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Unable to open Excel file after excecuting my java apache poi program and i am using file output stream

I am using Apache poi to extract Mysql data to an Excel file. The code is running correctly but when I am trying to open the excel file it is showing error.
package com.telkomsel.excel;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.HashMap;
import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import com.telkomsel.configuirator.Configurator;
import com.telkomsel.dbconnection.DBConnection;
import com.telkomsel.service.TelkomselEntities;
public class TelkomselExcel {
DBConnection db = new DBConnection();
static Configurator configurator = null;
Connection conn = null;
static Statement statement = null;
static ResultSet resultSet = null;
public static HashMap<Integer, TelkomselEntities> getTelkomselData(Statement statement) {
configurator = new Configurator();
String Query = configurator.getProperty("sql_query1");
HashMap<Integer, TelkomselEntities> all = null;
TelkomselEntities smsModel = null;
try {
all = new HashMap<Integer, TelkomselEntities>();
resultSet = statement.executeQuery(Query);
while (resultSet.next()) {
int hour = resultSet.getInt("hour(timestamp)");
String count = resultSet.getString("count(1)");
smsModel = new TelkomselEntities(hour, count, count, count);
all.put(hour, smsModel);
}
smsModel = new TelkomselEntities();
FileInputStream fis = new FileInputStream(new File("Tracker.xlsx"));
XSSFWorkbook workbook = new XSSFWorkbook(fis);
XSSFSheet worksheet = workbook.getSheetAt(0);
XSSFRow row = null;
XSSFCell cell;
int i = 1;
for (Integer l : all.keySet()) {
TelkomselEntities us = all.get(l);
row = worksheet.createRow(i);
cell = row.createCell(2);
cell.setCellValue(us.getHour());
cell = row.createCell(3);
cell.setCellValue(us.getCharge_Count());
i++;
}
fis.close();
FileOutputStream output_file = new FileOutputStream(new File("Tracker.xlsx"),true);
System.out.println("SUCCESS");
workbook.write(output_file);
workbook.close();
output_file.flush();
output_file.close();
} catch (Exception e) {
System.out.println(e);
}
return all;
}
}
I think file output stream is creating problem as it converts data into byte codes. i tried every thing but doesn't work. my excel file is not working

