Write a Java application that accomplishes the following tasks.
1) Asks the number of homework assignment a student has submitted in a semester, and then the score in each of these assignments.
2) It then calculates the letter grade the student has earned, based on the average score of these assignments.
The program needs to have built in Exception handling for validating the input.
Assume that the full score for each assignment is 100. Student gets a 0 for each unsubmitted assignment.
Student's letter grade is based on the following scheme.
90 -- 100 A
80 -- 89 B
70 -- 79 C
60 -- 69 D
0 -- 60 F