FULL PRODUCT VERSION :
java version "1.6.0_03"
Java(TM) SE Runtime Environment (build 1.6.0_03-b05)
Java HotSpot(TM) 64-Bit Server VM (build 1.6.0_03-b05, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
All - this a bug in the java.net library

A DESCRIPTION OF THE PROBLEM :
InterfaceAddress.equals() NPE when broadcast field == null
This can be seen when comparing InterfaceAddress(es) represneting point-to-point links. The problem occurs because of a missing check when broadcast==null in the equals() method:

 public boolean equals(Object obj) {
if (!(obj instanceof InterfaceAddress)) {
return false;
}
InterfaceAddress cmp = (InterfaceAddress) obj;
if ((address != null & cmp.address == null) ||
(!address.equals(cmp.address)))
return false;
ERROR>> if ((broadcast != null & cmp.broadcast == null) ||
(!broadcast.equals(cmp.broadcast)))
return false;
if (maskLength != cmp.maskLength)
return false;
return true;
    }

When broadcast==null above the OR section is run and broadcast.equals() causes the NPE (because broadcast==null).

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Obtain an InterfaceAddress with broadcast==null. An address for a point-to-point link works well.

Then compare this address (on the left hand side) using equals to another InterfaceAddress.

If broadcast is null a NPE will result.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
true if the InterfaceAddress(es) are equal, false otherwise.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.lang.NullPointerException
at java.net.InterfaceAddress.equals(InterfaceAddress.java:91)
at wb.net.mon.NetworkInterfaceMonitor.traverseNetworkInterfaces(NetworkInterfaceMonitor.java:54)
at wb.net.mon.NetworkInterfaceMonitor.pollAndUpdateMos(NetworkInterfaceMonitor.java:36)
at wb.net.mon.NetworkInterfaceMonitor.access$0(NetworkInterfaceMonitor.java:30)
at wb.net.mon.NetworkInterfaceMonitor$1.run(NetworkInterfaceMonitor.java:26)
at wb.util.thread.ThreadPool.runWorkItem(ThreadPool.java:98)
at wb.util.thread.ThreadPool.doWork(ThreadPool.java:122)
at wb.util.thread.ThreadPool.access$8(ThreadPool.java:107)
at wb.util.thread.ThreadPool$2.run(ThreadPool.java:87)
at java.lang.Thread.run(Thread.java:619)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
Given an InterfaceAddress with a NULL broadcast address:

InterfaceAddress address=//get an interface address with a null broadcast field
address.equals(address));

NOTE: The above equals comparison does not check for this==obj (another issue, but useful for this test since the above statement should always return true, but in fact generates an NPE).
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Write and use a comparator that handles all field comparisons properly.

NOTE: this is a huge problem since InterfaceAddress(es) can not be used in standard ways (e.g. in collections relying on equals, etc.).