As you supposed, the problem hides inside the line:
FileOutputStream output_file = new FileOutputStream(new File("Tracker.xlsx"),true);
When creating a new XSSFWorkbook Java Object from an existing excel (which you want to update), that XSSFWorkbook is initially created based on your excel file content, then it is totally independent from it.The proof of this is that all changes to the XSSFWorkbook Java Object ARE NOT going to affect the original excel file at all. Apache Poi works that way!
This is the reason why once you're done editing your XSSFWorkbook you have to save it as a new excel file (using a FileOutputStream) overriding the original one (in a sense, you're now updating your excel file with all your changes).
But as the docs says, you're telling FileOutputStream not to override the original excel file with the new and updated one but to append the second to the first one, upsi dupsi! You're creating a single file which contains both all the bytes of the original old file and all the bytes of the new updated one!
To solve the problem, just use instead:
FileOutputStream output_file = new FileOutputStream(new File("Tracker.xlsx"),false);
or
FileOutputStream output_file = new FileOutputStream(new File("Tracker.xlsx"));
and you're done!
Edit: learn Apache Poi before using Apache Poi
It seems that you're using FileOutputStream wrong because you don't know how Apache Poi works and how to use it. You might want to study a little bit about it before using it, the web is full of examples and tutorials! Here they are some examples provided by Apache Poi itself, you might want to have a look at them.
As I said before, the XSSFWorkbook is initialized with all the content of your original excel file. So if you start filling your XSSFSheet from the second line (that's what you're actually doing with your code) you are literally asking to your XSSFWorkbook to override existing data with new one.
You have to improve your code, searching for already existing data in rows and cells and not overriding it if you don't want to.
Rows and cells of each XSSFSheet of your XSSFWorkbook are numbered using 0-based indexes (that's the reason why your code, which starts filling rows from index 1, is filling rows starting from the second one).
With the method XSSFSheet#getRow(int rownum) you can retreive any row from the current XSSFSheet indicating its 0-based index. If this method returns null, then the row you're asking for has never been used and you have to create it using the method XSSFSheet#createRow(int rownum). If it doesn't, then the row you're asking for has already been used and contains some data in some of its cells.
With the method XSSFRow#getCell(int cellnum) you can retrieve any cell from the current XSSFRow indicating its 0-based index. If this method returns null, then the cell you're asking for has never been used and you have to create it using the method XSSFRow#createCell(int cellnum, CellType celltype). If it doesn't, then the cell you're asking for has already been used and contains some data in it.
You can retrieve the CellType of an existing XSSFCell with the method XSSFCell#getCellType().
You can retreive the content of an existing XSSFCell (on the basis of its CellType) using such methods as XSSFCell#getStringCellValue(), XSSFCell#getNumericCellValue() or XSSFCell#getBooleanCellValue().
Other useful methods are XSSFSheet#getLastRowNum() and XSSFRow#getLastCellNum(). The first one returns the index of the last already used row inside your sheet, the second one returns the index of the first not used cell inside your row.
Here it is an example for you (filling 42 rows of your sheet after the last existing one):
public static void main(String[] args) throws EncryptedDocumentException, FileNotFoundException, IOException {
// Step 1: load your excel file as a Workbook
String excelFilePath = "D:\\Desktop\\textExcel.xlsx";
XSSFWorkbook workbook = (XSSFWorkbook) WorkbookFactory.create(new FileInputStream(excelFilePath));
// Step 2: modify your Workbook as you prefer
XSSFSheet sheet = workbook.getSheetAt(0);
int firstUnusedRowIndex = sheet.getLastRowNum() + 1;
for (int rowIndex = firstUnusedRowIndex ; rowIndex < firstUnusedRowIndex + 42 ; rowIndex++) {
sheet.createRow(rowIndex).createCell(0, CellType.STRING).setCellValue("New Row n°" + (rowIndex - firstUnusedRowIndex + 1));
}
// Step 3: update the original excel file
FileOutputStream outputStream = new FileOutputStream(excelFilePath);
workbook.write(outputStream);
workbook.close();
outputStream.close();
}

Java Apache POI Excel save as PDF

How can I convert/save excel file to pdf? I'm using java play framework to generate some excel files and now the requirement changes to pdf. I don't want to recode everything.
Is there a way to convert to pdf?
The excel files I'm generating are from a template; I read the excel template file, write changes, and save as new excel file. That way, the template is unchanged. It contains border, image, and other formatting.

You would need the following Java libraries and associated JAR files for the program to work.
POI v3.8
iText v5.3.4
Try this Example to convert XLS to PDF
The complete Java code that accepts Excel spreadsheet data as an input and transforms that to a PDF table data is provided below:
import java.io.FileInputStream;
import java.io.*;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.ss.usermodel.*;
import java.util.Iterator;
import com.itextpdf.text.*;
import com.itextpdf.text.pdf.*;
public class excel2pdf {
public static void main(String[] args) throws Exception{
FileInputStream input_document = new FileInputStream(new File("C:\\excel_to_pdf.xls"));
// Read workbook into HSSFWorkbook
HSSFWorkbook my_xls_workbook = new HSSFWorkbook(input_document);
// Read worksheet into HSSFSheet
HSSFSheet my_worksheet = my_xls_workbook.getSheetAt(0);
// To iterate over the rows
Iterator<Row> rowIterator = my_worksheet.iterator();
//We will create output PDF document objects at this point
Document iText_xls_2_pdf = new Document();
PdfWriter.getInstance(iText_xls_2_pdf, new FileOutputStream("Excel2PDF_Output.pdf"));
iText_xls_2_pdf.open();
//we have two columns in the Excel sheet, so we create a PDF table with two columns
//Note: There are ways to make this dynamic in nature, if you want to.
PdfPTable my_table = new PdfPTable(2);
//We will use the object below to dynamically add new data to the table
PdfPCell table_cell;
//Loop through rows.
while(rowIterator.hasNext()) {
Row row = rowIterator.next();
Iterator<Cell> cellIterator = row.cellIterator();
while(cellIterator.hasNext()) {
Cell cell = cellIterator.next(); //Fetch CELL
switch(cell.getCellType()) { //Identify CELL type
//you need to add more code here based on
//your requirement / transformations
case Cell.CELL_TYPE_STRING:
//Push the data from Excel to PDF Cell
table_cell=new PdfPCell(new Phrase(cell.getStringCellValue()));
//feel free to move the code below to suit to your needs
my_table.addCell(table_cell);
break;
}
//next line
}
}
//Finally add the table to PDF document
iText_xls_2_pdf.add(my_table);
iText_xls_2_pdf.close();
//we created our pdf file..
input_document.close(); //close xls
}
}
i hope this will help you

