I have written mine own Security Manger and as well as written BundleProtection domain . Then i have one application that internallu create one thread . Now this all the things are work fine when i compile my application using JDK 1.3 . But when same application i complied in JDK 1.4 than newly created thread from that program is not getting any security .. and that thread is getting security exception .. !!! i dont knw why just compilation is making this differerance .. becouse i tried lot of JRE version but that is not making any difference but only Compilation version of the JDK is making differerace.. How security of newly created thread is changing between JDK 1.3 and JDK 1.4 complitation.. ???