Cant detect if enter key got pressed after System.out.print() java

Question

I am a beginner in java. The task is to enter a books name and age recommendation. When pressing enter the program should no longer take input. The program just takes input for one book. Why is this the case?

Scanner scanner = new Scanner(System.in);
        ArrayList<Book> bookList = new ArrayList(); 
        
        while(true){
                     
            System.out.print("Input the name of the book, empty stops: "); //Only one input possible
            String line = scanner.nextLine();
            if(line.equals("")){
                break;
            }
            
            System.out.print("Input the age recommendation: ");
            int line2 = scanner.nextInt();
            
            Book book = new Book(line, line2);
            bookList.add(book);
            
        }

score 0 · Answer 1 · answered Apr 05 '21 at 03:52

0

If you want to break on enter, use this:

if(line.equals(System.lineSeparator()) { break; }

answered Apr 05 '21 at 03:52

Rafay

80
8

Have you tried if that actually works? – Tom Apr 05 '21 at 05:14

score 0 · Answer 2 · answered Apr 05 '21 at 03:56

It's breaking after the first line because scanner.nextInt(); only reads the number, but the newLine created because of you pressing enter to enter the age was not. So the loop continues and then it gets processed on the next loop as an empty string. To solve it you could do:

    Book book = new Book(line, line2);
    bookList.add(book);
     
    if (scanner.hasNextLine())
    scanner.nextLine();

score -1 · Accepted Answer · answered Apr 05 '21 at 03:59

-1

This is why it happened. https://www.geeksforgeeks.org/why-is-scanner-skipping-nextline-after-use-of-other-next-functions/ Using int line2 = Integer.parseInt(scanner.nextLine()); can solve your problem

answered Apr 05 '21 at 03:59

judaikun88

59
5

Cant detect if enter key got pressed after System.out.print() java

3 Answers3