ADD file via upload

ExcelExporter.java

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+// src/main/java/com/llm/analysis/ExcelExporter.java
+package com.llm.analysis;
+
+import org.apache.poi.ss.usermodel.*;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+
+public class ExcelExporter {
+
+    /**
+     * 将词频统计结果写入XLSX文件。
+     * @param topWords Top N 词语列表
+     * @param filename 输出文件名
+     */
+    public static void exportToXLSX(List<Map.Entry<String, Long>> topWords, String filename) {
+        Workbook workbook = new XSSFWorkbook();
+        Sheet sheet = workbook.createSheet("LLM应用案例词频");
+
+        // 创建表头
+        Row headerRow = sheet.createRow(0);
+        headerRow.createCell(0).setCellValue("排名");
+        headerRow.createCell(1).setCellValue("词语/LLM应用案例");
+        headerRow.createCell(2).setCellValue("词频 (总数)");
+
+        // 填充数据
+        int rowNum = 1;
+        for (int i = 0; i < topWords.size(); i++) {
+            Map.Entry<String, Long> entry = topWords.get(i);
+            Row row = sheet.createRow(rowNum++);
+            
+            row.createCell(0).setCellValue(i + 1); // 排名
+            row.createCell(1).setCellValue(entry.getKey()); // 词语
+            row.createCell(2).setCellValue(entry.getValue()); // 词频
+        }
+
+        // 自动调整列宽
+        for (int i = 0; i < 3; i++) {
+            sheet.autoSizeColumn(i);
+        }
+
+        // 写入文件
+        try (FileOutputStream fileOut = new FileOutputStream(filename)) {
+            workbook.write(fileOut);
+            System.out.println("✅ 数据成功导出到 " + filename);
+        } catch (IOException e) {
+            System.err.println("导出Excel失败：" + e.getMessage());
+        } finally {
+            try {
+                workbook.close();
+            } catch (IOException e) {
+                // Ignore
+            }
+        }
+    }
+}