Scanner vs. BufferedReader

java

exception-handling

performance-optimization

multithreading

byAlex Kataev·Oct 20, 2024

Choose Scanner when simplicity and parsing primitives are essential. It provides helpful methods like nextInt() and nextDouble() for quick data crunching:

// "Anyone called for a Scanner? I've got nextInt() loaded."
Scanner scanner = new Scanner(System.in);
// "Hey look, it's a number! And not just any number...it's an Int!"
int num = scanner.nextInt();

Turn to BufferedReader for unparalleled speed when dealing with large text tasks, using its super-efficient readLine():

// "BufferedReader reporting for duty!"
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
// "Listen up, I've got a line to read here."
String str = reader.readLine();

To put it simply, Scanner is your friendly neighborhood Spiderman, while BufferedReader is the Flash when it comes to performance.

Task-based selection criterion

Which situations suit Scanner?

Interactive apps: with modest user input and processing time.
Delimited files: use Scanner to parse tokens in a CSV-like environment.
Writing clean and simple code: the priority is readability and brevity over performance.

Where does BufferedReader shine?

Bulk file reading: When processing speed for large files is vital.
Log processing: BufferedReader is tailor-made for efficient line-wise reads.
Threaded operations: Its intrinsic synchronization supports multi-thread operations.

Exception handling and API considerations

While Scanner conveniently swallows IOExceptions, it might not be the best practice, especially if you prefer robust error handling. On the other hand, BufferedReader does not sugarcoat and nudges you toward effective exception management.

When it comes to APIs, while Scanner rolls out the red carpet with a plethora of nextXxx() methods for different types, BufferedReader opts for basic reads. It wraps around other readers, improving efficiency.

Performance-centric considerations

Buffer sizes - why do they matter?

Scanner: With its relatively modest buffer size (1024 chars), Scanner may struggle with data-intensive tasks.
BufferedReader: Its substantial buffer size (8192 chars) makes it the Usain Bolt for large file processing.

Parsing vs just reading - what to choose when?

Scanner's parsing: Provides convenience but adds an overhead.
BufferedReader's reading: Keeping it simple, it avoids extra steps, thus enhancing speed.

Tailoring your tool choice

Customizability:

Scanner: Lets you choose your delimiters to match all sorts of input patterns.
BufferedReader: Adheres to straightforward line breaks as delimiters but excels in consistent streaming.

Multithreading:

Scanner: without inherent synchronization, it's not your comrade for concurrent operations.
BufferedReader: Complies with synchronous access needs for multitasking programs.