What am I Doing wrong? Java

package generalPractice1;
/*
 * Practice Problem:
 *   - There are a ton of students and you need to determine what letter grade each student got depending on their
 *     percentage.
 *   - Print out how many of each letter grade there are using a count variable.
 *   - print each student's name along with their percentage and grade letter. One student per line.
 */

public class Main {
    public static void main(String[] args) {
        int[] grades = {30, 60, 85, 50, 90, 40, 90, 95, 99, 54};
        String[] students = {"Harry", "Josh", "Kyle", "Katelyn", "Tommy", "Jackson", "Jane", "Conner", "Paul", "Nancy"};


    }
    public static void checkGrades() {
        for (int i: grades) {
            System.out.println(i);

            if (i >= 90) {
                System.out.println("This user has an A!"); }
            else if (i >= 80) {
                System.out.println("This user has a B!"); }
            else if (i >= 70) {
                System.out.println("This user has a C!"); }

        }
    }
}