code: @Override
    public VALUE get(KEY key) {
      return key != null ? this.map.get(key) : null;
    }
docs: Gets the {@link VALUE value} mapped to the given {@link KEY} in this {@link Cache}.
  
  Returns {@literal null} if the {@link VALUE value} for the given {@link KEY key} is {@literal null},
  or this {@link Cache} does not contain an entry with the given {@link KEY key}.
  
  @param key {@link KEY key} used to lookup the desired {@link VALUE value}.
  @return the {@link VALUE value} mapped to the given {@link KEY key}.
  @see #put(Comparable, Object)