5.class_vs_instances.java

//https://www.hackerrank.com/challenges/30-class-vs-instance/problem
import java.io.*;
import java.util.*;

public class Person {
    private int age;	
  
	public Person(int initialAge) {
  		// Add some more code to run some checks on initialAge
         if(initialAge<0)
        {
            this.age=0;
            System.out.print("Age is not valid, setting age to 0.");
        }
        else
            this.age=initialAge;
          
	}

	public void amIOld() {
  		// Write code determining if this person's age is old and print the correct statement:
          System.out.println("");
            if(age>=0 && age < 13){
                 System.out.print("You are young.");}
            else if(age>=13 && age < 18){
                 System.out.print("You are a teenager.");}
            else{
                System.out.print("You are old.");}
            
	}

	public void yearPasses() {
  		// Increment this person's age.
          age=age+1;
	}

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int T = sc.nextInt();
		for (int i = 0; i < T; i++) {
			int age = sc.nextInt();
			Person p = new Person(age);
			p.amIOld();
			for (int j = 0; j < 3; j++) {
				p.yearPasses();
			}
			p.amIOld();
			System.out.println();
        }
		sc.close();
    }
}