Lambdas, Functional Interfaces and Streams

import java.util.*;

List<String> names = new ArrayList<>(List.of("Ravi", "Asha", "Meera"));

names.sort((a, b) -> a.length() - b.length());     // Comparator lambda
names.forEach(n -> System.out.println(n));
names.forEach(System.out::println);                // method reference

import java.util.stream.*;

record Student(String name, String dept, int marks) {}

List<Student> students = List.of(
    new Student("Asha", "CS", 91), new Student("Ravi", "EE", 74),
    new Student("Meera", "CS", 88), new Student("Kabir", "ME", 69));

// names of CS students scoring above 85, sorted
List<String> top = students.stream()
    .filter(s -> s.dept().equals("CS"))
    .filter(s -> s.marks() > 85)
    .map(Student::name)
    .sorted()
    .collect(Collectors.toList());               // [Asha, Meera]

// average marks per department
Map<String, Double> avg = students.stream()
    .collect(Collectors.groupingBy(Student::dept, Collectors.averagingInt(Student::marks)));

// total, max
int total = students.stream().mapToInt(Student::marks).sum();
Optional<Student> best = students.stream().max(Comparator.comparingInt(Student::marks));