Question

Java

I am stuck on, enter a number grade: 9.8 ERROR: 9.8 and enter a number grade: 10
ERROR: 10

Here is the specs
​​​​​​​
Write a class called Grades.

Grades must have a main method (see example of what the main method
does below).

Grades are values between zero and 10 (both zero and 10 included), and
are always rounded to the nearest half point (i.e. ALL GRADES entered
in the system end in either .0 or .5). To translate grades to letters:
8.5 to 10.0 become an "A," 7.5 and 8.0 become a "B," 6.5 and 7.0
become a "C," 5.5 and 6.0 become a "D," and 0.0 to 5.0 become an
"F."  Anything else is an error.

Implement a program such that, it asks the user for a grade, and then
it prints the corresponding letter. If the user enters a grade lower
than zero or higher than 10, print an error message (as in example
below). ALL GRADES MUST END IN EITHER .0 or .5, including 10.0 and
0.0.

% java Grades
enter a number grade: 11.0
ERROR: 11.0
% java Grades
enter a number grade: 11
ERROR: 11
% java Grades
enter a number grade: 10 
ERROR: 10
% java Grades
enter a number grade: 10.0
letter grade is A
% java Grades
enter a number grade: 9.8
ERROR: 9.8
% java Grades
enter a number grade: 9.5
letter grade is A
% java Grades
enter a number grade: 9.0
letter grade is A
% java Grades
enter a number grade: 9
ERROR: 9
% java Grades
enter a number grade: 8.5
letter grade is A
% java Grades
enter a number grade: 8.0
letter grade is B
% java Grades
enter a number grade: 7.5
letter grade is B
% java Grades
enter a number grade: 7.0
letter grade is C
% java Grades
enter a number grade: 6.0
letter grade is D
% java Grades
enter a number grade: 5.5
letter grade is D
% java Grades
enter a number grade: 5.0
letter grade is F
% java Grades
enter a number grade: 3.0
letter grade is F
% java Grades
enter a number grade: 0.0
letter grade is F
% java Grades
enter a number grade: 0
ERROR: 0
% java Grades
enter a number grade: -1
ERROR: -1
% java Grades
enter a number grade: 0.1
ERROR: 0.1
% java Grades
enter a number grade: 9.51
ERROR: 9.51
% java Grades
enter a number grade: 9.000001
ERROR: 9.000001
%

Answer 1

package proj;

import java.util.Date;
import java.util.Scanner;

public class Grade {

   public static void main(String[] args) {
       Scanner sc=new Scanner(System.in);
       System.out.print("enter a number grade:");
       String s=sc.next();
       if(!s.contains(".")){
           System.out.println("Error: "+s);
           return;
       }
       double grade=Double.parseDouble(s);
       double frac=(grade*10)%10; // to check whether grade entered end with .0 or .5 or not
       // (grade * 10) %10 it will return last digit of grade it that last digit is not either 5.0 or 0.0
       // then return error
       //ex grade =8.4 so 8.4*10=> 84.0=> 84%10 => 4 so this grade does not follow condition return erro
       if(frac!=0.0 && frac!=5.0) {
           System.out.println("Error: "+grade);
           return;
       }
       //else follow rules defined in question
       if(grade>=8.5 && grade<=10.0){
           System.out.println("letter grade is A");
       }
       else if(grade>=7.5 && grade<=8.0){
           System.out.println("letter grade is B");
       }
       else if(grade>=6.5 && grade<=7.0){
           System.out.println("letter grade is C");
       }
       else if(grade>=5.5 && grade<=6.0){
           System.out.println("letter grade is D");
       }
       else if(grade>=0.0 && grade<=5.0){
           System.out.println("letter grade is F");
       }
       else{
           System.out.println("Error: "+grade);

       }
   }

}

OUTPUT

enter a number grade:11.0
Error: 11.0
enter a number grade:11
Error: 11.0
enter a number grade:10
Error: 10
enter a number grade:10.0
letter grade is A
enter a number grade:9.8
Error: 9.8
enter a number grade:9.5
letter grade is A
enter a number grade:9.0
letter grade is A
enter a number grade:9
Error: 9
enter a number grade:8.5
letter grade is A
enter a number grade:8.0
letter grade is B
enter a number grade:7.5
letter grade is B
enter a number grade:0.0
letter grade is F
enter a number grade:-1
Error: -1

enter a number grade:9.51
Error: 9.51
enter a number grade:9.00001
Error: 9.00001