Re: why people use "Map m= new HashMap()" or "List l = new ArrayList()"?
Patricia Shanahan wrote:
Knute Johnson wrote:
Lew wrote:
Knute Johnson wrote:
It doesn't make a lot of sense to me. Generics were added to
closely control the type of parameters passed to a class that we
then want to make less type specific? It makes no sense to turn a
LinkedList for example into a plain List as you lose all of what
makes it a LinkedList. Of course you could assign it to a Deque.
Well, duhy, if you need the specific type you use the specific type.
No one is saying to be stupid about it.
The only two classes extended from List that you would ever want to do
this with are ArrayList and Vector. Since everyone hates Vector,
explain to me in what actual case this would be of any benefit and not
just confusing.
knute...
You might choose LinkedList because you need e.g. a Queue. On the other
hand, it is also reasonable to choose LinkedList because you need a List
and preliminary estimates suggest that non-tail insertions and removals
will dominate over indexed access.
I would use List, except for the actual constructor call, in the second
case.
I simply point to the body of literature, such as Joshua Bloch's /Effective
Java/, that make the case for this practice. They provide much better
arguments than I will here in favor of it. That's where I learned it -
reading the experts. Instead of challenging me to justify the practice, write
to them.
--
Lew
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