Angular mat-error does not pop up, hided (picture included)...

java.lang.ClassFormatError: Incompatible magic value 218774561...

java.lang.ClassFormatError while loading class...

javamail is not working. MessagingException arises...

Need assistance setting up a class to send email, it gets called from the main class...

java.lang.UnsupportedClassVersionError: yy/ii : Unsupported major.minor version 51.0...

Testng Absent Code attribute in method that is not native or abstract in class file...