我可以更快地制作以下代码吗

Question

I would like to make the following code faster, without changing the reading/writing from standard console. The first line contains the number of inputs and the subsequent lines contain a set of Integer s.

import java.util.StringTokenizer;

public class Main {
    public static void main(String[] args) throws java.lang.Exception {
        try {
            java.io.BufferedReader r = new java.io.BufferedReader(new java.io.InputStreamReader(System.in));
            int a = Integer.parseInt(r.readLine());
            for (int i = 0; i < a; i++) {
                StringTokenizer st = new StringTokenizer(r.readLine());
                while (st.hasMoreTokens()) {
                    int first = Integer.parseInt(st.nextToken());
                    int second = Integer.parseInt(st.nextToken());
                    if (first < second)
                        System.out.println("<");
                    else if (first > second)
                        System.out.println(">");
                    else
                        System.out.println("=");
                }
            }
        } catch (Exception e) {
            System.err.print(e.getMessage());
        }

    }
}

Answer 1

You are performing a lot of redundant autoboxing and outboxing there which could be saved if you define first and second as primitive int s instead of java.lang.Integer wrapper classes. I doubt, however, that for any reasonable size of input you'd even notice the difference.

Answer 2

Here are a few suggestions, I am not sure these will help a lot.

1) This,

                if (first < second)
                    System.out.println("<");
                else if (first > second)
                    System.out.println(">");
                else
                    System.out.println("=");

can be changed to

                    System.out.println(first < second
                                       ? "<"
                                       : first > second
                                         ? ">"
                                         : "="
                                      );

2) Since you are using a throws clause and your try-catch does nothing you can remove it.

3) Here,

                int first = Integer.parseInt(st.nextToken());
                int second = Integer.parseInt(st.nextToken());

You are not checking for hasMoreTokens() the second time.

4) Use split() instead of StringTokenizer . More on that here and here .

Answer 3

You may consider to use the BufferedReader 's constructor below:

public BufferedReader(Reader in, int sz)

Giving the sz parameter a reasonable high value , can avoid the buffer to be refilled too often.

---

As a side note, while readLine() retuns null if the end of the stream has been reached, it's better to check its return value before calling new StringTokenizer(r.readLine()) and Integer.parseInt(r.readLine()) .
The edited class follows:

public class Main {

    public static void main(String[] args) {
        BufferedReader r;
        String line;
        StringTokenizer st;
        int a, first, second;

        r = new BufferedReader(new InputStreamReader(System.in), 4096);
        try {
            line = r.readLine();
            if (line != null) {
                a = Integer.parseInt(line);
                for (int i = 0; i < a; ++i) {
                    line = r.readLine();
                    if (line == null)
                        break;
                    st = new StringTokenizer(line);
                    while (st.hasMoreTokens()) {
                        first = Integer.parseInt(st.nextToken());
                        second = Integer.parseInt(st.nextToken());
                        if (first < second)
                            System.out.println("<");
                        else if (first > second)
                            System.out.println(">");
                        else
                            System.out.println("=");
                    }
                }
            }
            r.close();
        } catch (Exception e) {
            System.err.print(e.getMessage());
        }
    }
}