Program:

import java.util.Scanner;
public class Ch04PP05
{
	public static void main(String[] args)
	{
		Scanner console = new Scanner(System.in);
		
		int numberOfHomeworkAssignments;
		int pointsEarned;
		int pointsPossible;
		double totalPointsEarned = 0;
		double totalPointsPossible = 0;
		
		printStudentGradeScale();
		
		System.out.print("\nEnter the number of homework assignments: ");
		numberOfHomeworkAssignments = console.nextInt();
		
		for(int n = 1; n <= numberOfHomeworkAssignments; n++)
		{
			System.out.print("Enter the points possible in the homework assignment #" + n + ": ");
			pointsPossible = console.nextInt();
			totalPointsPossible += pointsPossible;
			
			System.out.print("Enter the points earned in the homework assignment #" + n + ": ");
			pointsEarned = console.nextInt();			
			totalPointsEarned += pointsEarned;			
		}
		
		System.out.print("\nEnter the points possible in the midterm exam: ");
		pointsPossible = console.nextInt();
		totalPointsPossible += pointsPossible;
		
		System.out.print("Enter the points earned in the midterm exam: ");
		pointsEarned = console.nextInt();		
		totalPointsEarned += pointsEarned;	
		
		System.out.print("\nEnter the points possible in the final exam: ");
		pointsPossible = console.nextInt();
		totalPointsPossible += pointsPossible;
		
		if(totalPointsEarned < totalPointsPossible * 0.90 && totalPointsPossible * 0.90 - totalPointsEarned <= pointsPossible)
		{
			System.out.println("The student needs to get at least " 
					+ (totalPointsPossible * 0.90 - totalPointsEarned) + " score in the final exam to get the A grade.");
		}
		
		if(totalPointsEarned < totalPointsPossible * 0.80 && totalPointsPossible * 0.80 - totalPointsEarned <= pointsPossible)
		{
			System.out.println("The student needs to get at least " 
					+ (totalPointsPossible * 0.80 - totalPointsEarned) + " score in the final exam to get the B grade.");
		}
		
		if(totalPointsEarned < totalPointsPossible * 0.70 && totalPointsPossible * 0.70 - totalPointsEarned <= pointsPossible)
		{
			System.out.println("The student needs to get at least " 
					+ (totalPointsPossible * 0.70 - totalPointsEarned) + " score in the final exam to get the C grade.");
		}
		
		if(totalPointsEarned < totalPointsPossible * 0.60 && totalPointsPossible * 0.60 - totalPointsEarned <= pointsPossible)
		{
			System.out.println("The student needs to get at least " 
					+ (totalPointsPossible * 0.60 - totalPointsEarned) + " score in the final exam to get the D grade.");
		}
		
		System.out.print("Enter the points earned in the final exam: ");
		pointsEarned = console.nextInt();		
		totalPointsEarned += pointsEarned;			
		
		
		System.out.println("\nTotal points possible: " + totalPointsPossible);	
		System.out.println("Total points earned: " + totalPointsEarned);
		System.out.println("Student's grade in the course: " + getCourseGrade(totalPointsPossible, totalPointsEarned));		
		
	}

	public static void printStudentGradeScale()
	{
		System.out.println("Student's grade scale:");
		System.out.println("------------------------");
		System.out.printf("%-5s%18s\n", "GRADE", "SCALE");
		System.out.println("------------------------");
		System.out.printf("%3s%20s\n", "A", "for >= 90%");
		System.out.printf("%3s%20s\n", "B", "for >= 80%");
		System.out.printf("%3s%20s\n", "C", "for >= 70%");
		System.out.printf("%3s%20s\n", "D", "for >= 60%");
		System.out.printf("%3s%20s\n", "F", "for <  60%");
		System.out.println("------------------------");		
	}
	
	public static String getCourseGrade(double totalPointsPossible, double totalPointsEarned)
	{
		if(totalPointsEarned / totalPointsPossible * 100 >= 90)
		{
			return "A";
		}
		else if(totalPointsEarned / totalPointsPossible * 100 >= 80)
		{
			return "B";
		}
		else if(totalPointsEarned / totalPointsPossible * 100 >= 70)
		{
			return "C";
		}
		else if(totalPointsEarned / totalPointsPossible * 100 >= 60)
		{
			return "D";
		}
		else
		{
			return "F";
		}
	}
}

Output:

Student's grade scale:
------------------------
GRADE             SCALE
------------------------
  A          for >= 90%
  B          for >= 80%
  C          for >= 70%
  D          for >= 60%
  F          for <  60%
------------------------

Enter the number of homework assignments: 3
Enter the points possible in the homework assignment #1: 20
Enter the points earned in the homework assignment #1: 15
Enter the points possible in the homework assignment #2: 20
Enter the points earned in the homework assignment #2: 16
Enter the points possible in the homework assignment #3: 20
Enter the points earned in the homework assignment #3: 17

Enter the points possible in the midterm exam: 40
Enter the points earned in the midterm exam: 30

Enter the points possible in the final exam: 100
The student needs to get at least 82.0 score in the final exam to get the B grade.
The student needs to get at least 62.0 score in the final exam to get the C grade.
The student needs to get at least 42.0 score in the final exam to get the D grade.
Enter the points earned in the final exam: 80

Total points possible: 200.0
Total points earned: 158.0
Student's grade in the course: C