【Apache POI库读取Excel文件，并使用HashMap来存储和检查重复项】

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.FileInputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

public class ExcelDuplicateFinder {

    public static void main(String[] args) {
        String filePath = "path/to/your/excel/file.xlsx";
        String sheetName = "Sheet1";

        try (FileInputStream fis = new FileInputStream(filePath);
             Workbook workbook = new XSSFWorkbook(fis)) {

            Sheet sheet = workbook.getSheet(sheetName);
            if (sheet == null) {
                System.out.println("Sheet '" + sheetName + "' not found.");
                return;
            }

            Map<String, Integer> dataMap = new HashMap<>();
            int rowCount = sheet.getLastRowNum() + 1;

            for (int i = 0; i < rowCount; i++) {
                Row row = sheet.getRow(i);
                if (row != null) {
                    Cell cell = row.getCell(0); // Assuming data is in the first column
                    if (cell != null) {
                        String data = cell.getStringCellValue();
                        if (dataMap.containsKey(data)) {
                            System.out.println("Duplicate data found: " + data);
                        } else {
                            dataMap.put(data, i);
                        }
                    }
                }
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}