Read input line by line

Question

How do I read input line by line in Java? I searched and so far I have this:

import java.util.Scanner;

public class MatrixReader {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        while (input.hasNext()) {
            System.out.print(input.nextLine());
        }
    }

The problem with this is that it doesn't read the last line. So if I input

 10 5 4 20
 11 6 55 3
 9 33 27 16

its output will only be

10 5 4 20 11 6 55 3

Works fine for me using your exact code. Don't forget to press enter. — FThompson, Aug 07 '12 at 08:37
I think you have copied than pasted all input variable at once — Ahmet Karakaya, Aug 07 '12 at 08:40

score 16 · Accepted Answer · edited May 23 '17 at 11:46

16

Ideally you should add a final println() because by default System.out uses a PrintStream that only flushes when a newline is sent. See When/why to call System.out.flush() in Java

while (input.hasNext()) {
    System.out.print(input.nextLine());
}
System.out.println();

Although there are possible other reasons for your issue.

edited May 23 '17 at 11:46

Community

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1

answered Aug 07 '12 at 08:41

Dan Gravell

7,049
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how the hell does this answer answer the question?? – Bohdan Jan 16 '18 at 17:55
@Bohdan the answer is in the comments under the question. The OP just forgot to press enter after the last line, so it was not processed by the program. I guess he just accepted the most-upvoted answer after he realised he was "dumb" (his words not mine) for not pressing enter – Adam Burley Jan 26 '21 at 09:53

score 3 · Answer 2 · answered Jul 16 '14 at 03:05

The previously posted suggestions have typo (hasNextLine spelling) and new line printing (println needed each line) issues. Below is the corrected version --

import java.util.Scanner;

public class XXXX {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        while (input.hasNextLine()){
            System.out.println(input.nextLine());
        }
    }
}

score 1 · Answer 3 · answered Aug 07 '12 at 08:57

1

Try using hasnextLine() method.

while (input.hasnextLine()){


    System.out.print(input.nextLine());


 }

answered Aug 07 '12 at 08:57

Kumar Vivek Mitra

32,278
6
43
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Read input line by line

3 Answers3

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