How can I read input from the console using the Scanner class in Java?

Question

How could I read input from the console using the Scanner class? Something like this:

System.out.println(\"Enter your username: \");
Scanner = i         


        

Answer 1

Scanner scan = new Scanner(System.in);
String myLine = scan.nextLine();

Answer 2

You can use the Scanner class in Java

Scanner scan = new Scanner(System.in);
String s = scan.nextLine();
System.out.println("String: " + s);

Answer 3

A simple example:

import java.util.Scanner;

public class Example
{
    public static void main(String[] args)
    {
        int number1, number2, sum;

        Scanner input = new Scanner(System.in);

        System.out.println("Enter First multiple");
        number1 = input.nextInt();

        System.out.println("Enter second multiple");
        number2 = input.nextInt();

        sum = number1 * number2;

        System.out.printf("The product of both number is %d", sum);
    }
}

Answer 4

There is a simple way to read from the console.

Please find the below code:

import java.util.Scanner;

    public class ScannerDemo {

        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);

            // Reading of Integer
            int number = sc.nextInt();

            // Reading of String
            String str = sc.next();
        }
    }

For a detailed understanding, please refer to the below documents.

Doc

Now let's talk about the detailed understanding of the Scanner class working:

public Scanner(InputStream source) {
    this(new InputStreamReader(source), WHITESPACE_PATTERN);
}

This is the constructor for creating the Scanner instance.

Here we are passing the InputStream reference which is nothing but a System.In. Here it opens the InputStream Pipe for console input.

public InputStreamReader(InputStream in) {
    super(in);
    try {
        sd = StreamDecoder.forInputStreamReader(in, this, (String)null); // ## Check lock object
    }
    catch (UnsupportedEncodingException e) {
        // The default encoding should always be available
        throw new Error(e);
    }
}

By passing the System.in this code will opens the socket for reading from console.

Answer 5

When the user enters his/her username, check for valid entry also.

java.util.Scanner input = new java.util.Scanner(System.in);
String userName;
final int validLength = 6; // This is the valid length of an user name

System.out.print("Please enter the username: ");
userName = input.nextLine();

while(userName.length() < validLength) {

    // If the user enters less than validLength characters
    // ask for entering again
    System.out.println(
        "\nUsername needs to be " + validLength + " character long");

    System.out.print("\nPlease enter the username again: ");
    userName = input.nextLine();
}

System.out.println("Username is: " + userName);

Answer 6

1. To read input:

   Scanner scanner = new Scanner(System.in);
   String input = scanner.nextLine();
   

2. To read input when you call a method with some arguments/parameters:

   if (args.length != 2) {
       System.err.println("Utilizare: java Grep <fisier> <cuvant>");
       System.exit(1);
   }
   try {
       grep(args[0], args[1]);
   } catch (IOException e) {
       System.out.println(e.getMessage());
   }