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Re: Concurrent bidirectional one-to-many map?

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On 5/6/2011 1:07 PM, Sebastian wrote:
> Does anyone know of a concurrent bidirectional one-to-many
> map implementation?
>
> By bidirectional I mean that I can lookup keys by values, by
> one-to-many I mean that the value end of the map is a list or
> set, and by concurrent I mean that I do not need to synchronize
> externally and get performance comparable to that of
> java.util.concurrent.ConcurrentHashMap in both directions.
>
> If this beast doesn't exist, how would I go about inventing it?
> I must say that I am by no means any sort of concurrency guru...
>
> -- Sebastian
>


Can you just put both keys and values in as the key?  Something like:

Map<Key,Key> myMap = new ConcurrentHashMap();
// add key k and value v
Key holder = new Key( k, v, KEY );
myMap.put( holder, holder );
holder = new Key( v, k, VALUE )
myMap.put( holder, holder );
...

public class Key<K,V> {
   public enum KeyValue {KEY,VALUE};
   private k key;
   private V value;
   private KeyValue keyOrValue;

   public Key( K key, V value, KeyValue keyOrValue ) {
     this.key = key;
     this.value = value;
     this.keyOrValue = keyOrValue;
   }
// must also override hashcode and equals...
}


This way when you add something, it gets added as both key and value. 
You might want to override "put" to do that automatically.  When you 
look up either a key or a value, you'll find both.

There may be better ways of doing this, it's just the first thing that I 
thought of.  Also the code above is meant more as a sketch than a 
rigorous code example.

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Thread

Concurrent bidirectional one-to-many map? Sebastian <sebastian@undisclosed.invalid> - 2011-05-06 22:07 +0200
  Re: Concurrent bidirectional one-to-many map? markspace <-@.> - 2011-05-06 13:45 -0700
    Re: Concurrent bidirectional one-to-many map? Sebastian <sebastian@undisclosed.invalid> - 2011-05-07 11:43 +0200
      Re: Concurrent bidirectional one-to-many map? Lew <noone@lewscanon.com> - 2011-05-07 07:59 -0400
        Re: Concurrent bidirectional one-to-many map? Lew <noone@lewscanon.com> - 2011-05-07 12:49 -0400
          Re: Concurrent bidirectional one-to-many map? Sebastian <sebastian@undisclosed.invalid> - 2011-05-07 21:34 +0200
      Re: Concurrent bidirectional one-to-many map? Patricia Shanahan <pats@acm.org> - 2011-05-07 06:40 -0700
        Re: Concurrent bidirectional one-to-many map? Tom Anderson <twic@urchin.earth.li> - 2011-05-08 04:51 +0100
          Re: Concurrent bidirectional one-to-many map? Robert Klemme <shortcutter@googlemail.com> - 2011-05-09 06:43 -0700
            Re: Concurrent bidirectional one-to-many map? Tom Anderson <twic@urchin.earth.li> - 2011-05-09 18:28 +0100
              Re: Concurrent bidirectional one-to-many map? Sebastian <sebastian@undisclosed.invalid> - 2011-05-09 22:57 +0200
                Re: Concurrent bidirectional one-to-many map? Lew <noone@lewscanon.com> - 2011-05-09 18:36 -0400
                Re: Concurrent bidirectional one-to-many map? Tom Anderson <twic@urchin.earth.li> - 2011-05-10 08:34 +0100
                Re: Concurrent bidirectional one-to-many map? Sebastian <sebastian@undisclosed.invalid> - 2011-05-11 10:09 +0200
                Re: Concurrent bidirectional one-to-many map? Sebastian <sebastian@undisclosed.invalid> - 2011-05-11 10:51 +0200
                Re: Concurrent bidirectional one-to-many map? Robert Klemme <shortcutter@googlemail.com> - 2011-05-11 04:55 -0700
                Re: Concurrent bidirectional one-to-many map? Lew <noone@lewscanon.com> - 2011-05-11 09:00 -0400
                Re: Concurrent bidirectional one-to-many map? Sebastian <sebastian@undisclosed.invalid> - 2011-05-11 20:47 +0200
      Re: Concurrent bidirectional one-to-many map? markspace <-@.> - 2011-05-07 09:35 -0700
      Re: Concurrent bidirectional one-to-many map? Michal Kleczek <kleku75@gmail.com> - 2011-05-09 16:42 +0200
  Re: Concurrent bidirectional one-to-many map? Roedy Green <see_website@mindprod.com.invalid> - 2011-05-07 03:46 -0700

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