Working with immutable collections

[Gernot Neppert]

I'd rather have an "unmodifiable" member function in 
java.util.Collection, together with a "synchronized" function, something 
like this:

public interface Collection<E> {

/**
   Returns an unmodifiable view of this Collection.
   @return an unmodifiable view of this Collection (may be {@code this} 
instance if is already unmodifiable).
public Collection<E> unmodifiable() default {
       return Collections.unmodifiableCollection(this);
     }

/**
   Returns a synchronized view of this Collection.
@param lock the Lock to use.
   @return a view of this Collection that executes all operations while 
holding a Lock. (may be {@code this} instance if is already synchronized 
on the supplied Lock).
@throws IllegalArgumentException if this Collection is already 
synchronized on a different Lock.
public Collection<E> synchronize(Lock lock) default {
       return Collections.synchronize(this, lock);
     }

}


These should of course be co-variantly overriden in java.util.List, 
java.util.Set etc.!






Am 19.11.2012 15:39, schrieb Johan Haleby:
> Hi,
>
> I'm sorry if this has been discussed before but here goes:
>
> Let's say I have an immutable list called "xList" that I want to filter and
> return the result as a new *immutable* list. I could do something like this:
>
> Collections.unmodifiableList(xList.filter(obj -> obj.something()).into(new
> ArrayList<X>())));
>
> How ever I think this is quite verbose and doesn't follow the fluent style
> of the API. What I would like to have is something a long these lines:
>
> xList.filter(obj -> obj.something()).intoImmutable(new ArrayList<X>()));
>
> "intoImmutable" could then do "Collections.unmodifiableList(..)" for me so
> I don't need to wrap all statements where I want to return an immutable
> collection.
>
> What are your thoughts on this?
>
> Regards,
> /Johan
>