Comments on: Effective Java Collections

By: admin

admin — Mon, 02 Nov 2009 16:16:46 +0000

Sure. You want to use interfaces as much as possible instead of concrete classes whenever it makes sense.

Suppose that you write your code and then realize that because of performance concerns, you don’t actually want to use an ArrayList, you’d rather use a LinkedList. To an outside user the behavior of both is the same (they conform to the List interface) but the implementation is different. If foo was an ArrayList, then you have to change it everywhere that its used – which means touching a lot of code that you don’t mean to change. If foo is a List, then this is the only line you need to change.

For this specific use case its not a huge deal, but it helps you keep this concept in mind as you do more complex classes.

Check out this interview with Erich Gamma: http://www.artima.com/lejava/articles/designprinciples.html.

By: j2ee

j2ee — Thu, 22 Oct 2009 14:41:43 +0000

Can you please explain why should The left side always an interface!, and not do this: ArrayList foo = new ArrayList();

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By: Christopher Currie

Christopher Currie — Thu, 14 Aug 2008 22:39:47 +0000

Curse your non-HTML escaping comment forms, I did use generics in those examples!

By: Christopher Currie

Christopher Currie — Thu, 14 Aug 2008 22:38:52 +0000

If you’re not constrained to the Java Standard Library, I would prefer to use Google Collections “Immutable” collection objects, for empty collections or otherwise:

List myEmptyList = com.google.common.collect.ImmutableList.of();
List mySingleElementList = com.google.common.collect.ImmutableList.of(1);

and so forth for the other collections. The one disadvantage is that it doesn’t return the same list every time, so you have less memory efficiency, but IMO the consistency of usage outweights this.

Otherwise, good list!