Add on to assylias's answer
The code from assylias above was very helpful to me in solving this problem. The answer from santhosh could be great if you don't care about the resulting PDF looking exactly like your excel pdf export would look. However, if you are, say, filling out an excel template using Apache POI an then trying to export that while preserving its look and not writing a ton of code in iText just to try to get close to that look, then the VBS option is quite nice.
I'll share a Java version of the kotlin assylias has above in case that helps anyone. All credit to assylias for the general form of the solution.
In Java:
try {
//create a temporary file and grab the path for it
Path tempScript = Files.createTempFile("script", ".vbs");
//read all the lines of the .vbs script into memory as a list
//here we pull from the resources of a Gradle build, where the vbs script is stored
System.out.println("Path for vbs script is: '" + Main.class.getResource("xl2pdf.vbs").toString().substring(6) + "'");
List<String> script = Files.readAllLines(Paths.get(Main.class.getResource("xl2pdf.vbs").toString().substring(6)));
// append test.xlsm for file name. savePath was passed to this function
String templateFile = savePath + "\\test.xlsm";
templateFile = templateFile.replace("\\", "\\\\");
String pdfFile = savePath + "\\test.pdf";
pdfFile = pdfFile.replace("\\", "\\\\");
System.out.println("templateFile is: " + templateFile);
System.out.println("pdfFile is: " + pdfFile);
//replace the placeholders in the vbs script with the chosen file paths
for (int i = 0; i < script.size(); i++) {
script.set(i, script.get(i).replaceAll("XL_FILE", templateFile));
script.set(i, script.get(i).replaceAll("PDF_FILE", pdfFile));
System.out.println("Line " + i + " is: " + script.get(i));
}
//write the modified code to the temporary script
Files.write(tempScript, script);
//create a processBuilder for starting an operating system process
ProcessBuilder pb = new ProcessBuilder("wscript", tempScript.toString());
//start the process on the operating system
Process process = pb.start();
//tell the process how long to wait for timeout
Boolean success = process.waitFor(timeout, minutes);
if(!success) {
System.out.println("Error: Could not print PDF within " + timeout + minutes);
} else {
System.out.println("Process to run visual basic script for pdf conversion succeeded.");
}
} catch (Exception e) {
e.printStackTrace();
Alert saveAsPdfAlert = new Alert(AlertType.ERROR);
saveAsPdfAlert.setTitle("ERROR: Error converting to pdf.");
saveAsPdfAlert.setHeaderText("Exception message is:");
saveAsPdfAlert.setContentText(e.getMessage());
saveAsPdfAlert.showAndWait();
}
VBS:
Option Explicit
Dim objExcel, strExcelPath, objSheet
strExcelPath = "XL_FILE"
Set objExcel = CreateObject("Excel.Application")
objExcel.WorkBooks.Open strExcelPath
Set objSheet = objExcel.ActiveWorkbook.Worksheets(1)
objSheet.ExportAsFixedFormat 0, "PDF_FILE",0, 1, 0, , , 0
objExcel.ActiveWorkbook.Close
objExcel.Application.Quit

