class MyStack {

    // This is now an array of Object's.
    Object[] stack;

    int stackTop;
    

    public void initialize ()
    {
        stack = new Object [100];
    }
    

    // Note: the parameter is now of type Object:

    public void push (Object value)
    {
        // A shorter version of push using the pre-increment operator.
        stack[++stackTop] = value;
    }
    

    // Note: the return value is now of type Object:

    public Object pop ()
    {
        Object value = stack[stackTop];
        stackTop --;
        return value;
    }
    
    public boolean isEmpty ()
    {
        if (stackTop < 0) {
            return true;
        }
        else {
            return false;
        }
    }

}


public class StackExample3 {

    public static void main (String[] argv) 
    {
        MyStack stack = new MyStack ();

        stack.initialize ();
        
        // Dump strings on stack. A String is an Object, so
        // it's OK to put strings.
        stack.push ("Alice");
        stack.push ("Bob");
        stack.push ("Chen");
        
        while (! stack.isEmpty ()) {
            // Notice the cast required from Object to String.
            String name = (String) stack.pop ();
            System.out.println ("Removed " + name);
        }
        
    }
    

}