TreeSet null insertion is possible or not in Java? Yes or No

📌 Can You Insert NULL in a TreeSet? | Java Interview Question

❓ Wondering if you can insert a null value in a TreeSet?
Java's TreeSet is part of the SortedSet interface and is implemented using a TreeMap. It sorts elements using natural ordering or a custom comparator.

⚠️ Null Insertion Behavior:
✔️ In Java 6 and earlier, inserting null was allowed if it was the only element.
❌ In Java 7+, inserting null throws a NullPointerException, because TreeSet relies on comparisons and null cannot be compared.

🔹 Key Takeaways:
HashSet ✅ allows null.
TreeSet ❌ does NOT allow null (Java 7+).

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