Java User Input - Scanner Class

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The most common way to take user input in Java is using the Scanner class. It is a part of java.util package. The scanner class can handle input from different places, like as we are typing at the console, reading from a file, or working with data streams. This class was introduced in Java 5. Before that, we used the BufferedReader class (introduced in Java 1.1). As a beginner, we will suggest to use Scanner class.

Using Scanner in Our Code

Follow these steps to take user input using Scanner class:

• Import the Scanner class using import java.util.Scanner;
• Create the Scanner object and connect Scanner with System.in by passing it as an argument i.e., Scanner sc = new Scanner(System.in);
• When we want to ask the user for input, first print a prompt message so they know what to enter. Then use one of Scanner's handy methods to read the response:
  • nextInt() for whole numbers
  • nextLine() for full text lines
  • nextDouble() for decimal numbers
  • next() for single words

Example: Let us go through a simple example where we get two numbers from the user and add them together:

// Taking user input
import java.util.Scanner;

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

        // Creating Scanner class object
        Scanner scn = new Scanner(System.in);

        // Enter first input
        System.out.print("Enter First Number: ");
        int a = scn.nextInt();

        System.out.print("Enter Second Number: ");
        int b = scn.nextInt();

        System.out.println("Sum: " + (a + b));

        // Closing the scanner to release resources
        scn.close();
    }
}

Output:

Methods of Scanner Class

We have discussed few methods of Scanner class above, but the Scanner class provides some more methods to read different data types, let us discuss those in the below table:

Example: Here, we are taking multiple user inputs like string, float, double etc. and using the above mentioned methods of Scanner Class.

// Taking multiple user input using Scanner Class
import java.util.Scanner;

public class Geeks
{
    public static void main(String[] args)
    {
        // Scanner definition
        Scanner scn = new Scanner(System.in);

        // input is a string(one word)
        System.out.print("Enter a word: ");
        String str1 = scn.nextLine();
        System.out.println("Entered String str1: " + str1);

        // input is a string(complete sentence)
        System.out.print("Enter a sentence: ");
        String str2 = scn.nextLine();
        System.out.println("Entered String str2: " + str2);

        // input is an integer
        System.out.print("Enter an integer: ");
        int x = Integer.parseInt(scn.nextLine());
        System.out.println("Entered Integer: " + x);

        // input is a float value
        System.out.print("Enter a float value: ");
        float f = Float.parseFloat(scn.nextLine());
        System.out.println("Entered FloatValue: " + f);

        scn.close();
    }
}

Output:

Another method to take user input is using BufferedReader Class. It is a simple class that is used to read a sequence of characters. It provides several methods, including:

• read(): Reads a single character.
• read(char[] cbuf): Reads an array of characters.
• readLine(): Reads an entire line of text.

To know more about BufferedReader Class, please refer to the article - BufferedReader Class in Java

BufferedReader vs Scanner Class