我还是Java新手。我在使用Java语法时遇到了一些问题。 我的程序应执行以下步骤：
1）它需要一个csv文件作为输入。
2）它需要一个excel文件作为输入。
3）它应该遍历写入日期的两个文件的第一列。
4）通过添加csv表中的信息来更新excel文件并保存其更改。
我有两个输入示例，以及结果excel表格的外观。
两个输入文件：
export-csv-input.csv
export-excel-input.xlsx
更新后的excel文件应如下所示：
export-excel-output.xlsx
还没有我的Java代码：
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.Reader;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVRecord;
import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.DataFormatter;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
public class CsvToExcelConverter {
public static final String SAMPLE_XLSX_FILE_PATH =
"C:/Users/blawand/Desktop/CSV_to_Excel/export-excel-test.xlsx";
public static final String SAMPLE_CSV_FILE_PATH =
"C:/Users/blawand/Desktop/CSV_to_Excel/export-csv-test.csv";
public static List<String> dates_csv = new ArrayList<>();
public static List<String> dates_excel = new ArrayList<>();
public static void main(String[] args) throws IOException,
InvalidFormatException {
try (Reader reader =
Files.newBufferedReader(Paths.get(SAMPLE_CSV_FILE_PATH));
CSVParser csvParser = new CSVParser(reader, CSVFormat.DEFAULT);)
{
for (CSVRecord csvRecord : csvParser) {
// Accessing Values by Column Index
String name = csvRecord.get(0);
dates_csv.add(name);
}
dates_csv.remove(0);
}
FileInputStream fsIP = new FileInputStream(new
File(SAMPLE_XLSX_FILE_PATH));
/*
* ==================================================================
Iterating over all the
* rows and columns in a Sheet (Multiple ways)
* ==================================================================
*/
// Getting the Sheet at index zero
XSSFWorkbook workbook = new XSSFWorkbook(fsIP);
XSSFSheet sheet = workbook.getSheetAt(0);
// Get the Cell at index 2 from the above row
// Cell cell1 = sheet.getRow(1).getCell(0);
// for (int i = 0; i < dates_excel.size(); i++) {
// XSSFRow rowtest = sheet.createRow((short) i + 1);
// rowtest.createCell(0).setCellValue(dates_csv.get(i));
//
// }
// cell1.setCellValue(dates_csv.get(0));
// Create a DataFormatter to format and get each cell's value as
String
DataFormatter dataFormatter = new DataFormatter();
for (int rowIndex = 1; rowIndex <= sheet.getLastRowNum(); rowIndex++)
{
Row row = sheet.getRow(rowIndex);
if (row != null) {
Cell cell = row.getCell(0); // getColumn(0)
if (cell != null) {
// Found column and there is value in the cell.
// String cellValueMaybeNull = cell.getStringCellValue();
String cellValueMaybeNull =
dataFormatter.formatCellValue(cell);
// String to number set
dates_excel.add(cellValueMaybeNull);
}
}
}
System.out.println(dates_csv);
System.out.println(dates_csv.size());
System.out.println(dates_excel);
System.out.println(dates_excel.size());
while (dates_excel == dates_excel) {
System.out.println("Yes");
break;
}
fsIP.close();
FileOutputStream output_file = new FileOutputStream(new
File(SAMPLE_XLSX_FILE_PATH));
workbook.write(output_file);
output_file.close();
}
}
我已经阅读了两个文件，但是在更新excel文件以及将项目名称添加到正确的日期时遇到了问题。并且如果同一日期已在csv表中写入两次或多次。
您还想知道哪些信息？
感谢您的每一个帮助或建议！
答案 0 :(得分：3)
我为您提供了一个示例，其中大部分通过代码注释进行了解释。尽管如此，该代码基本上执行以下操作：
在构造函数中获取xlsx和csv文件的文件路径。
更新时，它首先将csv文件的内容读入Map作为键，将LocalDate作为值的List<String>。
然后，它遍历工作簿的各行，跳过标题行，并将第一列中的日期与Map<LocalDate, List<String>>的键进行比较。如果映射包含该键，它将开始检查该行中的单元格是否存在当前值，并将它们保留在列表中，以便以后不再写入。
然后，它将开始将值和关键日期写入行的单元格中。
我希望这会有所帮助。
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.time.Instant;
import java.time.LocalDate;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
public class CsvXlsxUpdater {
private static final DateTimeFormatter DATE_TIME_FORMATTER_CSV = DateTimeFormatter.ofPattern("dd.MM.yyyy");
private Path csvFilePath;
private Path xlsxFilePath;
private XSSFWorkbook workbook;
private XSSFSheet sheet;
private Map<LocalDate, List<String>> csvContent = new TreeMap<LocalDate, List<String>>();
private ZoneId zoneId = ZoneId.systemDefault();
public CsvXlsxUpdater(String pathToCsvFile, String pathToXlsxFile) {
csvFilePath = Paths.get(pathToCsvFile);
xlsxFilePath = Paths.get(pathToXlsxFile);
}
/**
* Reads the content of the csv file into the corresponding class variable,
* which is a {@link TreeMap} that has a {@link LocalDate} as key and a
* {@link List<String>} as values.
