What Are the Most Efficient Methods to Read Input from System.in in Java?

What are the most efficient ways to read multiple integers from System.in in Java?

Scanner scanner = new Scanner(System.in); while (scanner.hasNextInt()) { int num = scanner.nextInt(); // process num }

While the `Scanner` class provides a simple API for reading input, it may not be the fastest option available in Java, especially when reading large volumes of data. For improved performance, techniques such as using `BufferedReader` with `InputStreamReader` or `DataInputStream` can significantly enhance the reading speed from standard input.

BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String line; while ((line = reader.readLine()) != null) { String[] numbers = line.split(" "); for (String number : numbers) { int num = Integer.parseInt(number); // process num } }

Causes

• Using `Scanner` can lead to slower performance due to its regex parsing and internal buffer management.
• Frequent method calls in `Scanner` may incur overhead compared to reading in bulk.

Solutions

• Utilize `BufferedReader` for reading input in larger chunks, which reduces overhead from multiple function calls.
• Implement `String.split()` to parse input strings, allowing for manipulation of the entire input at once.
• Consider `DataInputStream` for binary data, or use `Files.newBufferedReader(Paths.get("filename"))` for file-based input.

Mistake: Not handling `IOException` when using `BufferedReader` or other stream classes.

Solution: Use a try-catch block to handle exceptions properly.

Mistake: Forgetting to close the BufferedReader, leading to resource leaks.

Solution: Always close the BufferedReader in a finally block or use try-with-resources.