code: public static String STOREtoString() {
      int[] cnts = new int[1];
      Object[] kvs = H2O.STORE.raw_array();
      // Start the walk at slot 2, because slots 0,1 hold meta-data
      for( int i=2; i<kvs.length; i += 2 ) {
        // In the raw backing array, Keys and Values alternate in slots
        Object ov = kvs[i+1];
        if( !(ov instanceof Value) ) continue; // Ignore tombstones and Primes and null's
        Value val = (Value)ov;
        if( val.isNull() ) { Value.STORE_get(val._key); continue; } // Another variant of NULL
        int t = val.type();
        while( t >= cnts.length ) cnts = Arrays.copyOf(cnts,cnts.length<<1);
        cnts[t]++;
      }
      StringBuilder sb = new StringBuilder();
      for( int t=0; t<cnts.length; t++ )
        if( cnts[t] != 0 )
          sb.append(String.format("-%30s %5d\n",TypeMap.CLAZZES[t],cnts[t]));
      return sb.toString();
    }
docs: Nice local-STORE only debugging summary