Driver Exam multiple choice Array while loop prompt student Answers method

Question

Looking for some help here. I'm trying to make this method work. Whenever I run the method, it throws IllegalArgumentException even if I do type in A,B,C or D. I am using an inputReader class. Here is the code for my DriverExam class. Please let me know where I am going wrong. I'd like it so the only valid answers are a,b,c,or d. I have to use a while loop and everything I've tried won't help me match the driverAnswers.

public class DriverExam
{
    // instance variables
    public static final String[] ANSWERS = {"B","D","A","A","C","A","B","A","C","D","B","C","D","A","D","C","C","B","D","A"};

    private String [] driverAnswers;
    private InputReader inputReader;

    public DriverExam(){
        driverAnswers = new String[20];
        inputReader = new InputReader();
    }

    public void promptStudentAnswers(){
        int index = 0;

        while(index < driverAnswers.length){
            System.out.println("enter answer");
            String driverAnswers = inputReader.readString();
            if(driverAnswers != ANSWERS[index]){
                throw new IllegalArgumentException(" answers can only be A,B,C or D");
            } else{ 
                index++;
            }
        }
    }
}

Answer 1

First, you want to test if the answer is one of A, B, C or D (not that the answer matches something in the correct answers array). Also, your driverAnswers is masked because you created another local variable with that name. Basically, I think you wanted something like

public void promptStudentAnswers() {
    int index = 0;

    while (index < driverAnswers.length) {
        System.out.println("enter answer");
        String answer = inputReader.readString().trim().toUpperCase();
        if (answer.length() == 1 && "ABCD".indexOf(answer) != -1) {
            driverAnswers[index] = answer;
            index++;
        } else {
            System.out.println("Answers can only be A,B,C or D");
        }
    }
}