Display the top two grades between students

I am taking a CSC class for java. This example has me stuck and honestly I cannot figure out what is wrong with my code even with the debugger. My question is specifically:

1. 
   

   How do I get my prompt to display and read multiple inputs only using Loops like Do-while, While, For. I am not allowed to use Arrays.

   
   


2. 
   

   Is my logic wrong?

   
   

Here is my code:

package assignment16;
import java.util.Scanner;

public class Exercise59 {

public static void main(String[] args) {
    Scanner input = new Scanner(System.in);

    System.out.print("Enter number of Students ");
    int numberOfStudents = input.nextInt();

    System.out.print("Enter students name");
    String name1 = input.nextLine();

    System.out.print("Enter student's grade");
    double grade1 = input.nextDouble();


    for (int i = 0; i < numberOfStudents; i++){

}


}

}