JVM architecture Write TreeSet's add method implementation available in java Hashmap and set difference What is hashmap implementation Why do we need to serialize object What are all the methods in serialiazable interface Can i serialize object which does not implementing serialiazable interface What is the scenario for using abstract class and interface What are all the design patterns you know What are all the ways of implementing singleton other than traditional approach What is the features in 1.8 when compared to 1.5 How to do many to many mapping in hibernate Difference between save , Save or Update and merge What is rest api What are all the methods available in rest api Difference between soap and rest api How to get max 4th salary from a table How to make changes to executable for a date format change without restarting server Observable design pattern