Re: Generic generics help

From:
lscharen@d.umn.edu
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 28 Aug 2008 23:19:50 -0700 (PDT)
Message-ID:
<70d7267b-24b1-4e21-97cf-545c011e94d3@v39g2000pro.googlegroups.com>
On Aug 29, 12:11 am, "wizard of oz" <nos...@gtajb.com> wrote:

My first step is that in my add method, I need to ensure that my row and
column keys are in my list. I would like to use one common routine for th=

is.

The problem is I can't figure out the right generics syntax.


I think you need to do something like this (untested code). BTW, why
iterate through the set? The contains() method is meant to be used
for membership testing.

     private <K> void ensureExists (TreeSet<K> treeSet, K key) {
         if ( !treeSet.contains( key ))
             treeSet.add( key );
     }

Honestly, since a set is guaranteed to not have duplicate items, you
don't need the ensureExists() method at all. You could write your add
method as:

    private Map<R, Map<C, E>> sparseMap = new HashMap<R, Map<C, E>>();

    public void add (R rowKey, C colKey, E element) {

        if ( !sparseMap.containsKey( rowKey ))
            sparseMap.put( rowKey, new HashMap<C, E>() );

        sparseMap.get( rowKey ).put( colKey, element );
    }

-Lucas

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