Keep Coding

I have gateway.properties file and it has following content:
current.path=c:/projects/sdk/
log.path=storage/logs
Here, in this file:
Either, I want to add third variable which is current.log.path and its value must be:
current.log.path=current.path + log.path
Or, I want to append string to current.path variable as below:
current.path=current.path+log.path
I have a situation that I can't do this concatenation/append job in my Java file. In Java its pretty simple but I have no idea how to do within file itself.

There is no built-in mechanism to have something like variables in a property file. You could try Apache Commons Configuration. I think it is what you are looking for.