Scanner Class

Intermediate ~15 min read

The Scanner class is a simple text scanner which can parse primitive types and strings using regular expressions. It is commonly used for reading input from the console or parsing files.

Reading from Console

Scanner scanner = new Scanner(System.in);
System.out.print("Enter your name: ");
String name = scanner.nextLine();
System.out.println("Hello " + name);

Reading from File

File file = new File("data.txt");
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
    String data = scanner.nextLine();
    System.out.println(data);
}
scanner.close();

Full Example

import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;

public class IoScanner {
    public static void main(String[] args) {
        // Reading from a file using Scanner
        try {
            Scanner scanner = new Scanner(new File("sample.txt"));
            System.out.println("Reading file with Scanner:");
            while (scanner.hasNextLine()) {
                String line = scanner.nextLine();
                System.out.println(line);
            }
            scanner.close();
        } catch (FileNotFoundException e) {
            System.out.println("File not found: " + e.getMessage());
        }
        
        // Reading different data types
        try {
            Scanner scanner = new Scanner(new File("data.txt"));
            System.out.println("\nReading different types:");
            while (scanner.hasNext()) {
                if (scanner.hasNextInt()) {
                    int number = scanner.nextInt();
                    System.out.println("Integer: " + number);
                } else if (scanner.hasNextDouble()) {
                    double decimal = scanner.nextDouble();
                    System.out.println("Double: " + decimal);
                } else {
                    String text = scanner.next();
                    System.out.println("String: " + text);
                }
            }
            scanner.close();
        } catch (FileNotFoundException e) {
            System.out.println("File not found: " + e.getMessage());
        }
    }
}

Output

Click Run to execute your code

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Reading from Console

Reading from File

Full Example

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