// Source code example for "A Practical Introduction
// to Data Structures and Algorithm Analysis"
// by Clifford A. Shaffer, Prentice Hall, 1998.
// Copyright 1998 by Clifford A. Shaffer

class Link {  // Singly linked list node with freelist
  private Object element; // Object for this Link
  private Link next;      // Pointer to next Link in list
  Link(Object it, Link nextval)          // Constructor 1
  { element = it;  next = nextval; }     //  Given Object
  Link(Link nextval) { next = nextval; } // Constructor 2
  Link next() { return next; }
  Link setNext(Link nextval) { return next = nextval; }
  Object element() { return element; }
  Object setElement(Object it) { return element = it; }

  // Extensions to support freelists
  static Link freelist = null;     // Freelist for the class

  static Link get(Object it, Link nextval) { // Get new link
    if (freelist == null)
      return new Link(it, nextval); // Get from free store
    Link temp = freelist;           // Get from freelist
    freelist = freelist.next();
    temp.setElement(it);
    temp.setNext(nextval);
    return temp;
  }

  void release() {    // Return Link to freelist
    element = null;   // Drop reference to the element
    next = freelist;
    freelist = this;
  }
} // class Link