Question

• Change the LinkList class to work with DNode, in particular, adapt the implementation of the void LinkList.deleteLast() method.

LINKLIST CLASS BELOW

/**
* Builds a singly linked list of size 5 and prints it to the console.
*
* @author Jochen Lang
*/

class LinkList {
DNode llist;

LinkList( int sz ) {
   if ( sz <= 0 ) {
   llist = null;
   }
   else {
   // start with list of size 1
   llist = new DNode( "0", null, null );
   DNode current = llist; // temp node for loop
   // add further nodes
   for ( int i=1; i        // create node and attach it to the list
       DNode node2Add = new DNode( Integer.toString(i), null, null );
       current.setNext(node2Add); // add first node
       current=node2Add;
   }
   }
}
  
/**
* Print all the elements of the list assuming that they are Strings
*/
public void print() {
   /* Print the list */
   DNode current = llist; // point to the first node
   while (current != null) {
   System.out.print((String)current.getElement() + " ");  
   current = current.getNext(); // move to the next
   }
   System.out.println();  
}

public void deleteFirst() {
   if ( llist != null ) {
   llist = llist.getNext();
   }
}

public void deleteLast() {

}

// create and display a linked list
public static void main(String [] args){
   /* Create the list */
   LinkList llist = new LinkList( 5 );
   /* Print the list */
   llist.print();
   /* delete first and print */
   llist.deleteFirst();
   llist.print();
   /* delete last and print 5 times */
   for ( int i=0; i< 5; ++i ) {
   llist.deleteLast();
   llist.print();
   }
}
}

DNODE CLASS BELOW

public class DNode {
  private Object element;
  private Node next;
  private Node prev;
  Node() { this(null, null, null); }
    Node(Object e, Node n, Node p) {
    element = e;
    next = n;
    prev = p;
  }
  public void setElement(Object newElem) { element = newElem; }
  public void setPrev(Node newPrev) { prev = newPrev; }
  public void setNext(Node newNext) { next = newNext; }
  public Object getElement() { return element; }
  public Node getNext() { return next; }
  public Node getPrev() { return prev; }
}

Answer 1

Working fine now with DNode

/**

* Builds a singly linked list of size 5 and prints it to the console.

*

* @author Jochen Lang

*/

public class LinkList {

DNode llist;

LinkList(int sz) {

if (sz <= 0) {

llist = null;

} else {

// start with list of size 1

llist = new DNode("0", null, null);

DNode current = llist; // temp node for loop

// add further nodes

for (int i = 1; i <= 5; ++i) { // create node and attach it to the list

DNode node2Add = new DNode(Integer.toString(i), null, null);

current.setNext(node2Add); // add first node

current = node2Add;

}

}

}

/**

* Print all the elements of the list assuming that they are Strings

*/

public void print() {

/* Print the list */

DNode current = llist; // point to the first node

while (current != null) {

System.out.print((String) current.getElement() + " ");

current = current.getNext(); // move to the next

}

System.out.println();

}

public void deleteFirst() {

if (llist != null) {

llist = llist.getNext();

}

}

public void deleteLast() {

if (llist == null)

return;

else {

DNode temp = llist;

while (temp.getNext().getNext() != null)

temp = temp.getNext();

temp.setNext(null);

}

}

// create and display a linked list

public static void main(String[] args) {

/* Create the list */

LinkList llist = new LinkList(5);

/* Print the list */

llist.print();

/* delete first and print */

llist.deleteFirst();

llist.print();

/* delete last and print 5 times */

for (int i = 0; i < 5; ++i) {

llist.deleteLast();

llist.print();

}

}

}

===============================================================================
// DNODE CLASS BELOW, Modified DNODE Class as well

public class DNode {

private Object element;

private DNode next;

private DNode prev;

DNode() {

this(null, null, null);

}

DNode(Object e, DNode n, DNode p) {

element = e;

next = n;

prev = p;

}

public void setElement(Object newElem) {

element = newElem;

}

public void setPrev(DNode newPrev) {

prev = newPrev;

}

public void setNext(DNode newNext) {

next = newNext;

}

public Object getElement() {

return element;

}

public DNode getNext() {

return next;

}

public DNode getPrev() {

return prev;

}

}

======================================================================

Thanks, PLEASE COMMENT if there is any concern.