Skipping An Input line in java

Question

So I have an addItem() method where I can add a book, tape, or cd object to my inventory. To store the book, tape, or cd object, I obtain the title, author, and price of the object from the user. HOWEVER, when I run the program, it skips the "please enter the title: " and goes right to "please enter the author:". Then when I have it show the information, the title field is 'null'.

static void addItem(int type) {     

    String title;
    String author;
    Double price;

    System.out.println("Please enter the title");
    title = keyboard.nextLine()

    System.out.println("Please enter the author");
    author = keyboard.nextLine();

    System.out.println("Please enter the price");
    price = keyboard.nextDouble();


        if(type == 0){
            Book BookStoreItem;

                BookStoreItem = new Book(title, author, price);

            System.out.println("You've entered:");
            System.out.println("Title: " + BookStoreItem.getTitle());
            System.out.println("Author: " + BookStoreItem.getAuthor());
            System.out.println("Price: " + BookStoreItem.getPrice());
        }

        if(type == 1){
            Tape BookStoreItem;

            BookStoreItem = new Tape(title, author, price);

            System.out.println("You've entered:");
            System.out.println("Title: " + BookStoreItem.getTitle());
            System.out.println("Author: " + BookStoreItem.getAuthor());
            System.out.println("Price: " + BookStoreItem.getPrice());
        }

        if(type == 2){                  
            CD BookStoreItem;

            BookStoreItem = new CD(title, author, price);

            System.out.println("You've entered:");
            System.out.println("Title: " + BookStoreItem.getTitle());
            System.out.println("Author: " + BookStoreItem.getAuthor());
            System.out.println("Price: " + BookStoreItem.getPrice());
        }


}//end of addItem()

Here is a sample output:

Press:
    0    To add a book to the inventory
    1    To add a tape to the inventory
    2    To add a Cd to the inventory
Please enter your choice: 0
Please enter the title:
Please enter the author: John Smith
Please enter the price: 55.50

Title: null
Author: John Smith
Price: 55.5

Here's an update with the menu on it:

static void printMenu() {
    System.out.println("\nPress:");
    System.out.println("\t" + ADD_BOOK + "\tTo add a book to the inventory\n");
    System.out.println("\t" + ADD_TAPE + "\tTo add a tape to the inventory\n");
    System.out.println("\t" + ADD_CD + "\tTo add a CD to the inventory\n");
    System.out.println("\t" + SHOW_ITEM_LIST + "\tTo display a list of available books\n");
    System.out.println("\t" + SEARCH_ITEM + "\tTo search for a specific book\n");
    System.out.println("\t" + QUIT + "\tTo exit\n");
}

and with the choices:

static void runBookStoreApplication() {
    int userChoice = QUIT;
    String quitMessage = "\nThank you for using the BookStoreApplication!";
    String invalidOptionMessage = "\nInvalid option!"; 

    do{
        printMenu();
        userChoice = getUserChoice();

        switch (userChoice) {
            case ADD_BOOK:
                addItem(0);
                break;
            case ADD_TAPE:
                addItem(1);
            case ADD_CD:
                addItem(2);
            case SHOW_ITEM_LIST:
                showItemList();
                break;
            case SEARCH_ITEM:
                searchItem();
                break;
            case QUIT:
                System.out.println(quitMessage);
                break;
            default:
                System.out.println(invalidOptionMessage);
        }
    } while(userChoice != QUIT);

}//end of runBookStoreApplication

with getUserChoice:

static int getUserChoice() {
    int choice;

    System.out.print("Please enter your choice: ");
    choice = keyboard.nextInt();

    return choice;
}

Answer 1

You didn't show us the code where you ask "Please enter your choice:", but I bet that you are using keyboard.nextInt() or something. This method does not consume all the line, just the integer 0, so when you call nextLine() afterwards it actually returns immediately with the rest of the line (that is, with an empty string).

To solve this, call keyboard.nextLine() before your method.

Edit:

now that you have put your getUserChoice() method, you can see that there is a call to keyboard.nextInt(), as I presumed. Just call nextLine() after it so you consume all the line and the scanner is ready for your next input:

static int getUserChoice() {
    int choice;

    System.out.print("Please enter your choice: ");
    choice = keyboard.nextInt(); // consume just the integer

    // consume the rest of the line
    keyboard.nextLine();

    return choice;
}