*/
private void readCsvContent() {
List<String> csvLines;
try {
csvLines = Files.readAllLines(csvFilePath);
for (int i = 1; i < csvLines.size(); i++) {
String line = csvLines.get(i);
String[] splitValues = line.split(",");
if (splitValues.length > 1) {
List<String> lineValues = Arrays.asList(splitValues);
List<String> projects = getProjectValuesFrom(lineValues);
LocalDate localDate = LocalDate.parse(lineValues.get(0), DATE_TIME_FORMATTER_CSV);
if (csvContent.containsKey(localDate)) {
projects.forEach((String project) -> {
List<String> csvProjects = csvContent.get(localDate);
if (!csvProjects.contains(project)) {
csvProjects.add(project);
}
});
} else {
csvContent.put(localDate, projects);
}
} else {
LocalDate localDate = LocalDate.parse(splitValues[0], DATE_TIME_FORMATTER_CSV);
csvContent.put(localDate, new ArrayList<String>());
}
}
} catch (IOException e) {
System.err.println("CANNOT FIND OR READ CSV FILE: " + e.getMessage());
e.printStackTrace();
} catch (UnsupportedOperationException e) {
System.err.println("UNSUPPORTED OPERATION: " + e.getMessage());
e.printStackTrace();
}
}
/**
* Gets the corresponding {@link LocalDate} from a given (and deprecated)
* {@link Date}
*
* @param date the deprecated {@link Date} object
* @return the corresponding {@link LocalDate}
*/
private LocalDate parseLocalDateFrom(Date date) {
Instant instantDate = date.toInstant();
return instantDate.atZone(zoneId).toLocalDate();
}
/**
* Takes a list of read values from the csv file and returns a list containing
* all the values of the given list <strong>except from the first
* element</strong>, which is a {@link String} representation of a date and
* should be treated differently in this context.
*
* @param values the original list of {@link String}s
* @return another list without the first element of the given list
*/
private List<String> getProjectValuesFrom(List<String> values) {
List<String> projectValues = new ArrayList<String>();
for (int i = 1; i < values.size(); i++) {
String value = values.get(i);
if (!value.equals("")) {
projectValues.add(value);
}
}
return projectValues;
}
/**
* Updates the workbook with the values read from the csv file
*/
public void updateWorkbook() {
readCsvContent();
try {
FileInputStream fis = new FileInputStream(xlsxFilePath.toAbsolutePath().toString());
workbook = new XSSFWorkbook(fis);
sheet = workbook.getSheetAt(0);
// iterate over the rows
Iterator<Row> rowIterator = sheet.rowIterator();
while (rowIterator.hasNext()) {
XSSFRow row = (XSSFRow) rowIterator.next();
if (row.getRowNum() == 0) {
// skip this or set updated headers
} else {
// check if the csvContent contains the value of cell(0)
LocalDate dateKey = parseLocalDateFrom(row.getCell(0).getDateCellValue());
if (csvContent.containsKey(dateKey)) {
// if yes, get list-value of the key
List<String> values = csvContent.get(dateKey);
// check if there are values
if (values != null) {
if (values.size() > 0) {
// if there are, then go checking the cell values
List<String> projectsInXlsx = new ArrayList<String>();
Iterator<Cell> cellIterator = row.cellIterator();
int lastColumnIndex = 1;
// go through all cells with a value except from the first one
while (cellIterator.hasNext()) {
Cell cell = cellIterator.next();
// skip the first column as it contains the date
if (cell.getColumnIndex() != 0) {
lastColumnIndex = cell.getColumnIndex();
System.out.println("Accessing cell in column " + lastColumnIndex);
// if there is a cell with a value
if (cell.getStringCellValue() != null) {
if (!cell.getStringCellValue().equals("")) {
// check if the value in the cell is also in the csv values
if (values.contains(cell.getStringCellValue())) {
projectsInXlsx.add(cell.getStringCellValue());
lastColumnIndex++;
}
}
}
}
}
// now go through the values of the csv file
int offset = 0; // cell column offset for more than one entry per date
for (String value : values) {
if (!projectsInXlsx.contains(value)) {
// create a cell after the last one with a value
row.createCell(lastColumnIndex + offset).setCellValue(value);
offset++;
}
}
}
}
}
}
}
fis.close();
FileOutputStream fileOutputStream = new FileOutputStream(xlsxFilePath.toAbsolutePath().toString());
workbook.write(fileOutputStream);
fileOutputStream.flush();
fileOutputStream.close();
workbook.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
在main方法中，您只需要调用构造函数，将文件路径作为String传递，然后调用updateWorkbook()方法，因为它首先在内部读取csv
示例：
public class CsvXlsxMain {
private static final String CSV_FILE_PATH = "S:\\ome\\example\\path\\to\\csv-input.csv";
private static final String XLSX_FILE_PATH = "S:\\ome\\example\\path\\to\\excel-input.xlsx";
public static void main(String[] args) {
CsvXlsxUpdater cxu = new CsvXlsxUpdater(CSV_FILE_PATH, XLSX_FILE_PATH);
cxu.updateWorkbook();
}
}
请记住，此代码尚未经过完整测试，以后可能会出现备用资源问题 如果需要，可以使用各种符合您要求的xlsx和csv输入进行测试。
我还没有使用任何库来解析csv文件！
我希望这对您有所帮助...