Java Stack Illegal start Operation

[messynaddy]

public class Stack extends LinkList{

public Stack(){

    public void push (Object element)
    {
        insertAtFront (element);
    }

    public Object pop(){
        return removeFromFront();
    }

    public Object peek(){
        return getFirst();
    }
}

Im trying to create a movieApp using pop push and peek method(Stack). But once the class got compiled, it shows a message "illegal start operation" regarding public void push (Object element). Here is my full coding for class Stack

[JamesCherrill]

That doesn't look like the standard Java LinkedList. Is that a class you wrote/were given? If so, we'll need the code for that too.

[messynaddy]

Yep. And the LinkList codes :

public class LinkList
{
    private Node first;
    private Node last;
    private Node current;

    public LinkList()
    {
        first = null;
        last = null;
        current = null;
    }

    public boolean isEmpty()
    {
        return (first==null);
    }

    public void insertAtFront(Object insertItem)
    {
        Node newNode = new Node(insertItem);

        if (isEmpty())
        {   first = newNode;
            last = newNode;
        }
        else
        {
            newNode.next = first;
            first = newNode;
        }
    }

    public void insertAtBack(Object insertItem)
    {
        Node newNode = new Node(insertItem);

        if (isEmpty())
        {   first = newNode;
            last = newNode;
        }
        else
        {
            last.next = newNode;
            last = newNode;
        }
    }

    public Object removeFromFront()
    {   
        Object removeItem = null;
        if (isEmpty())
        {   
            return removeItem;
        }
        removeItem = first.data;
        if ( first == last)
        {   
            first = null;
            last = null;
        }
        else
            first = first.next;
        return removeItem;
    }

    public Object removeFromBack()
    {   
        Object removeItem = null;
        if (isEmpty())
        {   
            return removeItem;
        }
        removeItem = last.data;
        if ( first == last)
        {   
            first = null;
            last = null;
        }
        else
        {
            current = first;
            while (current.next != last)
                current = current.next;
            last = current;
            last.next = null;
        }         
        return removeItem;
    }

    public Object getFirst()
    {   
        if (isEmpty())
            return null;
        else
        {   
            current = first;
            return current.data;
        }
    }

    public Object getNext()
    {   
        if (current == last)
            return null;
        else
        {
            current = current.next;
            return current.data;
        }               
    }
}

[JamesCherrill]

... also, you can't define a method inside another method - you try to define push inside the constructor (that would have been more obvious had you posted the exact complete error message rather than your own summary of it)

[messynaddy]

This is my App :

import javax.swing.*;

public class MovieVCDApp{

    public static void main(String [] args){

        Stack tS = new Stack();

        for(int x=0; x<2; x++)
        {
            String title = JOptionPane.showInputDialog("Movie Tile:");
            String language = JOptionPane.showInputDialog("Language:");
            double price = Double.parseDouble(JOptionPane.showInputDialog("Price :"));
            int duration = Integer.parseInt(JOptionPane.showInputDialog("Time Duration :"));

            MovieVCD movie= new MovieVCD(title,language,price,duration);
            tS.push(movie);


        }

        String lui= "VCD in Bahasa:" ;
        int count = 0;
        Movie m1=null;

        while(!tS.isEmpty()){
        {

            m1=(Movie)tS.pop();
            if(m1.getLanguage().equalsIgnoreCase("Melayu")){
            {
                String out = "\n" + m1.getTitle() + "\t" + m1.getPrice() + "\t" + m1.getDuration();
                count++;

                System.out.println(temp.toString());
            }
            tempStack=push(m1);


        if(count>0)
        {   
            System.out.println("\n" + out);
        }    
        else 
        {    System.out.println("No movies found");
        }   
    }
        int kira=0;
        while(!tS.isEmpty())

        {
            m1=(Movie)tempStack.pop();
            if (m1.getPrice>15)
            {
               kira++ ;
               tS.push(m1);
            }
            System.out.println("VCDs that costs more than RM15 is about" + kira + "VCDs") ;
            System.out.println("\nTitle :"  + m1.getTitle) ;
        }   
            double sum=0.0;

        for(int k=0;k<2;k++)
        {
            sum=sum+m1[k].getPrice();
        }

        //average price

        double average=sum/2;
        {
        System.out.println("Average price for all DVDs are:" +average);
        }
    }
}
}
}

[JamesCherrill]

Assuming that by now you're fixed the original code problem...
Your LinkedList and Stack classes should be updated to support generics so youy can code something like
Stack<Movie> tS = new Stack<Movie>();
which will save you a load of uneccessary casts, and maybe some bugs.
... but if your course hasn't covereed that yet, just set this post aside for later.

[messynaddy]

I am not usulally using generics but thanks i'll try to apply it to my codes. Btw does generics could be imply on LinkList too?

[Traps]

Yes, your LinkedList class will greatly benefit from using generics.

[JamesCherrill]

does generics could be imply on LinkList too?

Yes, absolutely.
ps: You may be able to speed up the learning process by having a quick look at Java's own LinkedList implementation and how that uses generics.

[messynaddy]

Thank u so much for ur feedback! I like object oriented but it involve with too many methods.. Gotta deal with it. Anyway thanks again :)