Java

What could go wrong if the key object field used for computing hashCode is changed after insertion into a HashMap?

Question 5. There are two implementations of the interface, what happens when injecting a variable of interface type into a Spring bean? - The first implementation will be in the variable - A compile-time error will occur - A context startup error will occur - It depends on the Spring version

What needs to be done with the class (with fields longId and List of objects) to make its objects immutable?

Question 8. Is it possible to use the @Transactional annotation on the handle method of ExampleService to ensure consistency?

How to protect against mutation through getter (returning a copy of the list)?