This is a bad practice since you are changing the original Object:

public class valueReference{
    class Person{
      public int age;
      public Person(int years){
        age=years;
      }
    }
    public static void increment(int x) { x++; }

    public static void increment(Person p) { p.age++; }

  public static void main(String args[]){
    int a = 3;
    increment(a);
    System.out.println(a);//3
    Person pers = new Person(20);
    increment(pers)
    System.out.println(pers.age);//21
  }
}

i'm getting rusty :(

The Fibonacci sequence should be explained better

The instructions on how to calculate the fibonacci sequence are a little unclear. (n - 1) + (n - 2) appears to be some addition and subtraction. The calculation is really fib(n - 1) + fib(n - 2)

Timeout while doing test