Call methods of objects stored in a vector !

[Tom Roffe]

hello all,

it's been a while since i posted last, and i would like to thank any reading or answering this post. as i know your time is valuable.

i currently having problems with one specific part of my appliction. i have a vector which is storing objects of a class i have created (OrderItem). i can add/remove objects into/from the vector fine. i can use the Enumeration interface to go though the items and using a while loop and call the toString method of each object in the vector. but i would like to call a method within the object called saveOrderItem(). when i try to complie the code i get "can't resolve symbol saveOrderItem() from location class java.lang.Object" i don't understand, whats going on. i made OrderItem extend Object (a sujjestion)and still nothing(altough i didn't think it would). please help my coursework depends onit.

public void saveOrder() {

if (orderVector.isEmpty())
{
System.out.println("You Have Not Ordered Anything.");
}
else
{
Enumeration items = orderVector.elements();
while (items.hasMoreElements())
{
items.nextElement().saveOrderItem();

// saveOrderItem() is method of OrderItem
// many OrderItems in vector.
}
}

}

if you need to see any other code please say....


thanks

Tom R

[Jase Jones]

complete guess, but maybe if you cast it.

[Ernest Friedman-Hill]

Whoever told you to make OrderItem extend Object apparently isn't aware that any class that doesn't explicitly extend another class implicitly extends Object, so adding "extends Object" accomplishes exactly nothing.

The correct answer: the compiler doesn't know that the objects in the Vector are OrderItems. You have to tell it by using a "typecast"; it will then let you treat the object as an OrderItem. A typecast (or "cast" for short) is simply the name of the real class of the object in parentheses:

OrderItem item = (OrderItem) items.nextElement();
item.saveOrderItem();

You can do this all in one step by using some extra parentheses:

((OrderItem) items.nextElement()).saveOrderItem();

[Tom Roffe]

Thanks, worked a treat. I did think that extending object would be a dead end as you said for that reason. But the person that (mis-)advised was adamant that it was needed.

Thanks again

Tom R