Get SocketException when trying to get Mac address.

I got SocketException when trying to get mac address from a solaris machine:

JDK: 1.6.26.
Solaris:
Release: 5.10
Kernel architecture: sun4u
Application architecture: sparc
Hardware provider: Oracle Corporation
Domain: Kernel version: SunOS 5.10 Generic_147440-01

java code:
Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces();
while (en.hasMoreElements()) {
NetworkInterface intf = en.nextElement();
byte[] mac = intf.getHardwareAddress();
...
}

Stacktrace:
java.net.SocketException: Invalid argument
     at java.net.NetworkInterface.getMacAddr0(Native Method)
     at java.net.NetworkInterface.getHardwareAddress(NetworkInterface.java:385)

Hardware and environment:
The Solaris is on one of four domains on a M5000 server, it has its own set of hardware resources which includes the network interface.
If you run shell script commands like 'arp –a' or '/usr/bin/netstat -pn', it would display correct mac address.
But if you are using Java NetworkInterface.getHardwareAddress() api, it will throw SocketException.

Any suggestion is welcomed.