Build a java app that asks the user to input a series of grades between 0-100

Im extremely new at Java programming and my professor asked us to write a program that can:

Show each grade by the letter. (Ex: A, B, C, D, F) Show the Minimum & Average grade of the class Show the number of people who passed the exam (70+ is passing)

I have been trying to use arrays and if else statements to solve this but Im not making much progress. Can you guys please help me out?

I know I'm not good at coding, but here is something I am trying.

I also would like to incorporate if else statements in my code to make things simpler.

Thank you so much in advance.

import java.util.Scanner;

public class HelloWorld
{

  public static void main (String[] args)
  {
    double[] grades = new double[10];
    int sum

    Scanner scan = new Scanner (System.in);
    System.out.println ("Number of students: " + grades.length);

    for (int index = 0; index < grades.length; index++)
    {
      System.out.print ("Enter number " + (index+1) + ": ");
      grades[index] = scan.nextDouble();
    }
  }
}