Hello lima,
Welcome to the forum! It is looking for an installation of java which it cannot find.
Best way to address this:
- Install Java
- Re-install
rJava
- Try again to install
xlsx. If it doesn't work you need to just change the directory so it is able to find the Java location.
(In the event of it not finding the location it will look something like this to set the directory:
Sys.setenv(JAVA_HOME="C:\\Program Files\\Java\\jre7") # for 64-bit version
Sys.setenv(JAVA_HOME="C:\\Program Files (x86)\\Java\\jre7") # for 32-bit version
library(rJava)