why same jdk javac different class?

Question

some person tell me different class caused by different machines or time,but sometimes,different time or machines javac same class,i could not get it ><

Answer 1

Please explain your question

Answer 2

same .java,sometimes javac to different .class with same jdk，why?

Answer 3

You said exactly the same, EXPLAIN PLEASE

Answer 4

Also use something called grammar & English