Day 4: Class vs. Instance Hackerrank Solution java Do Check My Video For Explnation: Sample Input 4 -1 10 16 18 Sample Output Age is not valid, setting age to 0. You are young. You are young. You are young. You are a teenager. You are a teenager. You are old. You are old. You are old. Code: 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 ){ age = 0 ; System.out.prin...