public int add (K key, int amount)
    {
        CountEntry<K> entry = _backing.get(key);
        if (entry == null) {
            _backing.put(key, new CountEntry<K>(key, amount));
            return amount;
        }
        return (entry.count += amount);
    }
public int add ( K key , int amount ) { CountEntry < K > entry = _backing . get ( key ) ; if ( entry == null ) { _backing . put ( key , new CountEntry < K > ( key , amount ) ) ; return amount ; } return ( entry . count += amount ) ; }
Add the specified amount to the count for the specified key, return the new count.
Adding 0 will ensure that a Map.Entry is created for the specified key.