Question

create a Person class with two fields (name(String), age(int)) create all the required methods such as the accessors, mutators, toString(),constructors etc. Use the comparable interface and implement the compareTo method such that the person objects can be compared and sorted according to their age.

Answer 1

/* person.java */

import java.util.*;

class Person implements Comparator<Person>, Comparable<Person> {
private String name;
private int age;
Person() {
}

Person(String n, int a) {
name = n;
age = a;
}

public String getPersonName() {
return name;
}

public int getPersonAge() {
return age;
}

// Overriding the compareTo method
public int compareTo(Person d) {
return (this.name).compareTo(d.name);
}

// Overriding the compare method to sort the age
public int compare(Person d, Person d1) {
return d.age - d1.age;
}
}

public class Example {

public static void main(String args[]) {
// Takes a list o Dog objects
List<Person> list = new ArrayList<Person>();

list.add(new Person("Jack", 33));
list.add(new Person("Java", 32));
list.add(new Person("Buddy", 40));
list.add(new Person("Rob", 84));
list.add(new Person("Kevin", 21));
Collections.sort(list); // Sorts the array list

/* for(Person a: list) // printing the sorted list of names
System.out.print(a.getPersonName() + ", ");*/

// Sorts the array list using comparator
Collections.sort(list, new Person());
System.out.println(" ");
  
for(Person a: list) // printing the sorted list of ages
System.out.print(a.getPersonName() +" : "+ a.getPersonAge() + ", ");
}
}

Expected output

==============

Kevin : 21, Java : 32, Jack : 33, Buddy : 40, Rob : 84,

Please find attached screenshot

Kevin: 21, Java 32, Jack 33, Buddy 40, Rob : 84,