Petascope - String concatenation is much slower than StringBuilder

[Bang Pham Huu]

This problem happens for example with WMS GetCapabilities for ten thousands of Layers (each layer is generated to XML string).

In a loop to concatenate the XML string, with a = a + b it takes

real	1m48.479s

With StringBuilder to concatenate these strings in a loop, it will take:

real	0m3.223s

[Dimitar Misev]

Even 3s is a lot. You should precalculate the total length of the XML strings should be concatenated, and then set the capacity of the StringBuilder to this total length.

​https://docs.oracle.com/javase/7/docs/api/java/lang/StringBuilder.html#StringBuilder(int)

[Bang Pham Huu]

How can I suppose to precalculate when the string size of a WMS layer is varied in each loop?