An alternative is to use a VB script and call it from Java.
Example:
xl2pdf.vbs
Option Explicit
Dim objExcel, strExcelPath, objSheet
strExcelPath = "$XL_FILE"
Set objExcel = CreateObject("Excel.Application")
objExcel.WorkBooks.Open strExcelPath
Set objSheet = objExcel.ActiveWorkbook.Worksheets(1)
objSheet.ExportAsFixedFormat 0, "$PDF_FILE",0, 1, 0, , , 0
objExcel.ActiveWorkbook.Close
objExcel.Application.Quit
In Java (actually kotlin, but easy to translate)
fun xl2pdf(xlFile: Path, pdfFile: Path, timeout: Long = 1, timeUnit: TimeUnit = TimeUnit.MINUTES) {
val tempScript = Files.createTempFile("script", ".vbs")
val script = Files.readAllLines(Paths.get("xl2pdf.vbs"))
.map { it.replace("\$XL_FILE", "$xlFile") }
.map { it.replace("\$PDF_FILE", "$pdfFile") }
Files.write(tempScript, script)
try {
val pb = ProcessBuilder("wscript", tempScript.toString())
val process = pb.start()
val success = process.waitFor(timeout, timeUnit)
if (!success) LOG.error("Could not print PDF within $timeout $timeUnit")
} catch (e: IOException) {
LOG.error("Error while printing Excel file to PDF", e)
}
}

<repository>
<id>com.e-iceblue</id>
<name>e-iceblue</name>
<url>http://repo.e-iceblue.com/nexus/content/groups/public/</url>
</repository>
<dependency>
<groupId>e-iceblue</groupId>
<artifactId>spire.xls.free</artifactId>
<version>5.1.0</version>
</dependency>
import com.spire.xls.FileFormat;
import com.spire.xls.Workbook;
import java.io.File;
public class EIceblueConverter {
public static void main(String[] args) {
for (Sources xls : Sources.values()) {
if (isFileExists(xls)) convert(xls);
}
}
private static boolean isFileExists(Sources xls) {
File file = new File(xls.getPath());
return file.exists() && file.isFile();
}
private static void convert(Sources xls) {
Workbook workbook = new Workbook();
workbook.loadFromFile(xls.getPath());
workbook.getConverterSetting().setSheetFitToPage(true);
workbook.saveToFile(Util.getOutputPath(xls.getPath()), FileFormat.PDF);
}
}
Before converting you should edit view area in file.xls*
... and more convertors, including the interesting solution: use libre office as converter .xls* to .pdf.
(do test it in src/main/java/jodconverter/AppStarter.java)
https://github.com/fedor83/xlsToPdfConverter.git

Here is the full fledge working example
Dependencies :
compile 'com.itextpdf:itextpdf:5.5.13.2'
compile 'org.apache.poi:poi-ooxml:5.0.0'
Java code:
import java.io.*;
import org.apache.poi.ss.usermodel.*;
import java.util.Iterator;
import com.itextpdf.text.*;
import com.itextpdf.text.pdf.*;
public class Excel2PDF {
public static void main(String[] args) throws Exception {
Workbook my_xls_workbook = WorkbookFactory.create(new File("/Users/harshad/Desktop/excel.xlsx"));
Sheet my_worksheet = my_xls_workbook.getSheetAt(0);
short availableColumns = my_worksheet.getRow(0).getLastCellNum();
System.out.println("Available columns : " + availableColumns);
Iterator<Row> rowIterator = my_worksheet.iterator();
Document iText_xls_2_pdf = new Document();
PdfWriter.getInstance(iText_xls_2_pdf, new FileOutputStream("/Users/harshad/Desktop/excel.pdf"));
iText_xls_2_pdf.open();
PdfPTable my_table = new PdfPTable(availableColumns);
PdfPCell table_cell = null;
while (rowIterator.hasNext()) {
Row row = rowIterator.next();
Iterator<Cell> cellIterator = row.cellIterator();
while (cellIterator.hasNext()) {
Cell cell = cellIterator.next();
switch (cell.getCellType()) {
default:
try {
table_cell = new PdfPCell(new Phrase(cell.getStringCellValue()));
} catch (IllegalStateException illegalStateException) {
//TODO: Need to handle exceptions for different type too
if (illegalStateException.getMessage().equals("Cannot get a STRING value from a NUMERIC cell")) {
table_cell = new PdfPCell(new Phrase(String.valueOf(cell.getNumericCellValue())));
}
}
my_table.addCell(table_cell);
break;
}
}
}
iText_xls_2_pdf.add(my_table);
iText_xls_2_pdf.close();
my_xls_workbook.close();
}
}

