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String usrHome = System.getProperty("user.home");
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Key                     Meaning
-------------------     ------------------------------
"file.separator"        File separator (e.g., "/")
"java.class.path"       Java classpath
"java.class.version"    Java class version number
"java.home"             Java installation directory
"java.vendor"           Java vendor-specific string

"java.vendor.url"       Java vendor URL
"java.version"          Java version number
"line.separator"        Line separator
"os.arch"               Operating system architecture
"os.name"               Operating system name

"path.separator"        Path separator (e.g., ":")
"user.dir"              User's current working directory
"user.home"             User home directory
"user.name"             User