java program is not able to read a string

Question

import java.util.*;

class DataTypes {

    public static void main(String args[]) {
        int i = 4;
        double d= 4.0;
        String s = "Hackerrank";
        Scanner scan = new Scanner(System.in);
        int j = scan.nextInt();
        double d1 = scan.nextDouble();
        String s1 = new String();
        s1 = scan.nextLine();
        j = j+i;
        System.out.println(j);
        d1 = d1+d;
        System.out.println(d1);
        System.out.println(s+" "+s1);
        scan.close();
    }
}

See the above code it is error free but after I input the double the program does not read the string it directly shows the output. But When I comment the scanning statements of int and double then the programs reads my string. Why is it so?

@foxdie value is already set to s not to s1. I want to print concatenated string of s and s1 by reading s1 from user. — Andy.inamdar, Dec 08 '17 at 08:50
@Andy.inamdar The `Scanner` allows you to input values in the console ...it serves you to verify that your result is correct or that a variable has good values. This is not a GUI that you can format... This is more an information. — F0XS, Dec 08 '17 at 08:59

Lalit Verma · Answer 1 · 2017-12-08T09:03:07.447

6

You are not reading the string as you want, just use below code to make it work as you want

s1 = scan.next();

For more information please see this link

EDIT :
If your input consist a string with spaces than you can do something like:

scan.nextLine();
s1 = scan.nextLine();

This is because of nextDouble(), this method does not consume the last newline character of your input, and thus that newline is consumed in the next call to nextLine(). Adding newLine() before reading String will consume the new Line and you will be able to input your String.

edited Dec 08 '17 at 09:03

answered Dec 08 '17 at 08:37

Lalit Verma

759
8
22

What if the input is "This is nextLine"? – Dorukhan Arslan Dec 08 '17 at 08:40
1

Yes. It's obvious. But the OP asks for scanning new "line", not first word. – Dorukhan Arslan Dec 08 '17 at 08:43
Better. Also, if you explain why "new String()" shouldn't be used, your answer will be complete. – Dorukhan Arslan Dec 08 '17 at 08:48
The provided link says nothing about what I mentioned. See the line "String s1 = new String();" in the question. – Dorukhan Arslan Dec 08 '17 at 08:54
@LalitVerma Thanks a lot. Its working. But why is it working now? why we need to use scan.nextLine() before s1 = scan.nextLine()? May I know the reason please? It will be helpful for me. :) – Andy.inamdar Dec 08 '17 at 08:57

score 0 · Answer 2 · answered Dec 08 '17 at 08:36

0

Change this line

s1 = scan.nextLine();

to

s1 = scan.next();

answered Dec 08 '17 at 08:36

Karan

448
4
9

but it does not take the space within strings – Andy.inamdar Dec 08 '17 at 08:43
try this `double d1 = Double.parseDouble(scan.nextLine());` – Karan Dec 08 '17 at 08:50

Amol Raje · Answer 3 · 2017-12-08T09:01:50.017

0

try this:

import java.util.*;
class Demo{
public static void main(String args[]){
  int i = 4;
  double d= 4.0;
  String s = "Hackerrank";
  Scanner scan = new Scanner(System.in);
  int j = scan.nextInt();
  double d1 = scan.nextDouble();
  String s1  = scan.next();
  j = j+i;
  System.out.println(j);
  d1 = d1+d;
  System.out.println(d1);
  System.out.println(s+" "+s1);
  scan.close();
 }
}

edited Dec 08 '17 at 09:01

answered Dec 08 '17 at 08:38

Amol Raje

772
2
7
16

Please format your code as it is hardly readable. You could also put some description instead of ready to use solution – Gaskoin Dec 08 '17 at 09:00

score 0 · Answer 4 · edited Dec 08 '17 at 08:49

0

Changing the line

 s1 = scan.nextLine();

to below line

 s1 = scan.next();

will work.

edited Dec 08 '17 at 08:49

Lalit Verma

759
8
22

answered Dec 08 '17 at 08:40

Abhishek

177
1
2
10

score 0 · Answer 5 · answered Dec 08 '17 at 08:41

this is because of you enters: , so till get new line it can not go to next line so for non string use example:

int j = scan.nextInt(); scan.nextLine();

import java.util.*;

class DataTypes {

    public static void main(String args[]) {

        int i = 4;
        double d = 4.0;
        String s = "Hackerrank";
        Scanner scan = new Scanner(System.in);

//      System.out.print("Enter j: ");
        int j = scan.nextInt();
        scan.nextLine();
//      System.out.print("Enter dl: ");
        double d1 = scan.nextDouble();
        scan.nextLine();

        String s1 = new String();
//      System.out.print("Enter s1: ");
        s1 = scan.nextLine();
        j = j + i;
        System.out.println(j);
        d1 = d1 + d;
        System.out.println(d1);
        System.out.println(s + " " + s1);
        scan.close();
    }
}

score 0 · Answer 6 · answered Dec 08 '17 at 08:49

0

Replace this lines as

double d1 = Double.parseDouble(scan.nextLine());

answered Dec 08 '17 at 08:49

Karan

448
4
9

score 0 · Answer 7 · answered Dec 08 '17 at 10:15

This problem is appearing because a call to nextDouble only consumes the number itself, and not only newlines after it.

This happens:

Your program asks the scanner for a new double
Your give the console 4 characters: 0.1\n
Scanner reads from the console, and gets 0.1\n
Since it now can calculate where the double ends, it pushes back \n to its buffer
Your program asks the scanner for a new newline
The scanner reads from its buffers: \n
Since it found a valid line ending, it returns the string in front of it without the trailing newline.

There are different solutions for this:

Prepend the string directly after the number in the input:

1 3.5I'm a short string

Consume the unneeded line character in your code manually:

        double d1 = scan.nextDouble();
        scan.nextLine();
        String s1 = scan.nextLine();

Call next instead of nextLine:

Notice, this will only consume 1 word at a time

        double d1 = scan.nextDouble();
        String s1 = scan.next();

Read the double using a call to nextline:

This will limit your program to newline separated numbers, instead of allowing any seperator:

int j = Integer.parseInteger(scan.nextLine());
double d1 = Double.parseDouble(scan.nextLine());
String s1 =scan.nextLine();

java program is not able to read a string

7 Answers7