.java中的结束程序使用字母“e”将字符串转换为int以退出程序

I have this grading program that I am trying a lot of things to exit the program using keyboard input, and in this case the letter "E". I created another method, but I couldn't make it to work together with the main method, and I am so new that I am just stuck. I tried using Boolean, and string to int conversion but all I get is errors. my code is below, thank you in advance, and anything helps I know that it might be a stupid question.I have this grading program that I am trying a