Java Scanner Class Tutorial

Scanner Class  in Java

 

In this tutorial, we are going to learn about Scanner class in Java.  It allows us to read data from various sources such as using keyboard, file, string. This tutorial explains  you,  how to read data from various sources using scanner class. There are different methods available to read different types of data. You will find a list of methods provided in Scanner class  and how to use them. 

  

 

Table of Contents

1.  Reading Data from Keyboard - System.in
2.  Reading Data from File
3.  Reading Data from  String 
1.  ReadingString Delimiter 
   

 

1.    Reading Data from Keyboard - System.in

import java.util.Scanner; // import the Scanner class

class Main {

  public static void main(String[] args) {
    Scanner input= new Scanner(System.in);
    
    // String Input
    System.out.println("Enter Name");
    String name = input.nextLine();

    // Numerical Input

    System.out.println("Enter Age");
    int age = input.nextInt(); 

    System.out.println("Enter Salary");
    double salary = input.nextDouble();

    // Output input by user
    System.out.println("Name: " + name);
    System.out.println("Age: " + age);
    System.out.println("Salary: " + salary);
}
}

Output:

C:\javademo>java Main
Enter Name

John
Enter Age
23
Enter Salary
23000
Name: John
Age: 23
Salary: 23000.0

C:\javademo>

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2.    Reading Data from - File

import java.util.Scanner;

import java.io.File;
import java.io.FileNotFoundException;



public class JavaScannerreadfile {

    public static void main(String[] args) {

        try (Scanner sc = new Scanner(new File("sample.txt"))) {
            while (sc.hasNext()) {
                System.out.println(sc.nextLine());
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

    }
}

sample.txt

The Scanner class is used to get user input, and it is found in the java.util package. To use the Scanner class, create an object of the class.


Output:
C:\javademo>java JavaScannerreadfile
The Scanner class is used to get user input, and it is found in the java.util package. To use the Scanner class, create an object of the class
C:\javademo>
 

3.    Reading Data from -  String

import java.util.Scanner;

public class JavaScannerstr {

public static void main(String[] args) {
   
String str = "Scanner Example";

Scanner sc = new Scanner(str);

System.out.println("String is " + sc.nextLine());

sc.close();

}
}

Output:
C:\javademo>javac JavaScannerstr.java
C:\javademo>java JavaScannerstr
String is Scanner Example
C:\javademo>
 

 

 

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Reading Delimiter String in Java

import java.util.Scanner;


public class JavaScannerdelimeter {

    public static void main(String[] args) { 

    String input = "A,B,C,D,E";

     try (Scanner s = new Scanner(input).useDelimiter(",")) {

         while (s.hasNext()) {
                System.out.println(s.next());
            }
        }

    }
}

Methods  list available in Scanner class to read data:

nextBoolean()                   Reads a boolean value from the keyboard.
nextByte()                         Reads a byte value from the  keyboard.

nextDouble()                     Reads a double value from the keyboard.
nextFloat()                        Reads a float value from the keyboard.
nextInt()                            Reads a int value from the keyboard.
nextLine()                         Reads a String value from the keyboard. 

nextLong()                        Reads a long value from the keyboard.
nextShort()                        Reads a short value from the keyboard.


 

 

Following diagram shows - How Scanner works

 

 

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