No StackTrace in java.lang.NullPointerException

The compiler in the server VM now provides correct stack backtraces for all "cold" built-in exceptions. For performance purposes, when such an exception is thrown a few times, the method may be recompiled. After recompilation, the compiler may choose a faster tactic using preallocated exceptions that do not provide a stack trace. To disable completely the use of preallocated exceptions, use this new flag: -XX:-OmitStackTraceInFastThrow
http://stackoverflow.com/questions/1142007/why-does-log4j-disable-stack-trace-after-lots-of-repetition-of-the-same-excepti
http://java.sun.com/j2se/1.5.0/relnotes.html#hotspot