syntax question

[kwame Iwegbue]

in tutorial on Collections from java.sun:

The following method shows you how to use an iterator to filter an arbitrary Collection (that is, traverse the collection removing specific elements):

 
 
static void filter(Collection c) {
    for (Iterator i = c.iterator(); i.hasNext(); ) 
        if ([B]!cond[/B](i.next())) 
            i.remove();
}
 

please what does "!cond" mean?

[ November 11, 2005: Message edited by: kwame Iwegbue ]
[ November 11, 2005: Message edited by: kwame Iwegbue ]

[Jody Brown]

I would assume it is just some arbitary condition that, if is not true (the "!" part beforehand), then the instance is removed from the collection. The condition could be anything - a !=7, xyz!=12345.

[Stan James]

 if (!cond(i.next())) 

Work from the inside out here.

i.next() gets the next value from the iterator.

cond( i.next() ) calls a method called "cond" passing that value as a parameter. cond() apparently returns a boolean.

!cond turns into the opposite boolean value. If cond returns true, the if test fails. If cond returns false, the if test passes.

Does that help?

[kwame Iwegbue]

helps a whole bunch. Thanks once again guys. Always get confused by nested statements; also by "!"

[ November 11, 2005: Message edited by: kwame Iwegbue ]

why could'nt it just be-

 static void filter(Collection c) {
    for (Iterator i = c.iterator(); i.hasNext(); )  
            i.remove();
} 

[ November 11, 2005: Message edited by: kwame Iwegbue ]
[ November 11, 2005: Message edited by: kwame Iwegbue ]

[Jaime M. Tovar]

Cause this way the for loop will remove every object in the collection, the cond function lets you specify the condition that the object must not fulfill in order to be removed. Lets say its your filter, only the objects that fail the condition will be removed