添加 w9 Article 类与 HistoryCommand 练习

w9/Article.java

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+import java.time.LocalDate;
+
+public class Article {
+    private String title;
+    private String content;
+    private String url;
+    private String author;
+    private LocalDate publishDate;
+
+    public Article(String title, String content, String url, String author, LocalDate publishDate) {
+        this.title = title;
+        this.content = content;
+        this.url = url;
+        this.author = author;
+        this.publishDate = publishDate;
+    }
+
+    public String getTitle() { return title; }
+    public void setTitle(String title) { this.title = title; }
+
+    public String getContent() { return content; }
+    public void setContent(String content) { this.content = content; }
+
+    public String getUrl() { return url; }
+    public void setUrl(String url) { this.url = url; }
+
+    public String getAuthor() { return author; }
+    public void setAuthor(String author) { this.author = author; }
+
+    public LocalDate getPublishDate() { return publishDate; }
+    public void setPublishDate(LocalDate publishDate) { this.publishDate = publishDate; }
+
+    @Override
+    public String toString() {
+        return "Article{" +
+                "title='" + title + '\'' +
+                ", author='" + author + '\'' +
+                ", publishDate=" + publishDate +
+                ", url='" + url + '\'' +
+                '}';
+    }
+
+    public static void main(String[] args) {
+        Article article = new Article("Java编程", "内容...", "http://example.com", "张三", LocalDate.of(2024, 1, 15));
+        System.out.println(article);
+    }
+}

w9/HistoryCommand.java

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+import java.util.ArrayList;
+import java.util.List;
+
+public class HistoryCommand {
+    private final List<String> commandHistory = new ArrayList<>();
+
+    public void recordCommand(String command) {
+        if (command != null && !command.isBlank()) {
+            commandHistory.add(command.trim());
+        }
+    }
+
+    public List<String> getHistory() {
+        return new ArrayList<>(commandHistory);
+    }
+
+    public void printHistory() {
+        System.out.println("=== 命令历史 ===");
+        for (int i = 0; i < commandHistory.size(); i++) {
+            System.out.printf("%d: %s%n", i + 1, commandHistory.get(i));
+        }
+    }
+
+    public void clearHistory() {
+        commandHistory.clear();
+    }
+
+    public static void main(String[] args) {
+        HistoryCommand history = new HistoryCommand();
+        history.recordCommand("crawl `https://example.com` ");
+        history.recordCommand("list");
+        history.recordCommand("exit");
+
+        history.printHistory();
+    }
+}

w9/思考题.txt

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+分析  List<Article>  共享引用的风险（200字小结）
+ 
+ List<Article>  的共享引用存在多线程安全与数据一致性风险。当多个模块共享同一个列表引用时，若某模块修改了列表（如增删元素），其他模块读取时会出现并发修改异常或脏数据；若修改了列表内  Article  对象的属性，所有持有该对象引用的模块都会看到变化，引发数据不一致。此外，外部代码可能直接修改列表或对象内部状态，破坏封装性，导致调试困难。解决方式是返回列表副本或不可修改视图，避免共享引用。