Java-从excel中删除重复项

Question

我发现这个代码在线并试图运行它。但它是给予和Null指针错误。有人可以帮忙解决这个问题吗？谢谢

错误是说：java.lang.NullPointerException     在LearnJava.compareText.main（compareText.java:79）

package test;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.apache.poi.ss.usermodel.Cell;

public class Removeduplicate {


public static void main(String[] args) {
    HSSFWorkbook workbook_Output;
    HSSFWorkbook workbook_Output_Dup;
    HSSFWorkbook workbook_Output_Final;
    HSSFWorkbook workbook_Output_Final_2=null;

    HSSFSheet sheet_Output;
    HSSFSheet sheet_Output_Dup;
    HSSFSheet sheet_Output_Final;

    HSSFRow row_Output;
    HSSFRow row_Output_Dup;
    HSSFRow row_Output_Final;

    HSSFCell cell;

    HSSFRow row_Output_dup;
//  Set<Integer> markrowdup = new HashSet<Integer>();
    //List<HSSFCell> cellStoreList=new ArrayList<HSSFCell>();

    try {
        FileInputStream fistream_Output= new FileInputStream("C:\\Users\\Satya\\Desktop\\Output.xls");
        workbook_Output = new HSSFWorkbook(new POIFSFileSystem(fistream_Output));

        File file_dup = new File("C:\\Users\\Satya\\Desktop\\Output_Dup.xls");
        FileOutputStream fistream_output_dup = new FileOutputStream(file_dup);
        workbook_Output.write(fistream_output_dup);
        fistream_output_dup.close();

        FileInputStream fistream_Output_Dup= new FileInputStream("C:\\Users\\Satya\\Desktop\\Output_Dup.xls");
        workbook_Output_Dup = new HSSFWorkbook(fistream_Output_Dup);

        //File file_final_2 = new File("C:\\Users\\Satya\\Desktop\\Output_CRQ.xls");



        for (int sheetnum = 0; sheetnum < workbook_Output.getNumberOfSheets(); sheetnum++) {

            Set<Integer> markrowdup = new HashSet<Integer>();
            List<HSSFCell> cellStoreList=new ArrayList<HSSFCell>();

        sheet_Output_Dup = workbook_Output_Dup.getSheetAt(sheetnum);
        sheet_Output = workbook_Output.getSheetAt(sheetnum);

        int lastrow = sheet_Output.getLastRowNum();
        for (int i = 1; i <= lastrow; i++) {
            row_Output_Dup = sheet_Output_Dup.getRow(i);
            row_Output = sheet_Output.getRow(i);

            for (int j = i; j <= lastrow; j++) {
                row_Output_dup = sheet_Output.getRow(j);
                if(i!=j)
                {
                if(row_Output.getCell(1).getStringCellValue()==row_Output_dup.getCell(1).getStringCellValue())
                {
                    markrowdup.add(j);
                    System.out.println(row_Output.getCell(1).getStringCellValue()+" : Duplicte row num: "+j);

                }
                }

            }
            }
        Object[] o = markrowdup.toArray();
        Arrays.sort(o);

        for (Object object : o) {
            int row = ((Integer) object).intValue();
            row_Output_Dup=sheet_Output_Dup.getRow(row);
            sheet_Output_Dup.removeRow(row_Output_Dup);
            }
        File file_final = new File("C:\\Users\\Satya\\Desktop\\Output_Final.xls");
        FileOutputStream fostream_final = new FileOutputStream(file_final);
        workbook_Output_Dup.write(fostream_final);
        fostream_final.close();



        FileInputStream fistream_final = new FileInputStream(file_final);
        workbook_Output_Final = new HSSFWorkbook(fistream_final);
        sheet_Output_Final = workbook_Output_Final.getSheetAt(sheetnum);

        for (int i = 0; i <= sheet_Output_Final.getLastRowNum(); i++) {
            row_Output_Final = sheet_Output_Final.getRow(i);
            if(row_Output_Final==null)
                System.out.println("Row is null");
            else
            {
                Iterator<Cell> iterator_output_final = row_Output_Final.cellIterator();
                while (iterator_output_final.hasNext()) {
                     cell = (HSSFCell) iterator_output_final.next();
                     cellStoreList.add(cell);

                }
            }



        }
        Iterator<HSSFCell> iterator_final_data = cellStoreList.iterator();
        File file_final_2 = new File("C:\\Users\\Satya\\Desktop\\Output_CRQ.xls");
        FileOutputStream fostream_final_2 = new FileOutputStream(file_final_2);
        if(workbook_Output_Final_2 == null)
        workbook_Output_Final_2=new  HSSFWorkbook();

        workbook_Output_Final_2.createSheet(workbook_Output.getSheetName(sheetnum));

        HSSFSheet temp = workbook_Output_Final_2.getSheetAt(sheetnum);
        int i=0;
        int temp_row=0;
        HSSFRow row = temp.createRow(temp_row);
        while (iterator_final_data.hasNext()) {

            HSSFCell cell2 = iterator_final_data.next();
            row.createCell(i).setCellValue(cell2.getStringCellValue());
            System.out.print(cell2.getStringCellValue()+":  :");
            i++;
            if(i==4)
                {
                System.out.println();
                i=0;
                temp_row++;
                row = temp.createRow(temp_row);
            }

        }
        workbook_Output_Final_2.write(fostream_final_2);

        //fostream_final_2.close();
        fistream_final.close();
        fistream_Output.close();

        fostream_final_2.flush();
        fostream_final_2.close();

    } 
        fistream_Output.close();
        fistream_Output_Dup.close();

    }
        catch (Exception e) {

        e.printStackTrace();
    }

}

} 

感谢您的帮助。非常感谢