Stream#max()

max,minは、Comparatorを渡す

public class Outer {
    public static void main(String[] args) {
        List<String> l = List.of("C","X","A");
        l.stream().max((a,b) -> a.compareTo(b)).ifPresent(System.out::println);
        l.stream().min((a,b) -> a.compareTo(b)).ifPresent(System.out::println);
    }
}

X
A