下载了xlsx包之后，想要运行，出现了以下的字符

> library(xlsx)
Error: package or namespace load failed for ‘xlsx’:
loadNamespace()里算'rJava'时.onLoad失败了，详细内容：
  调用: fun(libname, pkgname)
  错误: JAVA_HOME cannot be determined from the Registry

百度之后，看到有人是这么操作的，就试了下，然后又出现了这样的字符，
> install.packages("rJava",type='source')
Installing package into ‘C:/Users/lenovo/Documents/R/win-library/3.5’
(as ‘lib’ is unspecified)
trying URL 'https://cran.rstudio.com/src/contrib/rJava_0.9-10.tar.gz'
Content type 'application/x-gzip' length 672577 bytes (656 KB)
downloaded 656 KB

* installing *source* package 'rJava' ...
** 成功将'rJava'程序包解包并MD5和检查
Warning in system("sh ./configure.win") : 'sh' not found
ERROR: configuration failed for package 'rJava'
* removing 'C:/Users/lenovo/Documents/R/win-library/3.5/rJava'
* restoring previous 'C:/Users/lenovo/Documents/R/win-library/3.5/rJava'
In R CMD INSTALL
Warning in install.packages :
  installation of package ‘rJava’ had non-zero exit status

我的电脑和安装Rstudio都是64位的，不知道是出了什么问题，麻烦各位高手帮下忙,万分感谢！