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Java FileFilter 與 BufferedReader 讀行處理實戰代碼

編輯：Java 相關知識

實戰場景：批量讀取目錄下所有 .txt 壓測日誌，提取關鍵指標（吞吐量、QPS、延遲、錯誤率等）並彙總。展示 FileFilter 過濾與 BufferedReader 高效讀行的最佳實踐。

完整實戰代碼

package com.cjonline.foundation.evisa;

import java.io.*;
import java.math.BigDecimal;

public class Test {
    public static void main(String[] args) throws Exception {
        // 1. FileFilter 過濾 .txt 檔案
        File[] files = new File("src").listFiles(new FileFilter() {
            @Override
            public boolean accept(File file) {
                return file.getName().endsWith(".txt");
            }
        });

        // 2. 定義待提取指標關鍵字
        String[] keys = {
            "Total transferred:", "Requests per second:", "[ms] (mean)",
            "Time per request:", "Transfer rate:", "Failed requests:", "Write errors:"
        };

        // 3. 逐檔處理
        for (File file : files) {
            System.out.println("---------【 file name : " + file.getName() + "】----------");
            try (FileInputStream is = new FileInputStream(file);
                 BufferedReader br = new BufferedReader(new InputStreamReader(is))) {
                
                BigDecimal[] results = calPress(br);
                for (int i = 0; i < keys.length; i++) {
                    System.out.println(keys[i] + "    " + results[i]);
                }
                System.out.println();
            }
        }
    }

    // 4. 解析邏輯：按行讀取 + 前綴/後綴匹配 + 分割提取數值
    private static BigDecimal[] calPress(BufferedReader br) throws IOException {
        BigDecimal[] res = new BigDecimal[7];
        Arrays.fill(res, BigDecimal.ZERO);
        
        String line;
        while ((line = br.readLine()) != null) {
            if (line.startsWith("Total transferred:")) {
                res[0] = res[0].add(extractValue(line, -2));
            } else if (line.startsWith("Requests per second:")) {
                res[1] = res[1].add(extractValue(line, -3));
            } else if (line.endsWith("[ms] (mean)")) {
                res[2] = res[2].add(extractValue(line, -3));
            } else if (line.startsWith("Time per request:") && !line.endsWith("[ms] (mean)")) {
                res[3] = res[3].add(extractValue(line, -7));
            } else if (line.startsWith("Transfer rate:")) {
                res[4] = res[4].add(extractValue(line, -3));
            } else if (line.startsWith("Failed requests:")) {
                res[5] = res[5].add(extractValue(line, -1));
            } else if (line.startsWith("Write errors:")) {
                res[6] = res[6].add(extractValue(line, -1));
            }
        }
        return res;
    }

    // 輔助：分割行並提取指定索引位置的數值
    private static BigDecimal extractValue(String line, int indexFromEnd) {
        String[] parts = line.split("\\s+");
        String valStr = parts[parts.length + indexFromEnd]; // 負索引從後往前
        return BigDecimal.valueOf(Double.parseDouble(valStr));
    }
}