我在写入输出流时收到java.lang.NullPointerException：
workbook.write(new FileOutputStream("test1.xslx"));
例外是：
Exception:
java.lang.NullPointerException
at org.apache.poi.POIXMLDocument.write(POIXMLDocument.java:201)
at ExcelCompare.WriteOutputIntoExcel.addRow(WriteExcel.java:124)
at ExcelCompare.CompareExcel.main(MainClassExcelCompare.java:113)
这里我有两个课程：CompareExcel课程和WriteOutputIntoExcel
我想比较两张Excel工作表Excel1.xslx和Excel2.xslx，并将结果重新放回Result.xslx。
我不希望将所有内容都放在Result.xslx中，我只想在Excel1和Excel2.中放置不匹配的行
这是Main类
package ExcelCompare;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Iterator;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.IndexedColors;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
public class CompareExcel {
public static void main(String[] args) {
try {
int temp;
File excel1 = new File("C://Users/ckothakapax076037/Desktop/Demo1.xlsx");
FileInputStream fis1 = new FileInputStream(excel1);
XSSFWorkbook book1 = new XSSFWorkbook(fis1);
XSSFSheet sheet1 = book1.getSheetAt(0);
File excel2 = new File("C://Users/ckothakapax076037/Desktop/Demo2.xlsx");
FileInputStream fis2 = new FileInputStream(excel2);
XSSFWorkbook book2 = new XSSFWorkbook(fis2);
XSSFSheet sheet2 = book2.getSheetAt(0);
WriteExcel obj1 = new WriteExcel();
obj1.setOutputFile("C://Users/ckothakapax076037/Desktop/Result.xlsx");
//Get iterator to all the rows in current sheet
Iterator<Row> itr1 = sheet1.iterator();
Iterator<Row> itr2 = sheet2.iterator();
// Iterating through all cells row by row
while (itr1.hasNext() && itr2.hasNext()) {
temp = 0;
int j = 0;
Row row1 = itr1.next();
Row row2 = itr2.next();
//Get iterator to all cells of current row
Iterator<Cell> cellIterator1 = row1.cellIterator();
Iterator<Cell> cellIterator2 = row2.cellIterator();
CellStyle style = book1.createCellStyle();
style = book1.createCellStyle();
style.setFillForegroundColor(IndexedColors.RED.getIndex());
style.setFillPattern(CellStyle.SOLID_FOREGROUND);
while (cellIterator1.hasNext() && cellIterator2.hasNext()) {
Cell cell1 = cellIterator1.next();
Cell cell2 = cellIterator2.next();
switch (cell1.getCellType()) {
case Cell.CELL_TYPE_STRING:
System.out.print(cell1.getStringCellValue() + "\t");
System.out.print(cell2.getStringCellValue() + "\t");
if (!cell1.getStringCellValue().equalsIgnoreCase(cell2.getStringCellValue())) {
temp++;
cell1.setCellStyle(style);
}
break;
case Cell.CELL_TYPE_NUMERIC:
System.out.print(cell1.getNumericCellValue() + "\t");
System.out.print(cell2.getNumericCellValue() + "\t");
if (cell1.getNumericCellValue() != cell2.getNumericCellValue()) {
temp++;
cell1.setCellStyle(style);
}
break;
case Cell.CELL_TYPE_BOOLEAN:
System.out.print(cell1.getBooleanCellValue() + "\t");
System.out.print(cell2.getBooleanCellValue() + "\t");
break;
case Cell.CELL_TYPE_BLANK:
System.out.print(cell1.getNumericCellValue() + "\t");
System.out.print(cell2.getNumericCellValue() + "\t");
if (cell2.getStringCellValue() != " ") {
temp++;
cell1.setCellStyle(style);
}
break;
default:
}
j++;
}
System.out.print("\n");
System.out.print("Flag value:" + temp);
System.out.print("\n");
if (temp >= 1) {
obj1.addRow(row1.cellIterator(), row2.cellIterator());
}
}
book1.close();
fis1.close();
book2.close();
fis2.close();
obj1.closerActivity();
