Get the environment variable of the operating system in Java

Note: This is to get the environment variables of the operating system instead of JVM-related variables (see my previous blog: Get environment variables in Java ).
It may be to create an atmosphere where the JVM is the operating system platform, or to emphasize the independence of the Java platform. I do not know when Java has discarded the system. getenv (string) function. Therefore, Java can only obtain some of its own Defined variables, but cannot interact with the environment variables of the operating system, you can only set the variables to be passed to Java when running the "-d" parameter.
Therefore, the only way is to judge the operating system first, and then use the operating system command to call up the list of environment variables and try to get the output list. The following is an example from http://www.rgagnon.com/javadetails/java-0150.html: Import java. Io. * ;
Import java. util. * ;

Public   Class Readenv {
  Public   Static Properties getenvvars () throws throwable {
PROCESS p =   Null ;
Properties envvars =   New Properties ();
Runtime R = Runtime. getruntime ();
String OS = System. getproperty ( " OS. Name " ). Tolowercase ();
// System. Out. println (OS );
If (OS. indexof ( " Windows 9 " ) >   - 1 ) {
P=R.exe C ("Command.com/C set");
}
Else   If (OS. indexof ( " NT " ) >   - 1 )
| (OS. indexof ( " Windows 20 " ) >   - 1 )
| (OS. indexof ( " Windows XP " ) >   - 1 )) {
//Thanks to juanfran for the XP fix!
P=R.exe C ("Cmd.exe/C set");
}
Else   {
//Our last hope, we assume Unix (thanks to H. Ware For the fix)
P=R.exe C ("Env");
}
Bufferedreader br =   New Bufferedreader
( New Inputstreamreader (P. getinputstream ()));
String line;
While (Line = BR. Readline ()) ! =   Null ) {
Int Idx = Line. indexof ( ' = ' );
String key = Line. substring ( 0 , Idx );
String Value = Line. substring (idx + 1 );
Envvars. setproperty (Key, value );
// System. Out. println (Key + "=" + value );
}
Return Envvars;
}

Public   Static   Void Main (string ARGs []) {
Try   {
Properties P=Readenv. getenvvars ();
System.Out. Println ("The current value of temp is:" +
P. getproperty ("Temp"));
}
Catch (Throwable E) {
E. printstacktrace ();
}
}
}