When you see Set<Integer>[] rowSets = new HashSet[9];, your brain might freeze. What's the array? What are the elements? Why HashSet without <Integer>? And wait - if arrays like int[] are type-safe, why do we even need generics? Let's untangle this confusing syntax and understand why Java works this way.
"Why make something private? Just make everything public. If the coder knows which method to call, they call it. Problem solved, right?" That was me a week ago. I was so wrong. Here's my journey from "public/private is just fancy nonsense" to "holy crap, this actually makes sense!" 🤯
"What does ResponseEntity<UnlockResponse> mean? Why can I use <UnlockResponse> here but <LoginResponse> somewhere else?" ResponseEntity is like a delivery box - it's a generic container that can hold any type of content. The <T> is a placeholder that you fill with your specific data type. Let's understand how this "magic" works and why it's incredibly powerful.