} catch (FileNotFoundException fe) {
fe.printStackTrace();
} catch (IOException ie) {
ie.printStackTrace();
} catch (Exception ee) {
ee.printStackTrace();
}
}
}
现在我有WriteOutputIntoExcel类将结果放回Result.xslx
package ExcelCompare;
import java.io.FileOutputStream;
import java.util.Iterator;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.IndexedColors;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
public class WriteOutputIntoExcel {
private static String OutputFile;
private static XSSFWorkbook myWorkBook = new XSSFWorkbook();
private static XSSFSheet mySheet = myWorkBook.createSheet("Report");
public static int i = 0;
public void setOutputFile(String OutputFile1) {
OutputFile = OutputFile1;
}
public void addRow(Iterator<Cell> cellIterator1, Iterator<Cell> cellIterator2) {
try {
XSSFRow row = mySheet.createRow(i++);
CellStyle style = myWorkBook.createCellStyle();
style = myWorkBook.createCellStyle();
style.setFillForegroundColor(IndexedColors.RED.getIndex());
style.setFillPattern(CellStyle.SOLID_FOREGROUND);
FileOutputStream out = new FileOutputStream(OutputFile);
System.out.print("Writing result from Sheet1");
System.out.print("\n");
while (cellIterator1.hasNext()) {
int j = 0;
Cell cell1 = cellIterator1.next();
switch (cell1.getCellType()) {
case Cell.CELL_TYPE_STRING:
System.out.print(cell1.getStringCellValue() + "\t");
row.createCell(j).setCellValue(cell1.getStringCellValue());
row.createCell(j).setCellStyle(style);
break;
case Cell.CELL_TYPE_NUMERIC:
System.out.print(cell1.getNumericCellValue() + "\t");
row.createCell(j).setCellValue(cell1.getNumericCellValue());
row.createCell(j).setCellStyle(style);
break;
case Cell.CELL_TYPE_BLANK:
System.out.print(cell1.getStringCellValue() + "\t");
row.createCell(j).setCellValue(cell1.getStringCellValue());
row.createCell(j).setCellStyle(style);
break;
default:
System.out.print(cell1.getStringCellValue() + "\t");
row.createCell(j).setCellValue(cell1.getStringCellValue());
row.createCell(j).setCellStyle(style);
}
j++;
}
System.out.print("\n");
System.out.print("Writing result from Sheet2");
System.out.print("\n");
while (cellIterator2.hasNext()) {
int j = 0;
Cell cell2 = cellIterator2.next();
switch (cell2.getCellType()) {
case Cell.CELL_TYPE_STRING:
System.out.print(cell2.getStringCellValue() + "\t");
row.createCell(j).setCellValue(cell2.getStringCellValue());
break;
case Cell.CELL_TYPE_NUMERIC:
System.out.print(cell2.getNumericCellValue() + "\t");
row.createCell(j).setCellValue(cell2.getNumericCellValue());
break;
case Cell.CELL_TYPE_BLANK:
System.out.print(cell2.getStringCellValue() + "\t");
row.createCell(j).setCellValue(cell2.getStringCellValue());
break;
default:
System.out.print(cell2.getStringCellValue() + "\t");
row.createCell(j).setCellValue(cell2.getStringCellValue());
}
j++;
}
System.out.print("\n");
myWorkBook.write(out);
out.close();
myWorkBook.close();
} catch (Exception e) {
e.printStackTrace();
}
}
public void closerActivity() {
try {
System.out.println(" Hi i am in close");
} catch (Exception e) {
e.printStackTrace();
}
}
}
我还想突出显示Excel1中与Excel2不同的单元格。
请帮助我实现这一目标。
答案 0 :(得分：0)
解决此类问题的最佳方法是将库的源代码（在本例中为POI）附加到IDE，这样您就可以快速查找库中第201行的内容。请注意，您需要确保库lib版本与src版本相同，否则您可以查看错误的行。
好的，很可能你的addRow参数之一是null（迭代器）。所以先检查一下（println）。