Switch statement loops through

Question

I'm trying to make a simple Menu with the switch statement. However i'm having a problem with the switch:

public class main {

    public static void main(String[] args) throws IOException {

         printMenu();

    }

    public static void printMenu() throws IOException{

    char selection = 0;
    do{
        System.out.println("Choose option: ");
        System.out.println("1. Option 1");
        System.out.println("2. Option 2");
        System.out.println("3. QUIT");
        System.out.println("\t\t\t");

        selection = (char)System.in.read();

        switch(selection){          
            case '1':

                    System.out.printf("opt1 chosen\n");

                break;

            case '2':

                System.out.printf("opt2 chosen\n");

                break;                  

            case '3':

                break;

            }
        }
        while(selection != '3'); 

    } 
}

For some reason, when selecting either one or two, the result is that print menu gets printed twice, like this:

Program output:

Choose option: 
1. opt1.
2. opt2.
3. opt3.

1
opt1 chosen
Choose option: 
1. opt1.
2. opt2.
3. opt3.

Choose option: 
1. opt1.
2. opt2.
3. opt3.

The question is, what causes this problem?

Answer 1

When you press a number and <Enter> this is two characters not one. i.e. you are typing

1\n

This is unavoidable, but you can chose to parse the input differently with Scanner which handles this differently, or you can ignore it. (or you can expect the user must type a \n after a number...

Answer 2

As Peter pointed out, the problem arises because of the way you are reading the 'selection' input. You can correct the functionality as follows:

public class main {

    public static void main(String[] args) throws IOException {
        printMenu();
    }

    public static void printMenu() throws IOException {
        char selection = '0';
        while (selection != '3') {
            if (selection != '\n') {
                System.out.println("Choose option: ");
                System.out.println("1. Option 1");
                System.out.println("2. Option 2");
                System.out.println("3. QUIT");
                System.out.println("\t\t\t");
            }
            selection = (char) System.in.read();
            switch (selection) {
                case '1':
                    System.out.printf("opt1 chosen\n");
                    break;
                case '2':
                    System.out.printf("opt2 chosen\n");
                    break;
                case '3':
                    break;
                default:
                    break;
            }
        }
    }
}