What is the difference between `Collectors.toUnmodifiableList()` and `Collections.unmodifiableList(Collectors.toList())`?

Question

Java Professional — Hard

What is the difference between `Collectors.toUnmodifiableList()` and `Collections.unmodifiableList(Collectors.toList())`?

Accepted Answer

`Collectors.toUnmodifiableList()` guarantees an unmodifiable list with no nulls in Java 10+, while `Collections.unmodifiableList(Collectors.toList())` wraps a mutable list that still allows null values. This difference is crucial for ensuring immutability and handling null values effectively.