The error that you are getting looks really strange.
java.lang.ClassFormatError: Method display in class demoprograms/azrael has illegal modifiers: 0x402
It indicates that the class file is invalid. Somehow the compiler that you are using has accepted illegal code (a method that is both abstract and private) without giving an error message, and produced an invalid class file. That's a bug in the compiler.
Which compiler are you using? Is this the standard javac from the JDK (if so, what version)?
I am very surprised it would allow those two modifiers together. Maybe the class was compiled with a different compiler, or (even) it has been altered after compilation. Or there was an error in transmission or recording of the .class file.