diff --git a/src/main/java/com/pcdd/sonovel/action/Action.java b/src/main/java/com/pcdd/sonovel/action/Action.java
deleted file mode 100644
index 8a55a58..0000000
--- a/src/main/java/com/pcdd/sonovel/action/Action.java
+++ /dev/null
@@ -1,12 +0,0 @@
-package com.pcdd.sonovel.action;
-
-import org.jline.terminal.Terminal;
-
-/**
- * @author pcdd
- */
-public interface Action {
-
-    void execute(Terminal terminal);
-
-}
diff --git a/src/main/java/com/pcdd/sonovel/action/CheckUpdateAction.java b/src/main/java/com/pcdd/sonovel/action/CheckUpdateAction.java
index 47863ef..b6173ed 100644
--- a/src/main/java/com/pcdd/sonovel/action/CheckUpdateAction.java
+++ b/src/main/java/com/pcdd/sonovel/action/CheckUpdateAction.java
@@ -91,13 +91,14 @@ private String getDownloadUrl(String version) {
 
     private void download(String url) {
         // HEAD 请求不会下载文件内容，只会返回文件的元数据（例如文件大小）
-        long fileSize = HttpUtil.createRequest(Method.HEAD, url)
+        HttpResponse resp = HttpUtil.createRequest(Method.HEAD, url)
                 .timeout(10_000)
-                .execute()
-                .contentLength();
+                .execute();
+        long fileSize = resp.contentLength();
+        resp.close();
+
         // 设置进度条
         ProgressBar pb = new ProgressBar("下载最新版", fileSize);
-
         //  下载到上一级路径
         File file = new File(System.getProperty("user.dir")).getParentFile();
 
@@ -117,10 +118,11 @@ public void progress(long total, long step) {
             @Override
             public void finish() {
                 pb.setExtraMessage("下载完成");
-                pb.close();
                 Console.log("<== 下载位置: {}", file + File.separator + FileUtil.getName(url));
             }
         });
+
+        pb.close();
     }
 
-}
+}
\ No newline at end of file
diff --git a/src/main/java/com/pcdd/sonovel/core/ChapterFilter.java b/src/main/java/com/pcdd/sonovel/core/ChapterFilter.java
index 0120fa6..5b7689c 100644
--- a/src/main/java/com/pcdd/sonovel/core/ChapterFilter.java
+++ b/src/main/java/com/pcdd/sonovel/core/ChapterFilter.java
@@ -29,7 +29,7 @@ public String filter(Chapter chapter) {
      * 建造者类，用于动态组合过滤步骤
      */
     public class FilterBuilder {
-        private String title;
+        private final String title;
         private String content;
         private boolean applyEscapeFilter;
         private boolean applyAdsFilter;
diff --git a/src/main/java/com/pcdd/sonovel/handle/EpubMergeHandler.java b/src/main/java/com/pcdd/sonovel/handle/EpubMergeHandler.java
index 0965f90..5f9cbf3 100644
--- a/src/main/java/com/pcdd/sonovel/handle/EpubMergeHandler.java
+++ b/src/main/java/com/pcdd/sonovel/handle/EpubMergeHandler.java
@@ -24,6 +24,8 @@
  */
 public class EpubMergeHandler implements PostProcessingHandler {
 
+    public static final String COVER_NAME = "cover.html";
+
     @SneakyThrows
     @Override
     public void handle(Book b, File saveDir) {
@@ -52,8 +54,7 @@ public void handle(Book b, File saveDir) {
         meta.setRights(List.of("本电子书由 so-novel(https://github.com/freeok/so-novel) 制作生成。仅供交流使用，不得用于商业用途。"));
 
         // 添加封面页
-        book.addSection("封面", new Resource(ResourceUtil.readBytes("templates/chapter_cover.html"),
-                "cover.html"));
+        book.addSection("封面", new Resource(ResourceUtil.readBytes("templates/chapter_cover.html"), COVER_NAME));
 
         List<File> files = FileUtils.sortFilesByName(saveDir);
         int len = String.valueOf(files.size()).length();
@@ -77,7 +78,7 @@ public void handle(Book b, File saveDir) {
 
         // 设置 guide，用于指定封面
         book.getGuide().addReference(new GuideReference(new Resource(ResourceUtil.readBytes("templates/chapter_cover.html"),
-                "cover.html"), "封面", "cover.html"));
+                COVER_NAME), "封面", COVER_NAME));
 
         EpubWriter epubWriter = new EpubWriter();
         String savePath = StrUtil.format("{}/{}.epub", saveDir.getParent(), b.getBookName());
diff --git a/src/main/java/com/pcdd/sonovel/parse/BookParser.java b/src/main/java/com/pcdd/sonovel/parse/BookParser.java
index bdfeede..9138a80 100644
--- a/src/main/java/com/pcdd/sonovel/parse/BookParser.java
+++ b/src/main/java/com/pcdd/sonovel/parse/BookParser.java
@@ -29,6 +29,7 @@
 public class BookParser extends Source {
 
     private static final int TIMEOUT_MILLS = 15_000;
+    public static final String CONTENT = "content";
 
