Build failing on second iteration of loop in java

    boolean finished = false;
    while (!finished) {
    System.out.println("Enter 'a' (add), 'm' (multiply), 'h' for max value or 'q' (quit) <");

    char choice = scan.nextLine().charAt(0);

    if (choice == 'a') {
        System.out.println("Enter first operand value");
        int first = scan.nextInt();
        System.out.println("Enter second operand value");
        int second = scan.nextInt();
        System.out.println("Enter third operand value");
        int third = scan.nextInt();
        int m = add(first, second, third);
        finished=false;
     System.out.println(m);   
    }
    if (choice == 'm') {
        System.out.println("Enter first operand value");
        int first = scan.nextInt();
        System.out.println("Enter second operand value");
        int second = scan.nextInt();
        System.out.println("Enter third operand value");
        int third = scan.nextInt();
        int m = multiply(first, second, third);
        finished=false;
     System.out.println(m);   
    }
    if (choice == 'h') {
        System.out.println("Enter first operand value");
        int first = scan.nextInt();
        System.out.println("Enter second operand value");
        int second = scan.nextInt();
        System.out.println("Enter third operand value");
        int third = scan.nextInt();
        int m = max(first, second, third);
        finished=false;
     System.out.println(m);
    }
    if (choice =='q') {
        finished = true;

    }

I have this loop which word on the first iteration. However on the second iteration it fails. I get output like this:

Enter 'a' (add), 'm' (multiply), 'h' for max value or 'q' (quit) < a

Enter first operand value

5

Enter second operand value

5

Enter third operand value

5

15

Enter 'a' (add), 'm' (multiply), 'h' for max value or 'q' (quit) <

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 0 at java.lang.String.charAt(String.java:658)

Im new to java and I dont understand why its not working? Wouldn't the char choice variable reset each time the loop runs?