Re: Array of ArrayLists problem

From:

Kevin McMurtrie <mcmurtrie@pixelmemory.us>

Newsgroups:

comp.lang.java.programmer

Date:

Tue, 06 Jul 2010 21:43:53 -0700

Message-ID:

<4c340609$0$22103$742ec2ed@news.sonic.net>

In article <i0vohh$1ep$1@news.eternal-september.org>,
"Mike Schilling" <mscottschilling@hotmail.com> wrote:

"Lew" <lew@lewscanon.com> wrote in message
news:f4a6bdb8-c41e-4978-9abf-70e5791f87f5@c33g2000yqm.googlegroups.com...

Ross wrote:

Let's say that I have a java.util.ArrayList which will contain only
strings. So, I can declare this as:

ArrayList<String> blah = new ArrayList<String>();

So far so good, but let's say that blah is an array in itself. I'd
expect to be able to do this:

ArrayList<String> blah[] = new ArrayList<String>[ 50 ];

However, if I do that, I get a compile time error saying something
about creating a generic array. If I modify the code to:

ArrayList<String> blah[] = new ArrayList[ 50 ];

Then, it compiles and works, but gives me a warning about using a
deprecated blah blah blah.

What gives?

Arrays and generics don't mix. It has to do with arrays being
reifiable but not generics.

From the JLS, ?10.10:
"... creation of arrays of non-reifiable types is forbidden."
<http://java.sun.com/docs/books/jls/third_edition/html/
arrays.html#10.10>

There aren't many instances in Java of "That's how it works. Don't ask why;
you're better off not knowing", but this is one of them.

I'd like to submit this one too:

-----------

public class Foo
{
  class InnerFoo { }
  void method ()
  {
    InnerFoo x[]= new InnerFoo[100]; //Compiles
  }
}

-----------

public class Foo<BAR>
{
  class InnerFoo { }
  void method ()
  {
    InnerFoo x[]= new InnerFoo[100]; //Doesn't compile
  }
}

-----------

public class Foo<BAR>
{
  class InnerFoo { }
  void method ()
  {
    InnerFoo x[]= new Foo.InnerFoo[100]; //Compiles
  }
}
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