J.P. Morgan Interview Question

1. what is jvm, jre, jdk which physically exists 2. aggregations, composition difference. usecases in ur current project 3. how to use set( given some input and wt s output) 4. what is main static method, what exception/error u get when u remove static from main method. 5. Can write a java class with out name ex ".java" can u compile n execute it. 6. different types of memories in java 7. Given string where it is stored in string pool/heap 8. why string is immutable ?? 9. How to make a class immutable. 10. Few agile related questions as I am into agile.