Thread: Stack

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JOptionPane;
import java.util.*;
import java.io.*;
//Paul Adcock
// Assignment 4
// Lasted Worked On: 10/12/2010
 
// this class is the Doubly Linked list class.  It has a Node that holds a reference to some date of type T and has a reference
// to the next Node and to the previous Node.  
 
 
public class DoublyLinkedList<T>
{
    private class Node<T>
    {
        private T data;
        private Node<T> next;
               private Node<T> previous;
 
        public Node(T data,Node<T> next, Node<T> previous)
        {
            this.data = data;
            this.next = next;
                       this.previous=previous;
        }
 
        public T getData()
        {
            return data;
        }
 
        public Node<T> getNext()
        {
            return next;
        }
 
public Node<T> getPrevious()
{
return previous;
}
 
        public void setNext(Node<T> next)
        {
            this.next = next;
        }      
 
public void setPrevious(Node<T> previous)
{
this.previous = previous;
}
    }
 
    private Node<T> head;//head of the linked list
       private Node<T> tail; // tail of linked list
    private int size;
   private ImageIcon icon;
   private Icon icon2;
    public DoublyLinkedList()
    {
        head = null;
                tail = null;
        size = 0;
        icon = new ImageIcon("doh3.jpg");
    }
 
    // returns a String of all the items in the linked list.  
    public String toString()
    {
        String str = "[";
 
        Node<T> curr;
 
        for (curr=head;curr!=null;curr = curr.getNext())
        {
            str = str + curr.getData();
            if (curr.getNext()!=null)
                str = str + " ";
        }
        str = str + "]";
        return str;
 
 
    }
 
public void removeRange(int from, int to)
{
if (from < 0 || from > = Size() || to < 0 || to >=Size())
{
return;
}
 
for (int i = from; i <=to; i++)
{
remove(i);
}
}
 
    // adds the data as the first element.  If the list size is 0, makes first element tail.  If head is not null, it puts the old
    // tail as the second element and the new element as the new head.  
    public void addFirst(T data)
{  
    /*  Since this is the first Object,  previous should be null
     */
    Node<T> newNode = new Node<T>(data,head,null);
    //We know that if head is null, the list is empty
    if (head==null)
        {
        //If the list is empty,  tail will be newNode
        tail = newNode;
    }
 
    if(head!=null)
        head.setPrevious(newNode);
 
    //We want to set head to be newNode
// if the list was empty before, both head and tail will be set to newNode;
    head = newNode;
    //Increment Size
    size++;
}
 
    public void removeFirst()
    {
           if (size == 0)
{
               JOptionPane pane = new JOptionPane();
               pane.setIcon(icon);
pane.showMessageDialog(null, "Cannot remove from an empty list!", "Invalid removal", JOptionPane.ERROR_MESSAGE);
pane.setMessageType(JOptionPane.ERROR_MESSAGE);
 
return;
}
        Node<T> current = head; // creates a Node called current and sets it to head.
 
        head = head.getNext(); //move head to the next element
 
        current.setNext(null);
size--;
    }
 
    public void addLast(T data)
    {
        //If there are no elements, use the addFirst method
        if (tail == null)
        {
            addFirst(data);
            return;
        }
        /* Create the new Node from the data. Set next to null
         * because this will be the last element and will not
         * have a next. Set previous to tail because tail has
         * not been changed yet and is currently referencing
         * that element that will be directly before this element
         */
        Node<T> newNode = new Node(data,null,tail);
        /* Since the tail variable still references the element
         * directly before the new element, we can set that node's
         * next to our new element.
         */
        tail.setNext(newNode);
        //Set tail to our new Node
        tail = newNode;
        //Increment size
        size++;
    }
 
    public int Size()
    {
        return(size);
    }
 
    public void add(int index,T data)
    {
        int i;
       if (index == 0)
       {
           addFirst(data);
           return;
 
       }
        if (index>size)
        {
            JOptionPane.showMessageDialog(null, "Cannot add out of bounds!", "Invalid command", JOptionPane.ERROR_MESSAGE);
            return;
        }
 
 
        if (index < 0)
        {
            JOptionPane.showMessageDialog(null, "Cannot add out of bounds!", "Invalid command", JOptionPane.ERROR_MESSAGE);
            return;
        }
 
        if (head==null)
        {
            addFirst(data);
            return;
        }
 
        if (index == size)
        {
            addLast(data);
            return;
        }
 
        //step 1
        Node<T> current;
 
        current = head;
 
        for (i=0;i<index-1;i++)
        {
            current = current.getNext();
        }
 
        //current now refers to object immediately before new node
 
        //step 2
        Node<T> newnode = new Node<T>(data,current.getNext(), current.getPrevious());
 
        //step 3
 
        current.setNext(newnode);
 
 
        size++;
    }  
 
    public void remove(int index)
    {
        if ((index<0) || (index>=size))
{
JOptionPane.showMessageDialog(null, "You cannot remove an out-of-bounds value!", "Invalid removal", JOptionPane.ERROR_MESSAGE);
            return;
        }
 
