What to Import for Scanner Java: A Practical Guide

Learn what to import for Scanner Java, including java.util.Scanner and optional file-input imports, with practical examples, best practices, and common pitfalls.

Scanner Check Team

February 14, 2026·5 min read

Scanner OCR Document Scanning Scanner Setup

Java Scanner Intro - Scanner Check (illustration)

Quick AnswerDefinition

To use the Scanner class in Java, import java.util.Scanner. For file-based input, also import java.io.File and java.io.FileNotFoundException. The minimal setup reads from System.in, while more complex scenarios may require File or other I/O classes. This quick guide shows the essential import and how it shapes your code, based on real-world use cases.

What to import for scanner java

In Java, the central question for beginners is often: what to import for scanner java? The essential import is java.util.Scanner, which provides methods to parse primitive types and strings from various input sources. If you plan to read input from files or other streams, you should also import the corresponding I/O classes, such as java.io.File and java.io.FileNotFoundException. According to Scanner Check, starting with the minimal required imports helps keep your code clean and maintainable, especially in tutorials and onboarding materials. This section introduces the minimal import set and then expands to common variations you will encounter in real projects.

Java

// Minimal import for console input
import java.util.Scanner;

public class ConsoleInput {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    System.out.print("Enter a value: ");
    String s = sc.nextLine();
    System.out.println("You entered: " + s);
    sc.close();
  }
}

Why this import matters: The import determines which Scanner constructor you can use (System.in, a File, or a string source). Keeping imports minimal reduces compiler churn and clarifies dependencies for readers.

Java

// Optional: reading from a file requires additional imports
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;

This helps explain how the import set expands when you shift from console to file-based input.

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Steps

Estimated time: 15-30 minutes

1
Set up project and imports
Create a small Java project and add the minimal imports for Scanner. Start with the ConsoleInput example to confirm standard input works before introducing File input.
Tip: Keep the import scope small; only add File-related imports when you switch to file input.
2
Write a console input sample
Implement a class that reads a line from System.in and prints it back. Compile and run to verify the Scanner is functioning as expected.
Tip: Use try-with-resources or close() to release the Scanner when finished.
3
Add file input
Extend the program to read from a file using new File and Scanner(File). Handle FileNotFoundException gracefully.
Tip: Always close the scanner or use try-with-resources to avoid resource leaks.
4
Experiment with delimiters
Configure the scanner with a custom delimiter to tokenize input strings, demonstrating how delimiters affect next() and nextLine().
Tip: Remember to consume remaining newline when mixing nextInt/nextLine.
5
Run and verify edge cases
Test empty input, whitespace, and malformed data to ensure your import and parsing logic are robust.
Tip: Add basic error handling to catch InputMismatchException or similar issues.

Pro Tip: Always import the exact class you need; avoid wildcard imports to keep dependencies explicit.

Warning: Do not forget to close the Scanner to prevent resource leaks; prefer try-with-resources when possible.

Note: When reading numbers, consider locale settings to avoid parsing errors in different regions.

Prerequisites

Required

Java JDK 8 or higher↗
Required
A Java IDE or editor (e.g., VS Code, IntelliJ)↗
Required
Basic command line knowledge
Required

Optional

Build tool (Maven or Gradle) - optional but common↗
Optional
Familiarity with exceptions and try-with-resources
Optional

Commands

Action	Command
Compile Java fileFrom project root; ensure JDK is in PATH	—
Run compiled classExecute from the directory containing the class file	—
Compile with dependencies in a packageUse -cp for additional libraries if needed	—
List Java versionVerify JDK 8+ in use	—

Common Questions

Do I always need to import java.util.Scanner to use Scanner in Java?

Yes, to instantiate Scanner for input sources in Java you typically import java.util.Scanner. If you read from files, you’ll also need java.io.File and related exceptions. This keeps your code focused and minimizes unnecessary imports.

What is the difference between System.in and File input for Scanner?

System.in streams keyboard input, while File input reads from a file. Each source uses a different Scanner constructor, which means different import needs and exception handling. Start with System.in for learning, then add File input when you need file-based data.

How do I avoid the common pitfall of nextLine after nextInt?

Call a consuming newline after nextInt (or use a single-line parsing strategy). This prevents the leftover newline from being treated as input for the subsequent nextLine call.

Can Scanner handle locales or only basic whitespace?

Scanner supports locales for number formats and word boundaries. Set the locale explicitly if your data uses a locale-specific format to avoid parsing errors.

Is Scanner thread-safe for concurrent reads?

Scanner is not inherently thread-safe. To share input safely across threads, synchronize access or use separate scanners per thread with distinct input sources.

When should I prefer BufferedReader over Scanner?

For high-performance tokenization of large inputs, BufferedReader with manual parsing is often faster than Scanner. Use Scanner when you value simplicity and readability over micro-optimizations.