Scanner class

In Java, the Scanner class is used to read input from the user. This input can be anything typed on the keyboard, such as strings, integers, or decimals.

Step 1: Import the Scanner Class

To use the Scanner class, you first need to import it from the java.util package:

import java.util.Scanner;

This line of code allows you to use the Scanner class in your programme.

Creating a Scanner Object

Once you’ve imported the Scanner class, you need to create a Scanner object (which we will refer to as sc in this example):

Scanner sc = new Scanner(System.in);

• Scanner is the class name.
• sc is the variable name (you can choose any name for this variable).
• System.in refers to the standard input stream (the keyboard).

Common Scanner Methods

The Scanner class has many methods to read different types of input. Below are the most commonly used methods:

Example: Reading User Input

Here’s a simple Java programme that demonstrates how to read a user’s name and age using the Scanner class:

import java.util.Scanner;

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

        // Create a Scanner object to read input from the user
        Scanner sc = new Scanner(System.in);

        // Ask for the user's full name
        System.out.print("Enter your full name: ");
        String name = sc.nextLine();  // Reads the full name

        // Ask for the user's age
        System.out.print("Enter your age: ");
        int age = sc.nextInt();  // Reads the age (integer)

        // Display the collected information
        System.out.println("Your full name is: " + name);
        System.out.println("Your age is: " + age);

        // Close the Scanner object to free up resources
        sc.close();
    }
}

• sc.nextLine(): Reads the whole line of input (name, in this case).
• sc.nextInt(): Reads an integer input (age, in this case). It doesn’t handle decimals or anything other than whole numbers.
• sc.close(): After you’re done using the Scanner, always call sc.close() to free up system resources.

Summary

• Scanner class in Java is used to read input from the user.
• Import it with import java.util.Scanner; before use.
• Common methods: next() (word), nextLine() (sentence), nextInt() (integer), nextDouble() (decimal), nextBoolean() (boolean).
• Always close the Scanner object with sc.close() when done.

Further Reading

• Java Scanner class
• Java primitive data types
• Java String