Hi - I have written the following c

[Knackers]

Hi - I have written the following class which impliments a Stack:

//ImageStack.java

import java.io.*;
import java.util.*;


class ImageStack implements IsaStack {

private Vector myStack;

public ImageStack(){
myStack = new Vector();
}

public void push(Object o){
myStack.add(o);
}

public Object pop(){
return (myStack.remove(myStack.size()-1));
}

public Object peek(){
return (myStack.get(myStack.size()-1));
}

public static void main(String args[]){

System.out.println("Test Stack"
ImageStack stk = new ImageStack() ;
stk.push(new Integer(1));
stk.push(new Integer(4));
System.out.println(stk.peek());


}
}

-----------------------------------
//IsaStack.java

public interface IsaStack{
public void push(Object o);
public Object pop();
public Object peek();
}

-----------------------------------

I understand that a Stack (like a Vector ) can only accept an Object, and thus primitives must be cast as objects using their wrapper classes. However, my question for the day is: How can I modify this class so that the ImageStack so that it becomes a stack for storing objects of type Image only.

Also, how would one clear the stack? I would imagine that one way to do it would be to implement the stack as inheriting from Vector, then you could use the removeAllElements()?

I know this is probably fairly elementary but I am pretty new to OO concepts.

Cheers

 

[tiagosilva]

Hi,

public void push(Image o){
myStack.add((Image) o);
}

Tiago

Regards,
Tiago

 

[Knackers]

Thanks for your quick reply Tiago.

I have changed my push() method as you suggest, but the compiler throws this error:

--------------------------------------------

C:\Ben\University\cosc1295\lab4>javac ImageStack.java
ImageStack.java:15: cannot resolve symbol
symbol : class Image
location: class ImageStack
public void push(Image o){
^
ImageStack.java:16: cannot resolve symbol
symbol : class Image
location: class ImageStack
myStack.add((Image) o);
^
2 errors

--------------------------------------------

I assume that this is because it does not as yet know what an Image object is? If so, then do I have to declare / create one at the top of my ImageStack class? DO I need to write and Image Class?

Cheers

 

[tiagosilva]

Hi,

Yes, you may need to write Image class. I don't know exactly what's the purpose of your class, and if you can use some class that already exists.

Tiago

Regards,
Tiago

 

[Knackers]

Cheers Tiago

There is no real purpose to my ImageStack class - it is mainly an exercise to demonstrate wrapper classes. SO I guess I need to make a wrapper for my Images so that they are just passed to the Stack as any other Object would be.