StringBuilder or String? Is there any difference?

It is - and not only the name, when we talk about our program’s performance. I’ll start by explaining how each one works so you’ll understand why this and not that.


string a = "something";

When we declare a string, there’s allocated enough memory to store it’s value, but that’s all.
The problem appears when we try to execute operations on that string.

Take a look at this code:

string a = "some";
a += "string";

The first time our string is declared, it’s allocated memory to store its actual value. But when we modify/extend it, by concatenating the strings guess what happens? The memory used by our initial string is released and the program reallocates memory for the new string. So, if we add to the string 10 characters, one by one, the memory gets reallocated 9 times which makes our program lose performance.


StringBuilder a = new StringBuilder("some", 1000);

The advantage offered by StringBuilder is that it stores the values in an internal buffer which can be directly extended without releasing and reallocationg memory. This buffer has its size specified in stringbuilder’s declaration (in the example above, it’s 1000), if that limit is exceeded, the stringbuilder will create another internal buffer and will merge it with the first one. However is not a good idea to continously allocate memory for these buffers, so try to be precise when you specify the StringBuilder’s size.

So what to use?

StringBuilder - should be used when you want to execute many operations continuously to avoid creating a new string each time.

String - it should be used when you don’t want to do heavy operations (like modifying its value very often/inside a loop).