System.console().readPassword(); does not work in Eclipse3.2

[xmx]

My use jdk6 and Eclipse3.2

When I run the following codes in eclipse:

---------------code begins---------------------------------
public class Test {
public static void main(String[] args) {
System.console().readPassword();
}
}
---------------code ends------------------------------------

I get this:

Exception in thread "main" java.lang.NullPointerException
at HelloWorld.main(HelloWorld.java:3)

But it runs well in command line.

Who can tell me why?
Is this a bug of eclipse or jdk6?
Thanks very much!