MoreObjects.ToStringHelper allow user to specify Appendable

Currently the ToStringHelper class constructs a StringBuilder with an initial capacity of 32 in the toString method

 @Override
    public String toString() {
      // create a copy to keep it consistent in case value changes
      boolean omitNullValuesSnapshot = omitNullValues;
      String nextSeparator = "";
      StringBuilder builder = new StringBuilder(32).append(className).append('{');

I think it would be useful to add an instance field to ToStringHelper that holds a Appendable instance that can be given to it, or defaulted to the new StringBuilder(32). Also additional factory methods would be added toMoreObjects to allow the user to specify said instance, e.g. public static ToStringHelper toStringHelper(Appendable buffer, Object self) . This would allow reuse of StringBuilders as opposed to creating them every time.

[kluever]

I still think providing more flexibility here isn’t a great idea. ToStringHelper already builds up a linked list of wrapped entries, so it’s not designed to be high performance. I worry that by providing the overload, we’re going to have users trying to count the number of characters in their toString()s by hand, and that seems wasteful.

StringBuilder expands by doubling it’s internal buffer…the string would have to be pretty enormous for this to happen more than a few times.

[kluever]

Are you noticing actual performance problems from this API?

ToStringHelper is designed to make writing toString()'s easy. If you require a super performant implementation of toString(), you’re probably better off rolling your own.