When is stringbuilder faster

Edit: The earlier I made this case with only Java 8. Turns out I was wrong. So I stand correct myself. It has nothing to do with java 8. Thanks for visiting DZone today,. Edit Profile. Sign Out View Profile. Over 2 million developers have joined DZone. Concatenating strings is useful, but expensive. Fortunately, you don't need to use StringBuilder anymore - the compiler can handle it for you.

Like Note that your way of measuring the time is heavily flawed. I have seen it many times already that someone made a measurement like this with the outcome of 10ms vs ms and concluded that the first must be faster, although it was actually a lot slower in practice. You have to use a framework like JMH to get useable results. Add a comment. Active Oldest Votes. Do you understand how it works internally? Improve this answer. Marco Acierno Marco Acierno Donagh Hatton Donagh Hatton 4 4 silver badges 6 6 bronze badges.

Shardul Negi Shardul Negi 51 3 3 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. As when extracting a string from a string, StringBuilder offers advantages over the String class when joining strings. As you can see in Figure 4, using AppendJoin of the StringBuilder class is again faster and more resource efficient than using Join of the String class.

When using StringBuilder, you can also set the capacity of the StringBuilder instance to improve performance. If you know the size of the string you will be creating, you can set the initial capacity when creating a StringBuilder instance.

This can reduce the memory allocation considerably. On a final note, the String. Create method is yet another way to improve string handling performance in. NET Core. It provides an efficient way to create strings at runtime. Create in a future post here. Net, as well as a speaker and author of several books and articles. He has more than 20 years of experience in IT including more than 16 years in Microsoft. Net and related technologies. Here are the latest Insider stories. Join can look through all of the strings to work out the exact length it needs, then go again and copy all the data.

This means there will be no extra copying involved. The only downside is that it has to go through the strings twice, which means potentially blowing the memory cache more times than necessary. If you don't have the strings as an array beforehand, it's probably faster to use StringBuilder - but there will be situations where it isn't.

If using a StringBuilder means doing lots and lots of copies, then building an array and then calling String. Join may well be faster. Join vs a bunch of calls to StringBuilder. In the original question, we had two different levels of String. Join calls, so each of the nested calls would have created an intermediate string.

In other words, it's even more complex and harder to guess about. I would be surprised to see either way "win" significantly in complexity terms with typical data. Basically if you have an array where each element is about twice the size of the previous one, and you get it just right, you should be able to force a copy for every append of elements, not of the delimiter, although that needs to be taken into account too.

At that point it's nearly as bad as simple string concatenation - but String.