How to format the values which comes from excel using java

I have a excel file with some values like :
**Status Code** **Method Name**
400 createRequest
401 testRequest
402 mdm
403 fileUpload
and the following code to read and print the data[Late on i will put them in HashMap]
package com.poc.excelfun;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Iterator;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
public class ReadExcelData {
public static void main(String[] args) {
try {
FileInputStream file = new FileInputStream(new File("attachment_status.xls"));
//Get the workbook instance for XLS file
HSSFWorkbook workbook = new HSSFWorkbook(file);
//Get first sheet from the workbook
HSSFSheet sheet = workbook.getSheetAt(0);
//Iterate through each rows from first sheet
Iterator<Row> rowIterator = sheet.iterator();
while(rowIterator.hasNext()) {
Row row = rowIterator.next();
//For each row, iterate through each columns
Iterator<Cell> cellIterator = row.cellIterator();
while(cellIterator.hasNext()) {
Cell cell = cellIterator.next();
switch(cell.getCellType()) {
case Cell.CELL_TYPE_BOOLEAN:
System.out.print(cell.getBooleanCellValue() + "\t\t");
break;
case Cell.CELL_TYPE_NUMERIC:
System.out.print(cell.getNumericCellValue() + "\t\t");
break;
case Cell.CELL_TYPE_STRING:
System.out.print(cell.getStringCellValue() + "\t\t");
break;
}
}
System.out.println("");
}
file.close();
/*
* The following code to create a new work book with the value fetched from the given work book
* FileOutputStream out =
new FileOutputStream(new File("attachment_status_new.xls"));
workbook.write(out);
out.close();*/
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
but the above code returns the following :
Status Code Method Name
400.0 createRequest
401.0 testRequest
402.0 mdm
403.0 fileUpload
If wee the out put the status code comes with .0 but i want to get only 400 not with .0
How to do this.
I have used poi for excel manipulations.
Best Regards
Anto

cell.getNumericCellValue() returns double vaule cast it into int the decimal point will be ignored.

Excel stores almost all numbers in the file format as floating point values, which is why POI will give you back a double for a numeric cell as that's what was really there.
While you could just cast that to an int, that'd just be specific to the one case, and not general. What I think you probably want (though it's not quite clear from your question) is to get a String in Java that contains the number as it would look in Excel? So your cell containing 400.0 and a format rule of integer would come back as the string "400".
If so, you want to do exactly the same thing as in my answer here. To quote:
What you want to do is use the DataFormatter class. You pass this a cell, and it does its best to return you a string containing what Excel would show you for that cell. If you pass it a string cell, you'll get the string back. If you pass it a numeric cell with formatting rules applied, it will format the number based on them and give you the string back.
For your case, I'd assume that the numeric cells have an integer formatting rule applied to them. If you ask DataFormatter to format those cells, it'll give you back a string with the integer string in it.

