Practice with equals and hashCode

One Line At A Time

SEE Ivan TIP below. >> You just got 10+ hours back to see daylight ...

Code -> Generate -> Generate equals() and hashCode(). Click the suitable fields and finito 🤓

Here is a good explanation of the equals and hashcode methods for help on the tasks above: https://codegym.cc/groups/posts/264-equals-and-hashcode-methods-best-practices

Seems like you can use Objects.equals() or Objects.compare(), but that sort of beats the point of the lesson I suppose.

I passed easily every task just using the automatic "Generate hashCode() and equals()..." of the IDE. But I didn't really understand these codes, and so far Code Gym hasn't explained what we need to complete these tasks. Will these methods be better explained and exemplified in this course, or will I have to research them somewhere else? The codes that passed the verification are much more sophisticated and complex than the ones of the examples in this lesson. Is it really expected from us, learners, to solve these tasks by our own, without copying/pasting? Or the purpose is indeed to make extra research, copy/paste, and then understand it only in the future?

Effective Java has a good section on this topic.

there is Objects class

Objects.compare(o1, o2);

return Objects.equals(last, solution.last);

Alt+Insert in IntelIDEA

Big hint for all three tasks: do not try to fix their code, remove their equals and hash methods and write them from scratch and you will pass the test. The only thing to watch out is to check explicitly if the object in comparison is an instance of Solution (as opposed to checking for generic getClass() != secondObject.getClass())