Updated: After referring to the post here: rJava load error in RStudio/R after "upgrading" to OSX Yosemite I have solved the problem. This one was useful too. Loading rJava on Mac OS High Sierra
I am trying to install and require package "XLConnect".
And I have Java installed, when I was trying to update it.
The screenshot I got was as below, showing I have a newer Java version.
 
 
The error messages I've got was as below, and I installed the package "XLConnectJars" as the error message mentioned it. But still did not solve the problem. I wonder have anybody had the same issue before? Any suggestion and assistance would be highly appreciated.
> library("XLConnect")
Loading required package: XLConnectJars
Error: package or namespace load failed for ‘XLConnectJars’:
 .onLoad failed in loadNamespace() for 'rJava', details:
  call: dyn.load(file, DLLpath = DLLpath, ...)
  error: unable to load shared object 
'/Library/Frameworks/R.framework/Versions/3.5/Resources/library/rJava/libs/rJava.so':
dlopen(/Library/Frameworks/R.framework/Versions/3.5/Resources/library/rJava/libs/rJava.so, 6): Library not loaded: /Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home/lib/server/libjvm.dylib
          Referenced from: 
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/rJava/libs/rJava.so
          Reason: image not found
        Error: package ‘XLConnectJars’ could not be loaded
        > install.packages("XLConnectJars")
        trying URL 'https://cran.rstudio.com/bin/macosx/el-capitan/contrib/3.5/XLConnectJars_0.2-15.tgz'
        Content type 'application/x-gzip' length 14810717 bytes (14.1 MB)
        ==================================================
        downloaded 14.1 MB
        The downloaded binary packages are in
            /var/folders/v3/4tfsblxs1m314g6pl2bt4t7r0000gn/T//RtmpBJ5q5u/downloaded_packages
        > library("XLConnectJars")
        Error: package or namespace load failed for ‘XLConnectJars’:
         .onLoad failed in loadNamespace() for 'rJava', details:
          call: dyn.load(file, DLLpath = DLLpath, ...)
          error: unable to load shared object '/Library/Frameworks/R.framework/Versions/3.5/Resources/library/rJava/libs/rJava.so':
          dlopen(/Library/Frameworks/R.framework/Versions/3.5/Resources/library/rJava/libs/rJava.so, 6): Library not loaded: /Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home/lib/server/libjvm.dylib
          Referenced from: 
    /Library/Frameworks/R.framework/Versions/3.5/Resources/library/rJava/libs/rJava.so
              Reason: image not found
