Java Comparable

Comparable: It is used to define the natural ordering of the objects within the class.--->method..compareTo()

Comparator:(TBD) It is used to define custom sorting logic externally.method..compare()

package collections;

public class mobile implements Comparable<Object> {
    String brand;
    int price;
    int ram;
    double weigth;

    mobile(String brand, int price, int ram, double weigth) {
        this.brand = brand;
        this.price = price;
        this.ram = ram;
        this.weigth = weigth;
    }

    public String toString() {
        return this.brand + " " + this.price + " " + this.ram + " " + this.weigth;

    }

    public int compareTo(Object o) // call compareTo as m1 and passes parameters as m2
    {
        // System.out.println("First "+ this.price);//m1(print and see how compare happen)
        mobile m = (mobile) o;// converting mobile class object
        // System.out.println("second "+ m.price);//m2(print and see how compare happen)
        if (this.price > m.price) {
            return 1;// ascending
        } else if (this.price < m.price) {
            return -1;// decending
        }
        return 0;//equal
    }

}

package collections;

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

public class mobshop {

    public static void main(String[] args) {
        mobile m1 = new mobile("samsang", 15000, 12, 5.0);
        mobile m2 = new mobile("vivo", 10000, 6, 7.0);
        mobile m3 = new mobile("apple", 100000, 4, 5.0);
        ArrayList al = new ArrayList();
        al.add(m1);
        al.add(m2);
        al.add(m3);

                System.out.println("Before Sorting: " + al);
        Collections.sort(al);// use to sort in order
        System.out.println("After Sorting: " + al);

        int max_price = 0;
        String brand = " ";
        Iterator it = al.iterator();
        while (it.hasNext()) {
            mobile mob = (mobile) it.next();
            if (mob.price > max_price) {
                max_price = mob.price;
                brand = mob.brand;
            }
        }
        System.out.println(max_price + " brand = " + brand);

    }

}

Output:
Before Sorting: [samsang 15000 12 5.0, vivo 10000 6 7.0, apple 100000 4 5.0]
After Sorting: [vivo 10000 6 7.0, samsang 15000 12 5.0, apple 100000 4 5.0]
100000 brand = apple

Reference:https://www.geeksforgeeks.org/comparable-vs-comparator-in-java/

package collections;

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

public class Battery {
public static void main(String[] args) {
    List<Mobile1> mobiles = new ArrayList<>();

    mobiles.add(new Mobile1("Samsung Galaxy S22", 4500, 8, 65000));
    mobiles.add(new Mobile1("iPhone 14", 3700, 6, 79000));
    mobiles.add(new Mobile1("OnePlus 10", 5000, 12, 55000));
    mobiles.add(new Mobile1("Redmi Note 12", 5000, 6, 18000));
    mobiles.add(new Mobile1("Realme X7", 4300, 8, 22000));
    mobiles.add(new Mobile1("Vivo V25", 4500, 8, 27000));
    mobiles.add(new Mobile1("Oppo Reno 8", 4500, 8, 32000));
    mobiles.add(new Mobile1("Poco F4", 4500, 8, 25000));
    mobiles.add(new Mobile1("Motorola Edge 30", 4020, 8, 28000));
    mobiles.add(new Mobile1("Asus ROG Phone 6", 6000, 16, 72000));

    Scanner sc =new Scanner(System.in);
    System.out.println("Choose sorting option:");
    System.out.println("1. Price (Ascending)");
    System.out.println("2. Battery (Descending)");
    System.out.println("3. RAM (Descending)");
    int ch=sc.nextInt();

    Mobile1.sortType = ch;

    Collections.sort( mobiles);
    for(Mobile1 b:mobiles)
    {
        System.out.println(b);
    }

}
}

package collections;

public class Mobile1 implements Comparable<Mobile1> {
    public static int sortType = 1;
    String name;
    int battery;
    int ram;
    double price;

    public String toString() {
        return name + " - Battery: " + battery + "mAh, RAM: " + ram + "GB, Price: ₹" + price;
    }

    public Mobile1(String name, int battery, int ram, double price) {
        super();
        this.name = name;
        this.battery = battery;
        this.ram = ram;
        this.price = price;
    }

    public int compareTo(Mobile1 other) {

        switch (sortType) {
        case 1:
            if (this.price > other.price) {
                return 1;
            } else if (this.price < other.price) {
                return -1;
            } else {
                return 0;
            }

        case 2: // Battery Descending
            if (this.battery > other.battery)
                return -1;
            else if (this.battery < other.battery)
                return 1;
            else {
                if (this.price > other.price) {
                    return 1;
                } else if (this.price < other.price) {
                    return -1;
                } else {
                    return 0;
                }
            }

        case 3: // RAM Descending
            if (this.ram > other.ram)
                return -1;
            else if (this.ram < other.ram)
                return 1;
            else
                return 0;

        default:
            return 0;
        }

    }

}

comparator

package Quantler;

public class Book {
String book;
String author;
Book(String book,String author)
{
    this.book=book;
    this.author=author;
}
}

package Quantler;

import java.util.Comparator;

public class Bookcompare implements Comparator<Book> {

    @Override
    public int compare(Book b1, Book b2) {

        return b1.book.compareTo(b2.book);
    }


}

package Quantler;

import java.util.ArrayList;
import java.util.Collections;

public class BookStorting {
    public static void main(String[] args) {
        ArrayList<Book> list=new ArrayList<>();
        list.add(new Book("java","neel"));
        list.add(new Book("python","sudhakar"));
        list.add(new Book("c","vimal"));
        Collections.sort(list,new Bookcompare());

        for(Book b:list)
        {
            System.out.println(b.book+" "+b.author);
        }

    }

}