Demo.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

class Student 
{
    int age;
    String name;

    public Student(int age, String name) {  
        this.age = age;
        this.name = name;
    }

    public String toString() {
        return "student [age=" + age + ", name=" + name + "]";
    }
    
    }

public class Demo {
    public static void main(String[] args) {
Comparator<Student> com = (i, j) -> i.age > j.age ? 1 : -1;
     List<Student> studs = new ArrayList<>();
   studs.add(new Student(21,"Navin"));
   studs.add(new Student(12,"John"));
   studs.add(new Student(18,"Parul"));
   studs.add(new Student(20,"Kiran"));
         Collections.sort(studs, com);
        for(Student s: studs){
            System.out.println(s);
        }



     
    }
}