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Thread: Query about Use of nextLine() method of Scanner class

  1. #1
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    Default Query about Use of nextLine() method of Scanner class

    My code is as follows:

    import java.util.Scanner;
    public class GetUserInput {
    public static void main (String args[]) {
    int i;
    float f ;
    String s;

    Scanner input = new Scanner (System.in);



    System.out.println ("enter an integer: ");
    i = input.nextInt();
    System.out.println ("you entered an integer equal to " + i);

    System.out.println ("enter a floating point number: ");
    f = input.nextFloat();
    System.out.println ("You entered a floating point number equal to " + f );

    System.out.println ("enter a sentence: ");
    s = input.nextLine();
    System.out.println ("You entered a sentence which is \" " +s+ " \" ");

    }
    }


    Output:

    D:\Java Codebase>javac GetUserInput.java

    D:\Java Codebase>java GetUserInput
    enter an integer:
    2
    you entered an integer equal to 2
    enter a floating point number:
    7
    You entered a floating point number equal to 7.0
    enter a sentence:
    You entered a sentence which is " "



    My Query is: input.nextLine() does not wait for user input. Instead it continues execution from next line. But if I move up input.nextLine(); before both input.nextInt(); and input.nextFloat() in the above code, the execution works fine, input.nextLine(); waits for user input. edited code and output are as follows.

    import java.util.Scanner;
    public class GetUserInput {
    public static void main (String args[]) {
    int i;
    float f ;
    String s;

    Scanner input = new Scanner (System.in);

    System.out.println ("enter a sentence: ");
    s = input.nextLine();
    System.out.println ("You entered a sentence which is \" " +s+ " \" ");

    System.out.println ("enter an integer: ");
    i = input.nextInt();
    System.out.println ("you entered an integer equal to " + i);

    System.out.println ("enter a floating point number: ");
    f = input.nextFloat();
    System.out.println ("You entered a floating point number equal to " + f );

    }
    }


    output:

    D:\Java Codebase>javac GetUserInput.java

    D:\Java Codebase>java GetUserInput
    enter a sentence:
    hi
    You entered a sentence which is " hi "
    enter an integer:
    1
    you entered an integer equal to 1
    enter a floating point number:
    8
    You entered a floating point number equal to 8.0


    Clarifications Invited.

    Thanks in advance,
    Satya
    Last edited by satyajit; April 10th, 2014 at 08:53 AM. Reason: Solved.


  2. #2
    Senior Member PhHein's Avatar
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    Default Re: Query about Use of nextLine() method of Scanner class

    When you enter a numeric value and use nextInt() you have entered an Integer and carriage return. nextInt reads the integer and the CR is still in the buffer. Now you call nextLine which reads the old CR form the buffer. Your first class will work if you insert input.next() before reading the sentence.

  3. #3
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    Default Re: Query about Use of nextLine() method of Scanner class

    Thanks PhHein! That clarified my doubt in every aspect, great explanation. :-)

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