Effiency in dropout stack program

Question

Does anyone think this code is efficient?
Thanks
import java.util.*;
  public class dropOutStack<E> {     
     //stack size limit      
      public final int stackLimit = 5;
      private static class LinkStack <E>  {
             private E data;
              private LinkStack<E> next = null;
          private LinkStack<E> prev = null;
              private LinkStack(E dataItem) {
                 data = dataItem;  ;
           // Stack Items
                 LinkStack<String> item1 = new LinkStack<String>("Red");
           LinkStack<String> item2 = new LinkStack<String> ("Yellow");
           LinkStack<String> item3 = new LinkStack<String>("Green");
           LinkStack<String> item4 = new LinkStack<String>("Blue");
           LinkStack<String> item5 = new LinkStack<String>("Orange");
              LinkStack<String> item6 = new LinkStack<String>("Silver");
     public void print() {
          //links
           item1.next = item2;
           item1.prev = null;
           item2.next = item3;
           item2.prev = item1;
           item3.next = item4;
           item3.prev = item2;
           item4.next = item5;
           item4.prev = item3;
           item5.next = null;
           item5.prev = item4;
           LinkStack<String> obj = item1;
           LinkStack<String> empty = null;
           while (obj != empty) {
                     System.out.print(obj.data + " ");
               obj = obj.next;     
       public void  push() {
          LinkStack<String> newitem2 = item1;
          LinkStack<String> newitem3 = item2;
          LinkStack<String> newitem4 = item3;
          LinkStack<String> newitem5 = item4;
               item2 = newitem2;
          item3 = newitem3;
          item4 = newitem4;
          item5 = newitem5;
          item1.next = item1.next.next;
          item1 = item6;
     //Test method   
      public static void main(String [] args) {
           dropOutStack<String> itemStack = new dropOutStack<String>();
           itemStack.print();
           //push Silver onto the LinkStack
             itemStack.push();
           System.out.println("\nStack after drop out: ");
           itemStack.print();
}

Answer 1

No, because:
1) you can't change the size of the stack without changing the code
2) when you push something, you reassign a whole bunch of variables to each other unnecessarily
3) You're hardcoding the contents of the stack into the program (write an external test class instead, or put the test code into the main method, preferably the former)
4) There is no pop, and you're popping stuff (?) in print(). Shouldn't print have no side effects? Have you combined pop and print for some reason?
5) Push doesn't take an argument, so it's not really a push method. And it seems to eliminate item one while also rotating item 6 to the beginning, maybe?
6) No constructor? The only place where you actually create the linking of the linked list, is in your print method?
Look: the advantage of linked lists is that things like inserting at the beginning or end can take constant time (you only have to futz with a single element or maybe two elements for a drop-out stack). That's why they're ideal for things like stacks.
So you shouldn't have any methods that touch every single item in the stack. If you want to do that you're on the wrong track.
Here's a hint: the DropOutStack class should have 4 fields:
1) the maximum size of the stack (as given in the constructor)
2) the current size
3) a reference to the first element (where you drop things from)
4) a reference to the last element (where you push/pop things to)
In addition you'll need a constructor that takes a maximum size, a pop method that takes no argument and returns a value, a push method that takes a value and returns nothing, an isEmpty method that takes no argument and returns a boolean, and possibly a size method that takes no argument and returns an int (the current size). Optionally you can have a print method that takes no argument, returns nothing, but prints the contents of the stack to standard output as a side-effect.
Look in your textbook if you don't understand any of this.
Write a skeleton class that has that stuff but has empty method bodies. Then fill in the method bodies. It may be easier to understand that way.