for:each bummer

[Roedy Green]

I just discovered you can't use the new for:each syntax here:

for ( Enumeration e = zip.entries(); e.hasMoreElements(); )
{
ZipEntry entry = (ZipEntry)e.nextElement();

It only works on Iterators (or more precisely that which implements
Iterable.)

I wonder why they left them out?

--
Bush crime family lost/embezzled $3 trillion from Pentagon.
Complicit Bush-friendly media keeps mum. Rumsfeld confesses on video.
http://www.infowars.com/articles/us/mckinney_grills_rumsfeld.htm

Canadian Mind Products, Roedy Green.
See http://mindprod.com/iraq.html photos of Bush's war crimes

 

[Thomas Hawtin]

I just discovered you can't use the new for:each syntax here:

for ( Enumeration e = zip.entries(); e.hasMoreElements(); )
{
ZipEntry entry = (ZipEntry)e.nextElement();

You can write that without casts:

for (
Enumeration<? extends ZipEntry> en = zip.entries();
en.hasMoreElements();
) {
ZipEntry entry = en.nextElement();

It only works on Iterators (or more precisely that which implements
Iterable.)

I wonder why they left them out?

You don't think Enumerators are a bit old for a freshly born language
feature?

As ZipFile is a class rather than an interface, they could add entrySet
or even entryMap to make it work with the enhanced for loop.

Tom Hawtin

 

[Dale King]

I just discovered you can't use the new for:each syntax here:

for ( Enumeration e = zip.entries(); e.hasMoreElements(); )
{
ZipEntry entry = (ZipEntry)e.nextElement();

It only works on Iterators (or more precisely that which implements
Iterable.)

I wonder why they left them out?

I have no problem with Enumerations not being supported in favor of
iterators, but the reason that iterators are not supported is that they
are one time use only.

Consider this code in your scheme:

Iterator<Object> iter = myCollection.iterator();

for( int i = 0: i < 10; i++ )
{
for( Object o : iter )
{
System.println( o );
}
}

Which will NOT print the contents of the collection 10 times, but only
once. I can see this might potentially confuse a newbie.

 

[Aleksi Kallio]

for ( Enumeration e = zip.entries(); e.hasMoreElements(); )

It only works on Iterators (or more precisely that which implements
Iterable.)
I wonder why they left them out?

The idea was that for(each) is a nice shorthand for the usual cases and
would not support more complicated scenarios. A very generic for(each)
iteration would have naturally been quite complicated, yet maybe not
powerful enough to cover all cases.

I think it sounds quite reasonable...

 

[Roedy Green]

The idea was that for(each) is a nice shorthand for the usual cases and
would not support more complicated scenarios. A very generic for(each)
iteration would have naturally been quite complicated, yet maybe not
powerful enough to cover all cases.

just what CAN you do with it?

--
Bush crime family lost/embezzled $3 trillion from Pentagon.
Complicit Bush-friendly media keeps mum. Rumsfeld confesses on video.
http://www.infowars.com/articles/us/mckinney_grills_rumsfeld.htm

Canadian Mind Products, Roedy Green.
See http://mindprod.com/iraq.html photos of Bush's war crimes

 

[Tor Iver Wilhelmsen]

just what CAN you do with it?

Loop over arrays and collections. Which is what you used
iterator()/elements() for earlier. The "for each" statement will get
the iterator for you.