Introduction#

Until now, we have stored values directly inside our Java programs.

For example:

int age = 20;
String name = "Ravi";

But in real applications, we often need to get values from the user while the program is running.

For example:

Enter your name: Ravi
Enter your age: 20

Java provides the Scanner class to take input from the user.

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What Is Scanner?#

Scanner is a Java class used to read input from the user.

It belongs to the java.util package.

To use Scanner, we first import it:

import java.util.Scanner;

Then we create a Scanner object:

Scanner sc = new Scanner(System.in);

Here:

• Scanner is the class.
• sc is the reference variable.
• new Scanner(System.in) creates the Scanner object.
• System.in represents input from the keyboard.

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Basic Scanner Program#

import java.util.Scanner;

class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        System.out.print("Enter your age: ");
        int age = sc.nextInt();

        System.out.println("Your age is: " + age);
    }
}

Output

Enter your age: 20
Your age is: 20

The statement:

int age = sc.nextInt();

reads an integer entered by the user and stores it in age.

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Scanner Methods#

Different data types use different Scanner methods.

Data Type	Scanner Method
byte	nextByte()
short	nextShort()
int	nextInt()
long	nextLong()
float	nextFloat()
double	nextDouble()
boolean	nextBoolean()
String	next()
String with spaces	nextLine()

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Taking String Input#

Scanner provides two commonly used methods for reading strings:

next()

and

nextLine()

Using next()#

next() reads only one word.

String name = sc.next();

If the user enters:

Ravi Kumar

only:

Ravi

will be read.

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Using nextLine()#

nextLine() reads the complete line.

String name = sc.nextLine();

If the user enters:

Ravi Kumar

the complete value:

Ravi Kumar

will be read.

Simple Difference#

next()      → reads one word
nextLine()  → reads the complete line

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Taking Character Input

Scanner does not have a nextChar() method.

To read a character, we can use:

char grade = sc.next().charAt(0);

Example:

import java.util.Scanner;

class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        System.out.print("Enter grade: ");
        char grade = sc.next().charAt(0);

        System.out.println("Grade = " + grade);
    }
}

If the user enters:

A

the value stored in grade is:

A

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Taking Multiple Inputs

We can use the same Scanner object to take multiple inputs.

import java.util.Scanner;

class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        System.out.print("Enter name: ");
        String name = sc.nextLine();

        System.out.print("Enter age: ");
        int age = sc.nextInt();

        System.out.print("Enter percentage: ");
        double percentage = sc.nextDouble();

        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
        System.out.println("Percentage: " + percentage);
    }
}

Example:

Enter name: Ravi Kumar
Enter age: 20
Enter percentage: 85.5

Name: Ravi Kumar
Age: 20
Percentage: 85.5

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Check Your Understanding

1. What will be the output?#

Scanner sc = new Scanner(System.in);

int a = sc.nextInt();
int b = sc.nextInt();

System.out.println(a + b);

If the user enters:

10
20

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2. What is the difference between these two?#

String name = sc.next();

and

String name = sc.nextLine();

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3. Which Scanner method would you use for each?#

• Student age
• Product price
• Student name with spaces
• Student grade
• Passed or failed

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4. Find the problem#

int age = sc.nextInt();
String name = sc.nextLine();

Why can this cause a problem when reading the name, and how can you fix it?