java读取环境变量

import java.io.BufferedReader;      
import java.io.InputStreamReader;      
import java.util.Properties;      
     
class Test      
{      
 // 返回当前系统变量的函数，结果放在一个Properties里边，这里只针对win2k以上的，其它系统可以自己改进      
 public Properties getEnv() throws Exception      
 {      
  Properties prop = new Properties();      
  String OS = System.getProperty("os.name").toLowerCase();      
  System.out.println("操作系统:" + OS);      
  Process p = null;      
  if (OS.indexOf("windows") > -1)      
  {      
   p = Runtime.getRuntime().exec("cmd /c set");      
  }      
   if(OS.indexOf("linux") > -1)      
         {      
            p = Runtime.getRuntime().exec("sh -c set");      
         }      
  BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));      
  String line;      
  while ((line = br.readLine()) != null)      
  {      
   int i = line.indexOf("=");      
   if (i > -1)      
   {      
    String key = line.substring(0, i);      
    String value = line.substring(i + 1);      
    prop.setProperty(key, value);      
   }      
  }      
  return prop;      
 }      
     
 // 具体用法      
 public static void main(String[] args)      
 {      
  try     
  {      
   Test sp = new Test();      
   Properties p = sp.getEnv();      
   System.out.println(p.getProperty("PATH")); // 注意大小写，比如读取PATH。Linux下为PATH；Windows为Path      
  }      
  catch (Exception e)      
  {      
   System.out.println(e);      
  }      
 }      
}