I am working on a competitive programming challenge where performance is key. I need to know the best way to take multiple integer inputs from a single line using BufferedReader instead of Scanner. Specifically, how do I parse the space-separated string into individual int variables or an array without hitting memory overhead or slowing down the execution time significantly?
3 answers
To achieve high performance, you should combine BufferedReader with StringTokenizer. First, read the entire line using readLine(). Then, pass that string into a StringTokenizer instance. You can then use a loop with nextToken() and Integer.parseInt() to extract each integer. This method is significantly faster than using Scanner.nextInt() because it avoids the overhead of regular expression parsing. It’s the standard approach for competitive coding and high-load backend systems where every millisecond counts toward the final execution time.
While StringTokenizer is the traditional route, wouldn't using the String.split() method be more readable for most developers? Is there a specific performance threshold where the split method's array creation becomes a bottleneck compared to the legacy tokenizer approach for modern Java versions?
You can also use Java 8 Streams by splitting the line and mapping it: Arrays.stream(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();. It is very concise but slightly slower than the manual loop.
I definitely agree with Robert here. The Stream API makes the code much more maintainable for team projects, even if it trades off a tiny bit of raw speed for that elegant one-liner syntax.
Michael, you hit on a great point. While split(" ") is cleaner, it creates a new String array and uses regex internally, which consumes more heap memory. For small inputs, it's fine, but in data-heavy Software Development tasks, StringTokenizer is preferred because it processes the string as a stream of tokens without the extra overhead of creating an intermediate array.