I want to use RxTx in a Linux system and in the Wiki documentation it is said that autoconf, automake, libtool are needed. So how to know that they are present in a Linux system ?
The most obvious way is to type the name of the programs in terminal (except for libtool). If they're there, you'll see.
You can also always try to make the program. If any of the needed programs are missing, the make will break and emit errors which can be easily used to track down the missing dependencies.
The second option is to use the package management program to see if the packages for them are installed. Unfortunately, you didn't specify your distribution, so I can't give you specifics.