Question

I’ve read multiple places that in Java 1.5+ String concatenations are optimized to using a StringBuilder when a program is compiled. It’s unclear to me if this is a standard or just a common optimization many compilers employ. Any clarificion in regards to this would be appreciated, but mainly it’s a lead-in to my second question.

Does .NET similarly optimize? I’m aware that if I use StringBuilder this will eliminate any ambiguity but I personally find the simplicity of + easier to read. If .NET does, did this start in a specific version? Elaboration is appreciated.

Answer 1

Hope this will give you a better view towards StringBuilder then string conctenation with +

Performance Considerations

A String object concatenation operation always creates a new object
from the existing string and the new data. A StringBuilder object
maintains a buffer to accommodate the concatenation of new data. New
data is appended to the buffer if room is available; otherwise, a new,
larger buffer is allocated, data from the original buffer is copied to
the new buffer, and the new data is appended to the new buffer.

The performance of a concatenation operation for a String or StringBuilder object depends on the frequency of memory allocations. A
String concatenation operation always allocates memory, whereas a
StringBuilder concatenation operation allocates memory only if the
StringBuilder object buffer is too small to accommodate the new data.
Use the String class if you are concatenating a fixed number of String
objects. In that case, the compiler may even combine individual
concatenation operations into a single operation. Use a StringBuilder
object if you are concatenating an arbitrary number of strings; for
example, if you’re using a loop to concatenate a random number of
strings of user input.

MSDN