在底层获取安卓wifi的mac地址

public static String  getLocalMac() {    String mac=null;    String str = "";    try    {        Process           pp    = Runtime.getRuntime().exec("cat /sys/class/net/wlan0/address ");        InputStreamReader ir    = new InputStreamReader(pp.getInputStream());        LineNumberReader  input = new LineNumberReader(ir);        for (; null != str;)        {            str = input.readLine();            if (str != null)            {                mac = str.trim();// 去空格                break;            }        }    } catch (IOException ex) {        // 赋予默认值        ex.printStackTrace();    }    return mac;}