1- Class loader in java
2- How to use 2 different database configuration in spring boot using repository pattern
3- Design pattern used
4-Transaction in spring boot
5- Array list vs Vector
6- Hashmap key value pair, why key are immutable
7-Immutable class
8-Singleton pattern
9-how dependency injection works in Spring
10- what are features in spring framework
11-Java stream
12 -Multi threading in java
13-spring boot batch api
14 which build is used for build