     public BookParser(int sourceId) {
         super(sourceId);
@@ -41,9 +42,9 @@ public Book parse(String url) {
                 .timeout(TIMEOUT_MILLS)
                 .header(Header.USER_AGENT.getValue(), RandomUA.generate())
                 .get();
-        String bookName = document.select(r.getBookName()).attr("content");
-        String author = document.select(r.getAuthor()).attr("content");
-        String intro = document.select(r.getIntro()).attr("content");
+        String bookName = document.select(r.getBookName()).attr(CONTENT);
+        String author = document.select(r.getAuthor()).attr(CONTENT);
+        String intro = document.select(r.getIntro()).attr(CONTENT);
         intro = StrUtil.cleanBlank(intro);
         String coverUrl = document.select(r.getCoverUrl()).attr("src");
 
diff --git a/src/main/java/com/pcdd/sonovel/parse/ChapterParser.java b/src/main/java/com/pcdd/sonovel/parse/ChapterParser.java
index 1e90c6d..00b1f6f 100644
--- a/src/main/java/com/pcdd/sonovel/parse/ChapterParser.java
+++ b/src/main/java/com/pcdd/sonovel/parse/ChapterParser.java
@@ -8,6 +8,7 @@
 import com.pcdd.sonovel.model.ConfigBean;
 import com.pcdd.sonovel.model.SearchResult;
 import com.pcdd.sonovel.util.CrawlUtils;
+import com.pcdd.sonovel.util.ExceptionUtils;
 import com.pcdd.sonovel.util.RandomUA;
 import org.jsoup.Jsoup;
 import org.jsoup.nodes.Document;
@@ -38,6 +39,7 @@ public ChapterParser(ConfigBean config) {
     public Chapter parse(Chapter chapter, CountDownLatch latch, SearchResult sr) {
         try {
             Console.log("<== 正在下载: 【{}】", chapter.getTitle());
+            ExceptionUtils.randomThrow();
             chapter.setContent(crawl(chapter.getUrl(), false));
             latch.countDown();
             return chapterConverter.convert(chapter, config.getExtName());
@@ -50,7 +52,7 @@ public Chapter parse(Chapter chapter, CountDownLatch latch, SearchResult sr) {
     private Chapter retry(Chapter chapter, CountDownLatch latch, SearchResult sr) {
         for (int attempt = 1; attempt <= config.getMaxRetryAttempts(); attempt++) {
             try {
-                Console.log("==> 正在重试下载失败章节: 【{}】，尝试次数: {}/{}", chapter.getTitle(), attempt, config.getMaxRetryAttempts());
+                Console.log("==> 章节下载失败，正在重试: 【{}】，尝试次数: {}/{}", chapter.getTitle(), attempt, config.getMaxRetryAttempts());
                 chapter.setContent(crawl(chapter.getUrl(), true));
                 Console.log("<== 重试成功: 【{}】", chapter.getTitle());
                 latch.countDown();
@@ -107,9 +109,10 @@ private void saveErrorLog(Chapter chapter, SearchResult sr, String errMsg) {
         try (PrintWriter pw = new PrintWriter(new FileWriter(path, true))) {
             // 自带换行符
             pw.println(line);
+
         } catch (IOException e) {
-            throw new RuntimeException(e);
+            Console.error(e);
         }
     }
 
-}
+}
\ No newline at end of file
diff --git a/src/main/java/com/pcdd/sonovel/util/CrawlUtils.java b/src/main/java/com/pcdd/sonovel/util/CrawlUtils.java
index 723a7bd..4eb8c1f 100644
--- a/src/main/java/com/pcdd/sonovel/util/CrawlUtils.java
+++ b/src/main/java/com/pcdd/sonovel/util/CrawlUtils.java
@@ -54,7 +54,7 @@ public Connection.Method buildMethod(String method) {
             case "head" -> Connection.Method.HEAD;
             case "options" -> Connection.Method.OPTIONS;
             case "trace" -> Connection.Method.TRACE;
-            default -> Connection.Method.POST;
+            default -> throw new IllegalArgumentException("Unsupported request method: " + method);
         };
     }
 
diff --git a/src/main/java/com/pcdd/sonovel/util/ExceptionUtils.java b/src/main/java/com/pcdd/sonovel/util/ExceptionUtils.java
index 01f4f23..a24d5b8 100644
--- a/src/main/java/com/pcdd/sonovel/util/ExceptionUtils.java
+++ b/src/main/java/com/pcdd/sonovel/util/ExceptionUtils.java
@@ -11,7 +11,9 @@ public class ExceptionUtils {
 
     // 随机抛异常，测试用
     public void randomThrow() {
-        int i = System.currentTimeMillis() % 2 == 0 ? 0 : 1 / 0;
+        if (System.currentTimeMillis() % 2 == 0) {
+            throw new NullPointerException("随机抛 NPE");
+        }
     }
 
-}
+}
\ No newline at end of file
diff --git a/src/main/java/com/pcdd/sonovel/util/FileUtils.java b/src/main/java/com/pcdd/sonovel/util/FileUtils.java
index 15f9c2f..73cea38 100644
--- a/src/main/java/com/pcdd/sonovel/util/FileUtils.java
+++ b/src/main/java/com/pcdd/sonovel/util/FileUtils.java
@@ -5,6 +5,7 @@
 import java.io.File;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * @author pcdd
@@ -15,7 +16,7 @@ public class FileUtils {
 
     // 文件排序，按文件名升序
     public List<File> sortFilesByName(File dir) {
-        return Arrays.stream(dir.listFiles())
+        return Arrays.stream(Objects.requireNonNull(dir.listFiles()))
                 .sorted((o1, o2) -> {
                     String s1 = o1.getName();
                     String s2 = o2.getName();