code: public int replace(final int key, final int value)
      {
          int curValue = get(key);
          if (curValue != missingValue)
          {
              curValue = put(key, value);
          }
  
          return curValue;
      }
docs: Primitive specialised version of {@link #replace(Object, Object)}
  
  @param key key with which the specified value is associated
  @param value value to be associated with the specified key
  @return the previous value associated with the specified key, or
  {@link #missingValue()} if there was no mapping for the key.