Java中使用的内存为0 KB

在一次竞争性编程竞赛中，我浏览了一些用Java编写的代码，但我根本无法理解他们的代码所使用的内存是0kb

 import java.io.*;
import java.util.*;

public class C {
    FastScanner in = new FastScanner(System.in);
    PrintWriter out = new PrintWriter(System.out);

    public void run() {
        int n = in.nextInt(), m = in.nextInt(), k = in.nextInt();
        int[] a = in.nextIntArray(n);

        long[] sum = new long[n+1];
        for (int i = 1; i <= n; i++) {
            sum[i] = sum[i-1] + a[i-1];
        }

        long[] cur = new long[n+1];
        long[] old = new long[n+1];

        for (int i = 1; i <= k; i++) {
            Arrays.fill(cur, Long.MIN_VALUE / 2);
            for (int j = i * m; j <= n; j++) {
                cur[j] = Math.max(cur[j-1], old[j-m] + sum[j] - sum[j-m]);
            }
            long[] temp = cur;
            cur = old;
            old = temp;
        }
        System.out.println(old[n]);
        out.close();
    }

    public static void main(String[] args) {
        new C().run();
    }

    public void mapDebug(int[][] a) {
        System.out.println("--------map display---------");

        for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a[i].length; j++) {
                System.out.printf("%3d ", a[i][j]);
            }
            System.out.println();
        }

        System.out.println("----------------------------");
        System.out.println();
    }

    public void debug(Object... obj) {
        System.out.println(Arrays.deepToString(obj));
    }

    class FastScanner {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;

        public FastScanner(InputStream stream) {
            this.stream = stream;
            //stream = new FileInputStream(new File("dec.in"));

        }

        int read() {
            if (numChars == -1)
                throw new InputMismatchException();
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }

        boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        boolean isEndline(int c) {
            return c == '\n' || c == '\r' || c == -1;
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        int[] nextIntArray(int n) {
            int[] array = new int[n];
            for (int i = 0; i < n; i++)
                array[i] = nextInt();

            return array;
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        long[] nextLongArray(int n) {
            long[] array = new long[n];
            for (int i = 0; i < n; i++)
                array[i] = nextLong();

            return array;
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        double[] nextDoubleArray(int n) {
            double[] array = new double[n];
            for (int i = 0; i < n; i++)
                array[i] = nextDouble();

            return array;
        }

        String next() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        String[] nextStringArray(int n) {
            String[] array = new String[n];
            for (int i = 0; i < n; i++)
                array[i] = next();

            return array;
        }

        String nextLine() {
            int c = read();
            while (isEndline(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndline(c));
            return res.toString();
        }
    }
}

import java.io.*；
导入java.util.*；
公共C类{
FastScanner in=新的FastScanner（System.in）；
PrintWriter out=新的PrintWriter（System.out）；
公开募捐{
int n=in.nextInt（），m=in.nextInt（），k=in.nextInt（）；
int[]a=in.nextinArray（n）；
长[]和=新长[n+1]；
对于（int i=1；i
当涉及到执行时间和内存时，Java中可以使用的基本优化是什么。
这个问题有点太宽泛了，整本书都是关于这个主题的。你在
public void debug（Object…obj）
中看到的被称为“varargs”（如果你想用正手的话，可以使用变量arity参数）。你可以阅读有关它的文章。例如，它现在经常被使用，所以最好意识到它的存在，特别是它潜在的问题。