Trying to produce error message

Question

Hi
Im fairly new to Java programming and am in the middle of completing a small assignment.
I'm trying to get the program to produce an error message after it asks a user to "Press 'Q' to Quit or 'P' to Print". Although the prog doesn't carry on if any other keys are pressed it doesnt actually produce an error message but thats what i want it to do.
Can someone please help!
public void display(){
  String printQuitResponse;
  int printBook;
  try {
   do {
    int bookChoice = 0;
    System.out.println("\nPress 'Q' to Quit or 'P' to Print details of a book.");
    printQuitResponse = reader.readLine();
      if (printQuitResponse.equalsIgnoreCase("P")) {
        System.out.println(
            "\nWhich book would you like to see the details of (1, 2, 3)");
        try {
          bookChoice = Integer.parseInt(reader.readLine());
        } catch (IOException ioe) {
        } catch (NumberFormatException nfe) {
          System.out.println("Invalid entry, please try again.");
         if (bookChoice == 1 || bookChoice == 2 || bookChoice == 3){
           System.out.println("\nTitle: " + title[bookChoice-1] +
                              "\nAuthor: " + author[bookChoice-1] +
                              "\nShelf Location: " + sLocation[bookChoice-1]);
           if (availability[bookChoice-1] == true) {
             System.out.println("Available: Yes");
           else if (availability[bookChoice-1] == false) {
            System.out.println("Available: No");
   }while (!printQuitResponse.equalsIgnoreCase("Q"));
   catch (IOException ioe) {
      System.out.println("Invalid entry, please try again");
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Answer 1

printQuitResponse = reader.readLine();you are waiting for any key followed by a "\r" | "\n" | "\r\n"
i.e. your program never leaves the readLine as long as the user
does not type <AnyKey><ENTER>