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Sergio AG
Asked: 2020-05-29 12:11:34 +0800 CST 2020-05-29 12:11:34 +0800 CST

Doubt Scanner class in Java

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I have this little code. It happens that when the time comes to enter the third data (the name), it skips it, it is as if it automatically hit enter and could not write anything:

        Scanner sc = new Scanner(System.in);
        System.out.println("Introduce el primer numero: ");
        int num1 = sc.nextInt();
        System.out.println("Introduce el segundo numero: ");
        int num2 = sc.nextInt();
        System.out.println("Introduce tu nombre: ");
        String nombre = sc.nextLine();
        System.out.println("--------------"); //esto no es mas que decoracion

In such a way that the console output would be something like this:

Introduce el primer numero:    
1
Introduce el segundo numero:    
2
Introduce tu nombre:
-------------

I don't know why this happens. It's like the Scanner class goes crazy when I first ask it for int and then for String. Do you know what happens?

java

2 Answers

  1. Best Answer

    This is because the method Scanner.nextIntdoes not consume the last newline character of its input, and therefore that newline is consumed on the next call to Scanner.nextLine.

    You will find the same behavior when you use Scanner.nextLineafter Scanner.next ()or any other method Scanner.nextFoo(except nextLine).

    What you can do is the following:

    Scanner sc = new Scanner(System.in);
System.out.println("Introduce el primer numero: ");
int num1 = sc.nextInt();
System.out.println("Introduce el segundo numero: ");
int num2 = sc.nextInt();
//Se consume la siguiente linea
sc.nextLine();
System.out.println("Introduce tu nombre: ");
String nombre = sc.nextLine();
System.out.println("--------------");

    Font:

    https://stackoverflow.com/questions/13102045/scanner-is-skipping-nextline-after-using-next-or-nextfoo

    • 1

  2. Just change the

    String nombre = sc.nextLine();

    by

    String nombre = sc.next();

    For some reason the nextLine() doesn't let you enter such an input.

    In case you have doubts about the differences>

    next() reads until it finds a space (stops reading at the first space)

    nextLine() reads the entire line (stops reading at line break)

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