Re: are lambdas a way to bring functional programming to java?

From:
=?ISO-8859-15?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>
Newsgroups:
comp.lang.java.programmer
Date:
Tue, 01 Jul 2014 22:32:40 -0400
Message-ID:
<53b36f49$0$293$14726298@news.sunsite.dk>
On 7/1/2014 10:27 PM, Arne Vajh?j wrote:

On 6/28/2014 8:43 AM, Wanja Gayk wrote:

In article <53ae0af4$0$302$14726298@news.sunsite.dk>, Arne Vajh?j
(arne@vajhoej.dk) says...

Here is a simple example.

Java 7 code:

Collections.sort(lst, new Comparator<String>() {
      public int compare(String s1, String s2) {
          return s1.length() - s2.length();
      }
});

Java 8 code:

Collections.sort(lst, (s1,s2) -> s1.length() - s2.length());

I do not see any value in the extra code in the 7 version.


I fear Java8's Lambdas may not encourage reuse so much as the Java 7
way. This does seem to be a pretty standard comparator, so I would
probably code it this way:

static final Comparator<String> COMPARE_BY_LENGTH = new Comparator<>{
       public int compare(String s1, String s2) {
           return s1.length() - s2.length();
       }
  });

Collections.sort(lst, COMPARE_BY_LENGTH);

Just because using it looks better.
Of course in Java 8 it could look like this (sorry for the bad line
breaks:

static final Comparator<String> COMPARE_BY_LENGTH
               = (s1,s2) -> s1.length() - s2.length()

Collections.sort(lst, COMPARE_BY_LENGTH);

..or even implementing a more general interface.
But would people do that very often, if the original expression is so
concise? Hmm..


I look at it a bit differently: the introduction of lambda
makes the benefits of reusing close to zero and we only like
reuse when it actually has benefits, so I do not see it as
a problem.


BTW somewhat off-topic, I do not like the COMPARE_BY_LENGTH thingy.

It is almost like:

public static final int TWO = 2;

* The name does not really explain more than the value
* The value is given by the name so the value can never be changed
   without changing the name

The paradigm actually creates more work when something has to be
changed without improving readability.

Obviously we could have COMPARE_BY_XYZ where XYZ is something
business logic related - that we may want to change the semantics
for.

Arne

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