public PersonNode(String name, int age) { p = new person(name, age); next = null; prev = null; }
public PersonNode(person p) { this.p = p; next = null; prev = null; }
public PersonLinkedList(person p) { first = new PersonNode(p); }
public PersonNode() { p = new person(null, 0); prev = null; next = null; }
public person(person pre, person next, int val) { Prev = pre; Next = next; Val = val; }