java实现Linux命令?

try {
String[] cmd = new String[]{”/bin/sh”, “-c”, ” ls “};
Process ps = Runtime.getRuntime().exec(cmd);

BufferedReader br = new BufferedReader(new InputStreamReader(ps.getInputStream()));
StringBuffer sb = new StringBuffer();
String line;
while ((line = br.readLine()) != null) {
sb.append(line).append(”n”);
}
String result = sb.toString();

System.out.println(result);
} catch (Exception e) {
e.printStackTrace();
}

总是报 Cannot run program "/bin/sh": CreateProcess error=3 ??????