What is the proper way to completely replace a StringBuilder?

Question

Looking for the best (?) way to replace contents of a StringBuilder

I normally use this

StringBuilder stringBuilder = new StringBuilder("abc");

stringBuilder.setLength(0);
stringBuilder.append("12");

I guess one could also point to a new StringBuilder

StringBuilder stringBuilder = new StringBuilder("abc");

stringBuilder = new StringBuilder("12");

What are your criteria for "best"? What's the context here? Do you know how long the next final string will be? — Jon Skeet
– Jon Skeet, Commented May 1, 2013 at 19:28
So basically you want to "reset" the StringBuilder? I tend to find that just creating a new one is the most clear way to do it. — Aurand
– Aurand, Commented May 1, 2013 at 19:32

Erik Pragt · Accepted Answer · 2013-05-01 19:33:03Z

3

Reusing a StringBuilder like this usually saves you little to nothing. Personally, I would never bother with these things; just create a new StringBuilder object, it's simple, consistent (you're not resetting your POJO's, right?).

So, I'd say, keep it simple, and go for the second option, unless you've got some interesting constraints not mentioned in your initial post.

answered May 1, 2013 at 19:33

Erik Pragt

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2 Comments

user2287359 Over a year ago

What about if you pass the StringBuilder as param in a method and you need to receive the manipulated StringBuilder back? For example: doMethod(stringBuilder); In this case if you use new StringBuilder("12") in the doMethod, then the caller method will not get the update. Right?

Erik Pragt Over a year ago

Well, set aside that this would be a horrible way of programming (simple rule: never manipulate your input, please read Clean Code), you are right; in that case you'd have to return the new StringBuilder instead.

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