Theoretical: Code smell Java memory leak: create Class the generates immutable objects use Record java 14, obiect immutable, how objects are saved Deep copy vs shallow copy What is a pure function? Try with resources Seal class java 17 stream operation intermediale and final, Lambda and functional interfaces Marker interface default method solid principles. Design patterns; proxy decorator Hibernate proxy Lazy loading , Hibernate cache level 2 , @cachable @transaction : isolation vs propagation and ACID principles Practical: Calculate unique number of occurrences

Code review question for the code which is already well written.