Re: static hashtable with conent?

From:

Owen Jacobson <angrybaldguy@gmail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 25 Nov 2007 00:07:00 GMT

Message-ID:

<2007112416070050073-angrybaldguy@gmailcom>

On 2007-11-24 11:57:48 -0800, "Mike Schilling"
<mscottschilling@hotmail.com> said:

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Use a static init block (And use a HashMap; Hashtable is obsolete)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);
    ...
}

There is a trick for emulating (sort of) map literals in Java that
might be useful here:

static Map<String, Whatever> map = new HashMap<String, Whatever> () {{
  put ("if", IF_TOKEN);
  put ("else", ELSE_TOKEN);
  // ...
}};

It does have the cost of requiring one more class to be loaded. It
will also confuse reflection-based code that expects the 'map' field to
_be_ a specific subtype rather than _assignable to_ a specific subtype.
OTOH, I find both of those concerns are rarely important in my own
code.

Cheers,
O