下面是一个win下的例子,编译成功之后,运行java Diskspace yourdir(比如c:\) 
import java.io.BufferedReader; import java.io.InputStreamReader;  /** * Determine free disk space for a given directory by  * parsing the output of the dir command. * This class is inspired by the code at * Works only under Windows under certain circumstances. * Yes, it's that shaky. * Requires Java 1.4 or higher. * @[EMAIL PROTECTED]  *Marco Schmidt */ public class Diskspace {  private Diskspace()  {   // prevent instantiation of this class  } 
/** * Return available free disk space for a directory. * @[EMAIL PROTECTED] dirName name of the directory * @[EMAIL PROTECTED] free disk space in bytes or -1 if unknown */ 
 public static long getFreeDiskSpace(String dirName)  {   try   {    // guess correct 'dir' command by looking at the     // operating system name    String os = System.getProperty("os.name");    String command;    if (os.equals("Windows NT") ||os.equals("Windows 2000"))    {     command = "cmd.exe /c dir " + dirName;    }    else    {     command = "command.com /c dir " + dirName;    }    // run the dir command on the argument directory name    Runtime runtime = Runtime.getRuntime();    Process process = null;    process = runtime.exec(command);    if (process == null)    {     return -1;    }    // read the output of the dir command    // only the last line is of interest     BufferedReader in = new BufferedReader(new InputStreamReader(process.getInputStream()));    String line;    String freeSpace = null;    while ((line = in.readLine()) != null)    {     freeSpace = line;    }    if (freeSpace == null)    {     return -1;    }    process.destroy(); 
   // remove dots & commas & leading and trailing whitespace    freeSpace = freeSpace.trim();    freeSpace = freeSpace.replaceAll("\\.", "");    freeSpace = freeSpace.replaceAll(",", "");    String[] items = freeSpace.split(" ");    // the first valid numeric value in items after(!) index 0    // is probably the free disk space    int index = 1;    while (index < items.length)    {     try     {      long bytes = Long.parseLong(items[index++]);      return bytes;     }     catch (NumberFormatException nfe)     {     }    }    return -1;   }   catch (Exception exception)   {     return -1;   }   } 
/** * Command line program to print the free diskspace to stdout * for all 26 potential root directories A:\ to Z:\ * (when no parameters are given to this program) * or for those directories (drives) specified as parameters. * @[EMAIL PROTECTED] args program parameters */    public static void main(String[] args)  {   if (args.length == 0)   {    for (char c = 'A'; c <= 'Z'; c++)    {     String dirName = c + ":\\";     System.out.println(dirName + " " +     getFreeDiskSpace(dirName));    }   }   else   {    for (int i = 0; i < args.length; i++)    {     System.out.println(args[i] + " " + getFreeDiskSpace(args[i]));    }   }  } }   
  方法二:使用Jconfig,可以跨平台 
  从http://www.tolstoy.com/samizdat/jconfig.html上下载jconfig。 
  下载的包的sample里有很简单的例子,如果是要得到磁盘空间的话: 
  用FileRegistry.getVolumes()得到DiskVolume。 
  然后call getFreeSpace()和getMaxCapacity()。 
  就是这么简单。 
  方法三:jni 
  这个是解决所有和os相关的操作的万能利器了。 
  例子我也懒得写了。 
  写一个dll然后call之即可。  
 
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