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Date: Wed, 2 Jan 2013 04:51:04 -0800 (PST)
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Subject: Why is that in JDK8: value used in lambda expression shuld be effectively final?
From: jeti789@web.de
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Xref: csiph.com comp.lang.java.programmer:20869

I'm currently plaing with JDK8 and using lambda-8-b69-windows-i586-17_dec_2012. I wonder why this does not compile:

List<Integer> ints = new ArrayList<>();
ints.add(1);
ints.add(2);
ints.add(3);

int sum = 0;
ints.forEach(i -> {sum += i;});

The compiler error is "value used in lambda expression shuld be effectively final"

However, this here compiles:

int sumArray[] = new int[] { 0 };
ints.forEach(i -> {sumArray[0] += i;});

I'm a bit confused now. Does this mean that JDK8 closures are no true closures or is this a bug in my IDE (IDEA 12)?

Thanks, Oliver