 
 
Node <T> next2, previous3;
       Node<T> NodeToRemove = head; // sets Node to remove originally to head
 
 
for (int v = 0; v < index; v++)
{
NodeToRemove = NodeToRemove.getNext(); // traverse to Node we want to remove
}
 
previous3 = NodeToRemove.getPrevious(); // sets previous3 to value before Node to remove
next2 = NodeToRemove.getNext(); // sets next2 to value after Node to remove
 
if (previous3 == null)
{
if (next2 == null)
{
head = null;
tail = null;
}
 
else
{
head = next2;
}
}
 
else
{
previous3.setNext(next2);
}
 
if (next2 == null)
{
if (previous3 == null)
{
head = null;
tail = null;
}
 
else
{
tail = previous3;
}
}
else
{
next2.setPrevious(previous3);
}
 
 
        size--;
    }
 
    public T get(int i)
    {
        if (i < 0 || i >= size)
            return null;
 
        if (i ==0)
        {
                Node<T> thisNode = head;
                return(head.getData());
        }
 
        if (i == size - 1)
        {
            Node<T> thisNode = tail;
            return(tail.getData());
        }
        Node<T> specialNode = head;
        for (int x = 1; x < i + 1; x++)
        {
            specialNode = specialNode.getNext();
        }
        return(specialNode.getData());
 
        // How do I get it to return the data at i?
 
 
    }
 
    // calls get method of first index
    public T front()
    {
        if (head == null)
            return null;
 
        return(get(0));
    }
 
    // calls get Method of last index
    public T back()
    {
        if (tail == null)
            return null;
 
        return(get(size - 1));
    }
 
    public void removeLast()
    {
 
        if (head == null)
        {
            JOptionPane.showMessageDialog(null, "Cannot remove from an empty list!", "Invalid removal", JOptionPane.ERROR_MESSAGE);
            return;
        }
        remove(Size() -1 );
    }
 
    // gets a String for the first bracket.  Then stores each set of first and last, 2nd and 2nd to last, etc, in a String array;
    // it then sets the third string to the concatination of all of the Strings in the array.  It thens puts these together and adds
    // the last set of brackets and returns the final string.  
public String printAlternate()
{
/*
This method returns a string that has
the data in the following fashion (assume for this example that the list stores String objects)
If the list is currently [amit is now here], it will return a string �[amit here is now]�
If the list is currently [amit is now currently here], it will return a string �[amit here is currently now]�
*/
    String str = "[";
    String [] str2 = new String[size];
for (int v = 0; v < size; v++)
{
    str2[v] = this.get(v) + " " + this.get(size - (v+1) );
}
String str3 = "";
for (int x = 0; x < size - 2; x++)
{
    str3 = str2[x].concat(str2[x+1]);
}
String str4 = str + " " + str3 + " " + "]";
return(str4);
}
}

import java.util.*;
import java.io.*;
 
public class MyQueue<T>
{ // beginning of class
 
private DoublyLinkedList<T> dLL;
 
public MyQueue()
{ // beginning of constructor
dLL = new DoublyLinkedList<T>();
} // end of constructor
 
public void push(T data)
{ // beginning of method
dLL.addLast(data);
} // end of method
 
public void pop()
{ // beginning of method
dLL.remove(0);
} // end of method
 
public T front()
{ // beginning of method
return dLL.get(0);
} // end of method
 
public T back()
{ // beginning of method
return dLL.get(dLL.Size() -1)
} // end of method
 
public boolean empty()
{ // beginning of method
 
if (dLL.Size() == 0)
return true;
else
return false;
} // end of method
 
public int Size()
{ // beginning of method
return dLL.Size();
} // end of method
 
} // end of class

import java.util.*;
import java.io.*;
 
public class MyStack <T>
{ // beginning of class
 
private DoublyLinkedList<T> dLL;
 
public MyStack()
{ // beginning of constructor
dLL = new DoublyLinkedList<T>();
} // end of constructor
 
public void pop
{ // beginning of method
dLL.remove(0);
 
} // end of method
 
public void push(T data)
{ // beginning of method
 
dLL.addFirst(data);
} // end of method
 
 
public T top()
{ // beginning of method
return dLL.get(0);
} // end of method
 
public int Size()
{ // beginning of method
return dLL.Size();
} // end of method
 
} // end of class

Also, you do realize that Integer has a method called compareTo(Object obj) that will let you compare Integers to see which one is greater. You'll need to make the two Stacks parallel so that when you reorganize the int values, the corresponding String values are also changed so it will print out on the same lines and not for the wrong people.

compareTo(Object obj)

return a 0 if they are equal

return a -1 if less than

return a 1 if greater than

However, as I said, unlike my DoublyLinkedList, the MyStack only knows what's in the front and the size and if the stack is empty.

Are you sure you're supposed to be using a stack to do this?