Pregunta de entrevista de Capgemini

what OOps in java? what are the Java8 features? where we used in your projects? what is the String? why string immutable in java? where we using collections in your project? Difference between List and set? internal working of Hashmap? difference between Spring and Springboot? How Handle Exception in java& Spring boot? what are the facing challenges in the current project? difference between comparable and comparator? @Exception handler?