Nuances of the Scanner Class

Question

I'm having trouble with the Scanner class... here is a snippet of code from a program I am writing.
==========
1 System.out.print("Enter the name of the new passenger-> ");
2      String passengerName = scan.nextLine();
3      System.out.println(passengerName);
4      
5      System.out.print("Enter the ticket type (E or F)-> ");
6      String desiredClassType = scan.nextLine();
7      System.out.println(desiredClassType);
8      char desiredClassTypeCode = (desiredClassType.toUpperCase()).charAt(0);
9      
10
11      System.out.print("Enter the desired row-> ");
12      int desiredRow = scan.nextInt();
13      System.out.println(desiredRow);
14      
15      System.out.print("Enter the desired seat-> ");
16      String desiredSeat = scan.nextLine();
17      System.out.println(desiredSeat);
18      char desiredSeatCode = desiredSeat.charAt(0);
19      
20      System.out.print("Smoking or non-smoking (S or N)-> ");
21      String desiredSmoking = scan.nextLine();
22      System.out.println(desiredSmoking);
23      char desiredSmokingCode = (desiredSmoking.toUpperCase()).charAt(0);
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The problem is, after the scan.nextInt() on line 12, the user never gets a chance to enter input for the scan.nextLine() on line 16. The program just plows right on through and returns the following error at line 18:
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 0
If I change the scan.nextLine() in line 16 to scan.next(), it works alright until the next time I call a scan.nextLine at line 21. Then the same error message appears at line 23. Is there something I'm missing? I can't just change everything to scan.next because some inputs require a string that includes whitespace. However, scan.nextLine keeps giving me these errors...?

Answer 1

when the program asks you to enter a number, you enter a number and press enter. The nextInt method reads the number but leaves the line feed. Next, the program calls nextLine. What will it return? It will return the 0-length string from where the number ended until the line feed, and removes the line feed from the stream. This is why the user never gets a chance to enter anything: he's already entered what the program was looking for.
To get rid of the line feed, call nextLine directly after calling nextInt and throw away the return value.
int desiredRow = scan.nextInt();
scan.nextLine(); // throw away rest of line