// Java program to demonstrate working of Comparator
// interface
import java.util.*;
import java.lang.*;
import java.io.*;

// A class to represent a student.
class Student
{
    int rollno;
    String name, address;

    // Constructor
    public Student(int rollno, String name,
                   String address)
    {
        this.rollno = rollno;
        this.name = name;
        this.address = address;
    }

    // Used to print student details in main()
    public String toString()
    {
        return this.rollno + " " + this.name +
                " " + this.address;
    }
}

class Sortbyroll implements Comparator<Student>
{
    // Used for sorting in ascending order of
    // roll number
    public int compare(Student a, Student b)
    {
        return a.rollno - b.rollno;
    }
}

class Sortbyname implements Comparator<Student>
{
    // Used for sorting in ascending order of
    // roll name
    public int compare(Student a, Student b)
    {
        return a.name.compareTo(b.name);
    }
}
class Main
{
    public static void main (String[] args)
    {
        ArrayList<Student> ar = new ArrayList<Student>();
        ar.add(new Student(111, "bbbb", "london"));
        ar.add(new Student(131, "aaaa", "nyc"));
        ar.add(new Student(121, "cccc", "jaipur"));

        System.out.println("Unsorted");
        for (int i=0; i<ar.size(); i++)
            System.out.println(ar.get(i));

        Collections.sort(ar, new Sortbyroll());

        System.out.println("\nSorted by rollno");
        for (int i=0; i<ar.size(); i++)
            System.out.println(ar.get(i));

        Collections.sort(ar, new Sortbyname());

        System.out.println("\nSorted by name");
        for (int i=0; i<ar.size(); i++)
            System.out.println(ar.get(i));
    }
}
// for more than one field

// Java program to demonstrate working of Comparator
// interface more than one field

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

class Student {

    // instance member variables
    String Name;
    int Age;

    // parameterized constructor
    public Student(String Name, Integer Age) {
        this.Name = Name;
        this.Age = Age;
    }

    public String getName() {
        return Name;
    }

    public void setName(String Name) {
        this.Name = Name;
    }

    public Integer getAge() {
        return Age;
    }

    public void setAge(Integer Age) {
        this.Age = Age;
    }

    // overriding toString() method
    @Override
    public String toString() {
        return "Customer{" + "Name=" + Name + ", Age=" + Age + '}';
    }

    static class CustomerSortingComparator implements Comparator<Student> {

        @Override
        public int compare(Student customer1, Student customer2) {

            // for comparison
            int NameCompare = customer1.getName().compareTo(customer2.getName());
            int AgeCompare = customer1.getAge().compareTo(customer2.getAge());

            // 2-level comparison using if-else block
            if (NameCompare == 0) {
                return ((AgeCompare == 0) ? NameCompare : AgeCompare);
            } else {
                return NameCompare;
            }
        }
    }

    public static void main(String[] args) {

        // create ArrayList to store Student
        List<Student> al = new ArrayList<>();

        // create customer objects using constructor initialization
        Student obj1 = new Student("Ajay", 27);
        Student obj2 = new Student("Sneha", 23);
        Student obj3 = new Student("Simran", 37);
        Student obj4 = new Student("Ajay", 22);
        Student obj5 = new Student("Ajay", 29);
        Student obj6 = new Student("Sneha", 22);

        // add customer objects to ArrayList
        al.add(obj1);
        al.add(obj2);
        al.add(obj3);
        al.add(obj4);
        al.add(obj5);
        al.add(obj6);

        // before Sorting arraylist: iterate using Iterator
        Iterator<Student> custIterator = al.iterator();

        System.out.println("Before Sorting:\n");
        while (custIterator.hasNext()) {
            System.out.println(custIterator.next());
        }

        // sorting using Collections.sort(al, comparator);
        Collections.sort(al, new CustomerSortingComparator());

        // after Sorting arraylist: iterate using enhanced for-loop
        System.out.println("\n\nAfter Sorting:\n");
        for (Student customer : al) {
            System.out.println(customer);
        }
    }
}