feat(w7):W7-孟鑫垚-202506010204

w7/Main.java

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+import java.io.*;
+import java.util.ArrayList;
+import java.util.List;
+
+// =============== 自定义异常类（面向对象体现） ===============
+class InvalidScoreException extends Exception {
+    public InvalidScoreException(String message) {
+        super(message);
+    }
+}
+
+// =============== 成绩处理器类 ===============
+class ScoreProcessor {
+    private List<Integer> scores = new ArrayList<>();
+
+    /**
+     * 从指定文件读取成绩
+     * @param filename 文件名
+     * @throws IOException 文件读取错误
+     * @throws InvalidScoreException 成绩格式无效
+     */
+    public void loadScoresFromFile(String filename) throws IOException, InvalidScoreException {
+        scores.clear();
+        try (BufferedReader reader = new BufferedReader(new FileReader(filename))) {
+            String line;
+            int lineNumber = 0;
+            while ((line = reader.readLine()) != null) {
+                lineNumber++;
+                line = line.trim();
+                if (line.isEmpty()) continue; // 跳过空行
+
+                try {
+                    int score = Integer.parseInt(line);
+                    if (score < 0 || score > 100) {
+                        throw new InvalidScoreException("第 " + lineNumber + " 行：成绩应在 0~100 之间，但得到 " + score);
+                    }
+                    scores.add(score);
+                } catch (NumberFormatException e) {
+                    throw new InvalidScoreException("第 " + lineNumber + " 行：\"" + line + "\" 不是有效的整数");
+                }
+            }
+        }
+    }
+
+    /**
+     * 计算平均分
+     * @return 平均分（保留两位小数）
+     * @throws IllegalStateException 如果没有有效成绩
+     */
+    public double calculateAverage() {
+        if (scores.isEmpty()) {
+            throw new IllegalStateException("没有可计算的有效成绩");
+        }
+        int sum = scores.stream().mapToInt(Integer::intValue).sum();
+        return Math.round((double) sum / scores.size() * 100) / 100.0;
+    }
+
+    public int getScoreCount() {
+        return scores.size();
+    }
+}
+
+// =============== 主类 ===============
+public class Main {
+    public static void main(String[] args) {
+        ScoreProcessor processor = new ScoreProcessor();
+
+        try {
+            processor.loadScoresFromFile("scores.txt");
+            double average = processor.calculateAverage();
+            System.out.printf("共读取 %d 条有效成绩，平均分：%.2f%n",
+                    processor.getScoreCount(), average);
+        } catch (FileNotFoundException e) {
+            System.err.println("❌ 文件未找到：请确保 'scores.txt' 存在于当前目录。");
+        } catch (IOException e) {
+            System.err.println("❌ 读取文件时发生 I/O 错误：" + e.getMessage());
+        } catch (InvalidScoreException e) {
+            System.err.println("❌ 成绩数据格式错误：" + e.getMessage());
+        } catch (IllegalStateException e) {
+            System.err.println("❌ 数据不足：" + e.getMessage());
+        }
+    }
+}