While loop with case - getting error

[jmanv888]

I am trying to write a program that will ask the user how many classes they had for a semester. It proceeds to present the user with 5 options for the grade they received A,B,C,D,F. What I am trying to do is a while loop that counts down while the user inputs his grades for the number of classes he/she took that semester. I am able to compile the code but when I type in how many classes in the semester I receive the error " Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out o range: 0 at java.land.String.CharAt<Unknown Source> at GPA.main<GPA.java:38> Any help would be awesome and it is deeply appreciated.

Thank you,
Jason

import java.util.Scanner;

public class GPA {
    public static void main(String[] args) {

	Scanner input = new Scanner(System.in);  

	int CounterNew=0;  
	
	
	int CountA=0;
	int CountB=0;
	int CountC=0;
	int CountD=0;
	int CountF=0;
	
	System.out.println("Enter how many classes you took: ");
	int Counter = input.nextInt();


        
	System.out.println("\n\nEnter the grade you recieved from the list: ");
	System.out.println("A");
	System.out.println("B");
	System.out.println("C");
	System.out.println("D");
	System.out.println("F");



	
	String choice = input.nextLine();
	char ch = choice.charAt(0); 
        
	while (Counter > 0){
	switch (ch)

	{
	case 'A': 
	case 'a': 
	System.out.println("A = 4.0");
        CountA++;
	break;

	case 'B': 
	case 'b':
	System.out.println("B = 3.0");
        CountB++;
	break;

	case 'C': 
	case 'c':
	System.out.println("C = 2.0");
        CountC++;
	break;

	case 'D': 
	case 'd':
	System.out.println("D = 1.0");
        CountD++;
	break;

	case 'F': 
	case 'f':
	System.out.println("F = 0.0");
        CountF++;
	break;

	default:
	System.out.println("Hey dummy, enter only a A, B, C, D, or F!");
        }
        
	{
		Counter--;
		CounterNew++;
	}	
        }
	{
		System.out.println("Your average is: " +  "%");
	}
   }
}

[makpandian]

Dude

Its because you have entered empty string from keyboard.. Make sure what string you have typed by SOP.

[Junky]

You have fallen foul of the Scanner.nextInt problem. If user enters 48<enter> then the nextInt method only reads the 48 and leaves the carriage return in the buffer. No what you have to remember is that there is a String between the 8 and the carriage return, it just happens to be an empty String or a String with a length of 0. So when you call nextLine it returns that empty String to your choice variable. Of course then trying to extract the char at position 0 will throw the exception becuase it does not exist.

Quick and dirty solution call nextLine and throw it away immediately after the call to nextInt.

[Junky]

Dude

Its because you have entered empty string from keyboard.. Make sure what string you have typed by SOP.

No it isn't.