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Re: Why is that in JDK8: value used in lambda expression shuld be effectively final?

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> I'm sure you're just using this example to explore what's available,

Yes, exactly. This little code snippet to calcualate a sum is a very simple but canonical case of a closure that has a free variable:

"When a function refers to a variable defined outside it, it's called a free variable. A function that refers to a free lexical variable is called a closure.". Paul Graham, ANSI Common Lisp, Prentice Hall, 1996, p.107.

So free variables aren't possible with JDK8 lambdas. For people used to closures, this is surely surprising. Well, this does not render JDK8 lambdas useless. On the contrary, an imense amount of boilerplate code that is necessary without them can be removed with them. Once the JDK8 gets released this will be an eye-opener to about 95% of all Java developers (the ratio of Java developers not understanding closures ...).

> I think it would be a mistake to discard Java based on it.

If I could I would have done that a long time ago. But not going with a M$ language was a deliberate decision and on the JVM nothing will rival Java (only be a complement like Groovy, or scratch on it like Scala or Kotlin). 

> int sum = ints.reduce(0, (x, y) -> x + y); 

Nice, but it does not compile with me. I use IDEA 12 and the lambda-8-b69-windows-i586-17_dec_2012 JDK. Seems like reduce does not exist in Iterator or Collection!?

-- Oliver

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Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? jeti789@web.de - 2013-01-02 07:08 -0800
  Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? jeti789@web.de - 2013-01-02 07:52 -0800
  Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Steven Simpson <ss@domain.invalid> - 2013-01-02 17:33 +0000
    Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Saxo <jeti789@web.de> - 2013-01-02 11:31 -0800
      Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Lew <lewbloch@gmail.com> - 2013-01-02 12:52 -0800
        Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-01-02 20:58 -0400
          Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Lew <lewbloch@gmail.com> - 2013-01-02 17:40 -0800
            Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-01-03 20:43 -0400
        Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Saxo <jeti789@web.de> - 2013-01-02 23:44 -0800
          Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Patricia Shanahan <pats@acm.org> - 2013-01-03 07:57 -0800
            Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Lew <lewbloch@gmail.com> - 2013-01-03 13:22 -0800
              Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Patricia Shanahan <pats@acm.org> - 2013-01-03 16:14 -0800
      Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Steven Simpson <ss@domain.invalid> - 2013-01-02 21:46 +0000
        Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Lew <lewbloch@gmail.com> - 2013-01-02 17:35 -0800
        Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Saxo <jeti789@web.de> - 2013-01-03 02:13 -0800
          Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Saxo <jeti789@web.de> - 2013-01-03 06:45 -0800
            Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Steven Simpson <ss@domain.invalid> - 2013-01-04 21:32 +0000
              Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-01-04 14:38 -0800
                Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Steven Simpson <ss@domain.invalid> - 2013-01-04 23:45 +0000
                Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-01-04 17:24 -0800
                Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Steven Simpson <ss@domain.invalid> - 2013-01-05 13:20 +0000
              Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Saxo <jeti789@web.de> - 2013-01-05 01:50 -0800
                Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Steven Simpson <ss@domain.invalid> - 2013-01-05 11:21 +0000
                Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Saxo <jeti789@web.de> - 2013-01-05 04:27 -0800
                Re: Why is that in JDK8: value used in lambda expression shuld be effectively final? Steven Simpson <ss@domain.invalid> - 2013-01-05 12:58 +0000

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