How can you get the max of a collection?

Collections.max is a factory method: you pass it your collection, and optionally a Comparator if your elements aren't naturally Comparable or you want a different ordering.

java
List<Integer> numbers = List.of(3, 7, 2, 9, 4);

int max = Collections.max(numbers); // 9

Two things to watch out for:

• If the collection contains a null element, you get a NullPointerException.
• If the collection is empty, you get a NoSuchElementException.

The second pattern is based on streams: call .stream(), then .max(...), passing a Comparator.

java
List<Integer> numbers = List.of(3, 7, 2, 9, 4);

Optional<Integer> max = numbers.stream().max(Comparator.naturalOrder()); // Optional[9]

Just like Collections.max, you get a NullPointerException if there's a null value in the stream. But if the stream is empty, you get an empty Optional instead of an exception — arguably better for error handling, since the caller can decide how to handle the absence of a value instead of catching an exception.

Be careful with the stream pattern: you still pay the price of creating the stream, which is extra overhead you may want to avoid. Unless you specifically need stream features (chaining with filter, map, etc.), plain old Collections.max is probably your best choice.