รบกวนผู้รู้ช่วยแก้โจทย์ Java นี้หน่อยครับ If else มันไม่รัน

ของผมทำไว้เอาไปปรับเปลียนให้มันเข้ากับโจทรย์เอา

import java.util.*;
class sic01{
    public static void main (String [ ] args){
      Scanner Sc = new Scanner(System.in);
      //String name = Sc.nextLine();
      //System.out.println("..."+name+"...");
      System.out.print("number fo students : ");
      int a = 0;
      char man;
      a = Sc.nextInt();    
      while(a<=0){
          System.out.print("new nuber fo students");
          a = Sc.nextInt();
      }
      float n[ ] = new float[a];
        for(int i = 0; i<n.length; i++){
            System.out.print("student "+(i+1)+ " : ");
              n[ i ] = Sc.nextFloat();
              while (n[ i ]>100){
                  System.out.print("new student "+(i+1)+" : ");
                  n[ i ] = Sc.nextFloat();
              }
              if(n[ i ]>=90.0){
                  man = 'A';
              }else if(n[ i ]>=80.0){
                  man = 'B';
              }else if(n[ i ]>=70.0){
                  man = 'C';
              }else if(n[ i ]>=60.0){
                  man = 'D';
              }else{
                  man = 'F';
              }
              System.out.println("You grade : "+man);
        }
    }
}