Java: "Anonymous" array in for-each-loop

Question

While I was trying something special in for loop I recognized that Java doesn't seem to like putting an anonymous array right as the source for a for-each-loop:

for (String crt : {"a","b","c"} ) {
    doSomething();
}

actually doesn't work while

String[] arr = {"a","b","c"};
for (String crt : arr ) {
    doSomething();
}

does.

Even casting the array to String[] doesn't help. When moving the cursor over the first version, eclipse tells me:

Type mismatch: cannot convert from String[] to String while meaning "crt".

Is this a bug?

I don't actually claim to have found a bug. I just ask whether it could be a bug. And it's strange that in one part this type of expression works and in another it doesn't. Not very consistent in my eyes. — Atmocreations
– Atmocreations, Commented Mar 1, 2010 at 20:48
for the record, @JoachimSauer was referring to the section Don't rush to claim that you have found a bug. the up-to-date URL is catb.org/~esr/faqs/smart-questions.html#idp5122192 — törzsmókus
– törzsmókus, Commented Jul 8, 2013 at 13:21

noah · Accepted Answer · 2010-03-01 20:31:10Z

70

This will work:

for (String crt : new String[]{"a","b","c"} ) {
    doSomething();
}

answered Mar 1, 2010 at 20:31

noah

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Comments

Joachim Sauer · Accepted Answer · 2010-03-01 20:54:09Z

22

The Java language provides the {"a","b","c"} form as a shortcut, but it is only possible during assignment. It's possible this is to avoid possible ambiguities during parsing, in some positions {} could be interpreted as a code block.

The right way to do it would be how noah suggests, with new String[]{"a","b","c"}.

edited Mar 1, 2010 at 20:54

Joachim Sauer

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answered Mar 1, 2010 at 20:50

Tom Castle

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2 Comments

Joachim Sauer Over a year ago

Please note that that short form isn't allowed in all assignments. It is allowed only in initializations.

Atmocreations Over a year ago

@Joachim: interesting fact. This pretty much solves my question, thanks for pointing it out. @Tom Castle: +1 Good answer

Chris Dennett · Accepted Answer · 2010-03-01 20:36:12Z

4

Dunno, what about this? :) Pity there's no succinct version. Suppose you could use Groovy or Scala if you wanted anything like that :)

for (String s : Arrays.asList("a","b","c")) {
    hmm(s);
}

answered Mar 1, 2010 at 20:36

Chris Dennett

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Comments

dbrown0708 · Accepted Answer · 2010-03-01 20:41:28Z

4

You want

for (String crt : new String [] {"a","b","c"} ) {
    doSomething();
}

I use IntelliJ and it says put the message "expression expected" on the right-hand side of the colon in the for-loop, which seems more accurate.

I should add that IntelliJ also offers to add the "new String []" automagically for me.

answered Mar 1, 2010 at 20:41

dbrown0708

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