Problems with Scanner.nextLine in Java

Question

In Java, I have tried

try (Scanner sc = new Scanner(System.in)) {
    while (sc.hasNextLine()) {
        System.out.print("Name: ");
        String name = sc.nextLine();
        System.out.println("Name is \"" + name + "\"");
    }
}

but it doesn't output Name: before asking for the input.

The console just shows an empty console window in which I can input the name.

How can I make sure Name: is outputted before asking for the name?

Edit

try (Scanner sc = new Scanner(System.in)) {
    System.out.print("Name: ");

    while (sc.hasNextLine()) {
        String name = sc.nextLine();
        System.out.println("Name is \"" + name + "\"");

        System.out.print("Age: ");
        int age = sc.nextInt();
        System.out.println("Age is " + age);

        System.out.print("Name: ");
    }

You're right - flushing wasn't it. The `while( ..hasNextLine() )` is waiting for input, which is why it doesn't print.. — Kenney, Feb 04 '16 at 02:44

10 Replies · Accepted Answer · 2016-02-04T02:49:31.530

0

Put your println before the while loop and then add one at the end.

try (Scanner sc = new Scanner(System.in)) {
    System.out.print("Name: ");        
    while (sc.hasNextLine()) {

        String name = sc.nextLine();
        System.out.println("Name is \"" + name + "\"");
        System.out.print("Name: ");
    }
}

The scanner waits until it receives input before it runs the next code so just put the print before the scanner and then at the end of the while loop.

edited Feb 04 '16 at 02:49

answered Feb 04 '16 at 02:34

10 Replies

426
9
25

But it's a loop, so I want to print the name every time the loop is run – Jamgreen Feb 04 '16 at 02:38
It does, try to run it. – 10 Replies Feb 04 '16 at 02:38
You can see that it prints before the scanner, and then once its been scanned it prints it again. – 10 Replies Feb 04 '16 at 02:39
You should also explain why it didn't work properly for the OP originally... Basically, `Scanner#hasNextLine()` waits for some input if the stream is still open... So, it won't enter the loop until you input something... – Codebender Feb 04 '16 at 02:41
Ah I see. But what about the code in my edit? It doesn't work behave correctly on second iteration – Jamgreen Feb 04 '16 at 02:44
@Jamgreen What doesn't work on the second iteration? – 10 Replies Feb 04 '16 at 02:47
@Jamgreen, see my edit for explanation to your edit :p – Roy Wang Feb 04 '16 at 02:51

score 0 · Answer 2 · edited May 23 '17 at 12:24

0

You should put System.out.print("Name: "); before of the while loop like this:

  try (Scanner sc = new Scanner(System.in)) {
        System.out.print("Name: ");
        while (sc.hasNextLine()) {
            String name = sc.nextLine();
            System.out.println("Name is \"" + name + "\"");
        }
    }

If you want to know the cause of this issue take a look at this link1 and link2

edited May 23 '17 at 12:24

Community

1
1

answered Feb 04 '16 at 02:34

Abdelhak

8,299
4
22
36

If you have the same answer as me, you don't need to post another. – 10 Replies Feb 04 '16 at 02:38
@10Replies I think that but where is the problem i answered without see your answer – Abdelhak Feb 04 '16 at 02:41

Roy Wang · Answer 3 · 2016-02-04T02:49:06.720

This might be a better design to avoid duplicated code. Don't have to restrict the loop end condition to the while statement ;)

    try (Scanner sc = new Scanner(System.in)) {
        while (true) {
            System.out.print("Name: ");
            if (!sc.hasNextLine()) break;
            String name = sc.nextLine();
            System.out.println("Name is \"" + name + "\"");
        }
    }

EDIT: Your edit does not work correctly because sc.nextInt() is not eating the line feed, so put sc.nextLine() after the sc.nextInt().

Problems with Scanner.nextLine in Java

Edit

3 Answers3