Re: static hashtable with conent?
"Mike Schilling" <mscottschilling@hotmail.com> writes:
Kevin wrote:
Did not find out the answer after some google:
how can we create a static hashtable with some initial values there?
static Hashtable ht = new Hasthable();
will only create a empty one. Suppose I want to put some Integer
values as keys and values of this hashtable, how can I do that?
Use a static init block (And use a HashMap; Hashtable is obsolete)
static Map map;
static
{
map = new HashMap();
map.put("if", IF_TOKEN);
map.put("else", ELSE_TOKEN);
...
}
I would prefer a static method returning the map:
static Map map = createMap();
private static final Map createMap() {
Map map = new HashMap();
map.put("if", IF_TOKEN);
map.put("else", ELSE_TOKEN);
}
Or perhaps create a builder:
static Map map = new MapBuilder(new HashMap()).put("if", IF_TOKEN)
.put("else", ELSE_TOKEN)
.toMap();
if it is something that is done often.
I would prefer not to use the clever anonymous subclass of HashMap
with an initializer. It's something that's bound to bite you in the
posterior sooner or later. E.g., if you try to send the map to another
process using serialization - then the receiver should also have the
same anonymous class available. That can be alleviated using
static Map map = new HashMap(new HashMap(){{
put("if", IF_TOKEN);
put("else", ELSE_TOKEN);
}});
i.e., using it more like a builder. Still far too clever to be readily
readable.
However, it seems that the actual problem being solved is a translation
between strings and some contstants/enums/whatever.
That the translation is performed by a map is an implementation detail.
I would create a method
static Token textToToken(String text) { //...
It could initialize its map lazily, or it could use a completely separate
apporach.
/L 'but Map literals would be nice :)'
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