/** * Java code sample  */  interface Stack {  void push (Object);  Object pop ();  Object top (); }  /* DoubleLinkedList */ class DList {  public void insert (DNode pos, Object o) {... }  public void remove (DNode pos, Object o) {... }    public void insertHead (Object o) {... }  public void insertTail (Object o) {... }    public Object removeHead () {... }  public Object removeTail () {... }    public Object getHead () {... }  public Object getTail () {... } }  /* Adapt DList class to Stack interface */ class DListImpStack extends DList implements Stack {  public void push (Object o) { insertTail (o);  }    public Object pop () { return removeTail ();  }    public Object top () { return getTail ();  } }