return 1 + this.next.length();
        }
    }

    @Override
    public String toString() {
        return this.next != null
                ? this.a.toString() + "," + this.next.toString()
                : this.a.toString() + ",Nil";
    }

    public static void main(String[] args) {
        Node<Integer> n = new Node<Integer>(3).add(2).add(1);
        System.out.println(n);
        System.out.println(n.length());
    }
}