1.5 style "for" loops

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Chanchal - 28 Nov 2005 05:51 GMT

hey,

can some one tell me what is the advantage of "for each" style loop in
1.5 over the conventional for loop
thanx

chanchal

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Adam Maass - 28 Nov 2005 06:02 GMT

> hey,
>
[quoted text clipped - 3 lines]
>
> chanchal

It's a briefer syntax:

Old style:

for(Iterator i = collection.iterator(); i.hasNext(); ;) {
Item item = (Item)i.next();
...
}

New style:

for(Item item: collection) {
...
}

IMHO, the new style is conceptually a bit cleaner as well: you're applying
the body of the loop to each item in the collection in turn. You don't have
to write code for the mechanics of getting that to happen.

-- Adam Maass

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Thomas Hawtin - 28 Nov 2005 13:01 GMT

>>can some one tell me what is the advantage of "for each" style loop in
>>1.5 over the conventional for loop

> It's a briefer syntax:

And more consistent between array and non-RandomAccess Iterables.

> Old style:
>
> for(Iterator i = collection.iterator(); i.hasNext(); ;) {
> Item item = (Item)i.next();
> ...
> }

Which does conceptually the same thing as the completely different code:

final int num = array.length;
for (int ct=0; ct<num; ++ct) {
Item item = array[ct];
...
}

The new syntax does fall down if you want to remove items from an
iterator, replace items or use the index. But, say, 80% of the time it
just reads better.

Tom Hawtin

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Thomas Fritsch - 28 Nov 2005 11:04 GMT

> can some one tell me what is the advantage of "for each" style loop in
> 1.5 over the conventional for loop

Quoted from
<http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html#forloop> :
"...eliminates the drudgery and error-proneness of iterators and index
variables when iterating over collections and arrays"

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Roedy Green - 28 Nov 2005 17:14 GMT

>can some one tell me what is the advantage of "for each" style loop in
>1.5 over the conventional for loop

they both generate the same code. The for:each is terser and hence
easier to maintain and read.

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Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

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Benji - 28 Nov 2005 17:17 GMT

>>can some one tell me what is the advantage of "for each" style loop in
>>1.5 over the conventional for loop

> they both generate the same code.

That's not necessarily true. Using a for:each gives the compiler more of
a chance to optimize the loop than it would with a standard for. (Of
course, whether or not it is optimized in the current compiler/VM is
another story)

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Of making better designs there is no end,
and much refactoring wearies the body.

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1.5 style "for" loops

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