Convert .csv to .xls in Java

Does anyone here know of any quick, clean way to convert csv files to xls or xlsx files in java?
I have something to manage csv files already in place and I need the extra compatibility for other programs.
Sample code in addition to package names is always well appreciated.
Many thanks,
Justian
Here's my code thus far. I need to remove the returns ("\n") from the lines. Some of my cells contain multiple lines of information (a list), so I can use "\n" in csv to indicate multiple lines within a cell, but xls treats these as if I mean to put them on a new line.
The code is modified from the internet and a little messy at the moment. You might notice some deprecated methods, as it was written in 2004, and be sure to ignore the terrible return statements. I'm just using S.o.p at the moment for testing and I'll clean that up later.
package jab.jm.io;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
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;
public class FileConverter {
public static String ConvertCSVToXLS(String file) throws IOException {
if (file.indexOf(".csv") < 0)
return "Error converting file: .csv file not given.";
String name = FileManager.getFileNameFromPath(file, false);
ArrayList<ArrayList<String>> arList = new ArrayList<ArrayList<String>>();
ArrayList<String> al = null;
String thisLine;
DataInputStream myInput = new DataInputStream(new FileInputStream(file));
while ((thisLine = myInput.readLine()) != null) {
al = new ArrayList<String>();
String strar[] = thisLine.split(",");
for (int j = 0; j < strar.length; j++) {
// My Attempt (BELOW)
String edit = strar[j].replace('\n', ' ');
al.add(edit);
}
arList.add(al);
System.out.println();
}
try {
HSSFWorkbook hwb = new HSSFWorkbook();
HSSFSheet sheet = hwb.createSheet("new sheet");
for (int k = 0; k < arList.size(); k++) {
ArrayList<String> ardata = (ArrayList<String>) arList.get(k);
HSSFRow row = sheet.createRow((short) 0 + k);
for (int p = 0; p < ardata.size(); p++) {
System.out.print(ardata.get(p));
HSSFCell cell = row.createCell((short) p);
cell.setCellValue(ardata.get(p).toString());
}
}
FileOutputStream fileOut = new FileOutputStream(
FileManager.getCleanPath() + "/converted files/" + name
+ ".xls");
hwb.write(fileOut);
fileOut.close();
System.out.println(name + ".xls has been generated");
} catch (Exception ex) {
}
return "";
}
}

Don't know if you know this already, but:
Excel (if that's your real target) is easily able to read .csv files directly, so any conversion you'd do would only be a courtesy to your less "gifted" users.
CSV is a lowest-common-denominator format. It's unlikely for any converter to add information to that found in a .csv file that will make it more useful. In other words, CSV is a "dumb" format and converting it to .xls will (probably) increase file size but not make the format any smarter.
Curtis' suggestion of POI is the first thing that would come to my mind too.
If you're doing this conversion on a Windows machine, another alternative could be Jacob, a Java-COM bridge that would allow you to effectively remote control Excel from a Java program so as to do things like open a file and save in a different format, perhaps even applying some formatting changes or such.
Finally, I've also had some success doing SQL INSERTs (via JDBC) into an Excel worksheet accessed via the JDBC-ODBC bridge. i.e. ODBC can make an Excel file look like a database. It's not very flexible though, you can't ask the DB to create arbitrarily named .XLS files.
EDIT:
It looks to me like readLine() is already not giving you whole lines. How is it to know that carriage return is not a line terminator? You should be able to verify this with debug print statements right after the readLine().
If this is indeed so, it would suck because the way forward would be for you to
either recognize incomplete lines and paste them together after the fact,
or write your own substitute for readLine(). A simple approach would be to read character by character, replacing CRs within a CSV string and accumulating text in a StringBuilder until you feel you have a complete line.
Both alternatives are work you probably weren't looking forward to.

If you want to read or write XLS or XLSX files in Java, Apache POI is a good bet: http://poi.apache.org/

Copy paste the below program,I ran the program and it is working fine,Let me know if you have any concerns on this program.(You need Apache POI Jar to run this program)
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
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.ss.usermodel.Cell;
public class CSVToExcelConverter {
public static void main(String args[]) throws IOException
{
ArrayList arList=null;
ArrayList al=null;
String fName = "test.csv";
String thisLine;
int count=0;
FileInputStream fis = new FileInputStream(fName);
DataInputStream myInput = new DataInputStream(fis);
int i=0;
arList = new ArrayList();
while ((thisLine = myInput.readLine()) != null)
{
al = new ArrayList();
String strar[] = thisLine.split(",");
for(int j=0;j<strar.length;j++)
{
al.add(strar[j]);
}
arList.add(al);
System.out.println();
i++;
}
try
{
HSSFWorkbook hwb = new HSSFWorkbook();
HSSFSheet sheet = hwb.createSheet("new sheet");
for(int k=0;k<arList.size();k++)
{
ArrayList ardata = (ArrayList)arList.get(k);
HSSFRow row = sheet.createRow((short) 0+k);
for(int p=0;p<ardata.size();p++)
{
HSSFCell cell = row.createCell((short) p);
String data = ardata.get(p).toString();
if(data.startsWith("=")){
cell.setCellType(Cell.CELL_TYPE_STRING);
data=data.replaceAll("\"", "");
data=data.replaceAll("=", "");
cell.setCellValue(data);
}else if(data.startsWith("\"")){
data=data.replaceAll("\"", "");
cell.setCellType(Cell.CELL_TYPE_STRING);
cell.setCellValue(data);
}else{
data=data.replaceAll("\"", "");
cell.setCellType(Cell.CELL_TYPE_NUMERIC);
cell.setCellValue(data);
}
//*/
// cell.setCellValue(ardata.get(p).toString());
}
System.out.println();
}
FileOutputStream fileOut = new FileOutputStream("test.xls");
hwb.write(fileOut);
fileOut.close();
System.out.println("Your excel file has been generated");
} catch ( Exception ex ) {
ex.printStackTrace();
} //main method ends
}
}

