[JAVA] ArrayList를 사용하여 학점 구하기

package Ex01;

import java.util.ArrayList;
import java.util.Scanner;

public class ArrayListEx2 {
	public static void main(String[] args) {
		ArrayList<Character> gradeList = new ArrayList<Character>();
		Scanner scanner = new Scanner(System.in); 
		double avg = 0.0;

		System.out.print("6개의 학점을 빈 칸으로 분리 입력(A/B/C/D/F)>>");
		for(int i=0; i<6; i++) {
			String grade = scanner.next(); 
			if(grade.length() > 1) {
				System.out.println("학점을 잘못 입력 하셨습니다.");
				scanner.close();
				return;
			}
			char ch = grade.charAt(0);
			if((ch >='A' && ch <='D') || ch=='F') {
				gradeList.add(ch);
			}else {
				System.out.println("잘못 입력");
				scanner.close();
				return;
			}
		}
		
		for(int j=0; j<gradeList.size(); j++) {
			char ch = gradeList.get(j);
			switch (ch) {
			case 'A': avg = avg + 4.0;
				break;
			case 'B': avg = avg + 3.0;
				break;
			case 'C': avg = avg + 2.0;
				break;
			case 'D': avg = avg + 1.0;
				break;
			case 'F': avg = avg + 0.0;
				break;
			}
		}
		
		avg /= gradeList.size();
		System.out.println(avg);		
	}
}