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Neelakandan R
Neelakandan R

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Java Comparable

#java #beginners #fullstack #payilagam

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 } }
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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); } }
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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); } } }
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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; } } }
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comparator

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