JAVA Programming : Using Scanner for User Input

JAVA Scanner 

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As we now know a little bit about Java programming we will start making our first program.  In this tutorial we learn how to get input from user. There are a number of ways for taking input form user in Java and one way is using Scanner. A Scanner class is already built in Java and present in the java.util package. A scanner takes input from various types of Input Streams.

Creating a Scanner Object:
Lets create a scanner object that accepts systems.in as input stream it means that scanner will take input from console. 

Scanner scan = new Scanner(System.in);  // System.in is an InputStream

A scanner can take various types as input stream for example, here we have a File Reader as input stream that reads data from a file named as MyFile.

Scanner scanfile = new Scanner(new FileReader("MyFile"));

Getting User Input form Console using Scanner : Lets create a class that take two integer input from user and prints their sum. To use the Scanner class, first we need to import it. Take a look at the code :

import java.util.Scanner; public class UserInput {   public static void main(String args[]){       int second ;     int first;     int total;     Scanner scan = new Scanner(System.in);     System.out.println("enter 1st no.");     first = scan.nextInt(); //stores user input into first               System.out.println("enter 2nd no.");     second = scan.nextInt(); //stores user input into second     total = first + second ;  //sum of first and second       System.out.println("sum = "+ total);    } }

In the first line of code, we have an import statement to import Scanner class. Now we can use the Scanner class anywhere in our code. In our class we have three int variables first, second and total. Variable first and second will hold the user input and total will hold their sum.

To take integer input scanner has a method called nextInt. This methods reads the integer input by user. In the above code we have used this method two times and to save user input in int variables first and second.

Output of Program :

Note that if are using nextInt method and the input given is not integer, then compiler will give an error. There are some other methods that are used for different types of input.

Method	Reads
int nextInt()	Reads the next input as an int. If the input is not an integer,InputMismatchException is thrown.
long nextLong()	Reads the next token as a long. If the next token is not an long,InputMismatchException is thrown.
float nextFloat()	Reads the next input as a float. If the input is not a float, InputMismatchException is thrown.
double nextDouble()	Reads the next input as a double. If the input is not a double, InputMismatchException is thrown.
String next()	Finds and returns the next complete token from this scanner and returns it as a string; a token is usually ended by whitespace such as a blank or line break.
String nextLine()	Reads the rest of the current line, excluding any line separator at the end.
void close()	Closes the scanner.