如何准确计算Java程序写入或读取文件所需的时间？

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class FileIOBenchmark {

    public static void main(String[] args) {
        String inputFile = "input.txt";
        String outputFile = "output.txt";

        long startTime = System.nanoTime();
        readFile(inputFile);
        long endTime = System.nanoTime();
        long readTime = endTime - startTime;
        System.out.println("读取文件所需时间（纳秒）：" + readTime);

        startTime = System.nanoTime();
        writeFile(outputFile);
        endTime = System.nanoTime();
        long writeTime = endTime - startTime;
        System.out.println("写入文件所需时间（纳秒）：" + writeTime);
    }

    private static void readFile(String file) {
        try (BufferedReader br = new BufferedReader(new FileReader(file))) {
            String line;
            while ((line = br.readLine()) != null) {
                // 处理文件内容
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static void writeFile(String file) {
        try (BufferedWriter bw = new BufferedWriter(new FileWriter(file))) {
            for (int i = 0; i < 1000; i++) {
                bw.write("这是一行文本\n");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}