I am currently learning Java and I have been told that using BufferedReader is significantly faster than using the Scanner class for large inputs. However, I am struggling with the syntax because it seems to require wrapping multiple classes like InputStreamReader. Could someone provide a clear example of how to read both strings and integers from the console using this method? Also, why is it necessary to handle IOExceptions every time I use it, and what is the most modern way to ensure the stream is closed properly?
3 answers
Using BufferedReader is indeed the preferred way for high-volume input because it buffers characters for efficient reading. To use it, you must wrap an InputStreamReader around System.in. For example: BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));. To read a string, you use reader.readLine(), and for integers, you must wrap that call in Integer.parseInt().
Regarding your question about exceptions, readLine() is a "checked" operation because the underlying stream could fail (e.g., if the input is disconnected), so Java forces you to use a try-catch block or throw the exception. For the modern approach, I highly recommend the "try-with-resources" statement, which automatically closes the reader for you once the block is finished, preventing memory leaks in your application.
When you are parsing integers using Integer.parseInt(reader.readLine()), how are you handling potential NumberFormatException errors if the user accidentally enters a letter or a blank space instead of a digit? This is one of the main areas where Scanner is actually a bit easier since it has hasNextInt(), whereas with BufferedReader, you have to manually validate the string content before converting it.
BufferedReader is much faster than Scanner because it has a much larger buffer—8KB by default. Just remember to import java.io.* and use readLine() for all inputs.
Donna is right about the speed! I recently benchmarked them for a competitive programming task, and BufferedReader was nearly 3 times faster when processing over a million lines of text. As Karen mentioned, just make sure to handle that IOException or your code won't even compile in a standard Java IDE.
Steven, that is a valid concern for beginners. In my experience, I usually write a small helper utility method that wraps the parsing in a loop until the user provides valid numeric data. While it adds a few lines of code compared to Scanner, the performance gains in data-heavy domains like Data Science or backend processing make the extra effort completely worth it. Do you have a preferred validation pattern for this?