Scanner class worksheets for High School AP Computer Science A (Java)

📚 Topic Summary

The Scanner class in Java is your go-to tool for reading input from various sources, like the keyboard or files. It breaks the input into tokens using delimiters (usually whitespace). Think of it like a super-smart assistant that helps your program understand what the user is typing or what's written in a file. With the Scanner class, you can easily grab integers, doubles, strings, and more, making your programs interactive and data-driven!

Scanner objects are initialized by passing an InputStream object (like System.in for keyboard input). They use methods like nextInt(), nextDouble(), and nextLine() to parse input. Understanding the Scanner class is crucial for any AP Computer Science student because it's used in so many programs that require user interaction or file processing. Let's test your knowledge!

🧠 Part A: Vocabulary

Match the following terms with their definitions:

Answers:

• 🔍 1 - A
• 💡 2 - B
• 📝 3 - C
• 🧮 4 - D
• 💻 5 - E

✍️ Part B: Fill in the Blanks

The Scanner class is used to read ______ from various sources. A ______ is a sequence of characters separated by a ______. To read an integer, you use the ______ method, and to read a line of text, you use the ______ method.

Answers:

• 🔍 input
• 💡 token
• 📝 delimiter
• 🧮 nextInt()
• 💻 nextLine()

🤔 Part C: Critical Thinking

Explain a scenario where using the Scanner class would be essential in a real-world application you might encounter in your daily life. Provide a code example to demonstrate the implementation.

Answer:

• 🔍 One real-world application is reading data from a configuration file for a software application. For example, a game might read the player's preferences (volume level, screen resolution) from a file using the Scanner class.

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

public class ConfigReader {
    public static void main(String[] args) {
        try {
            File configFile = new File("config.txt");
            Scanner scanner = new Scanner(configFile);

            while (scanner.hasNextLine()) {
                String line = scanner.nextLine();
                String[] parts = line.split("=");
                if (parts.length == 2) {
                    String key = parts[0].trim();
                    String value = parts[1].trim();
                    System.out.println("Key: " + key + ", Value: " + value);
                }
            }
            scanner.close();
        } catch (FileNotFoundException e) {
            System.out.println("Config file not found.");
        }
    }
}