The tools in Excel are not adequate for what the OP wants to do. He's on the right track there. Excel cannot import multiple CSV files into different worksheets in the same file, which is why you'd want to do it in code. My suggestion is to use OpenCSV to read the CSV, as it can automatically correct for newlines in data and missing columns, and it's free and open source. It's actually very, very robust and can handle all sorts of different non-standard CSV files.

You wrote:
I have something to manage csv files
already in place and I need the extra
compatibility for other programs.
What are those other programs? Are they required to access your data through Excel files, or could they work with an JDBC or ODBC connection to a database? Using a database as the central location, you could extract the data into CSV files or other formats as needed.

I created a small software called csv2xls. It needs Java.

Creating and Editing Excel Documents (.csv) with Java

For this project I'm working on, I want to take multiple excel sheets and then merge them into one, manipulating the data as I please to make everything a little more readable.
What would be the best way to open files, read their contents, store that content, create a new file (.csv), then paste the information in the organization of my choosing?
I definitely need to stick to java, as this will be part of a pre-existing automated process and I don't want to have to change everything to another language.
Is there a useful package out there that I should know about?
Many thanks
Justian

I think any serious work in Excel should consider Joel's solution of letting Office do it for you on a Windows machine you call remotely if necessary. If, however, your needs are simple enough or you really need a pure Java solution, Apache's POI library does a good enough job.

As far as I know, csv is not excel-specific, but rather just a "comma-separated values"-file.
So this might help you.

Writing CSV files is usually very simple, for obvious reasons. You can write your own helper class to do it. The caveat is to ensure that you do not have your delimeter in any of the outputs.
Reading CSV is trickier. There isn't a standard library like there is in Python (a much better language, IMHO, for doing CSV processing), but if you search for it there are a lot of decent free implementations around.
The biggest question is the internal representation in your program: Depending on the size of your inputs and outputs, keeping everything in memory may be out of the question. Can you do everything in one pass? (I mean, read some, write some, etc.)
You may also want to use sparse representations rather than just represent all the spreadsheets in an array.

Maybe you should try this one:
Jxcell,it is a java spreadsheet component,and can read/write/edit all xls/xlsx/csv files.

Try this code
import java.util.*;
import java.util.Map.Entry;
import java.util.concurrent.TimeoutException;
import java.util.logging.Logger;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbookFactory;
public class App {
public void convertExcelToCSV(Sheet sheet, String sheetName) {
StringBuffer data = new StringBuffer();
try {
FileOutputStream fos = new FileOutputStream("C:\\Users\\" + sheetName + ".csv");
Cell cell;
Row row;
Iterator<Row> rowIterator = sheet.iterator();
while (rowIterator.hasNext()) {
row = rowIterator.next();
Iterator<Cell> cellIterator = row.cellIterator();
while (cellIterator.hasNext()) {
cell = cellIterator.next();
CellType type = cell.getCellTypeEnum();
if (type == CellType.BOOLEAN) {
data.append(cell.getBooleanCellValue() + ",");
} else if (type == CellType.NUMERIC) {
data.append(cell.getNumericCellValue() + ",");
} else if (type == CellType.STRING) {
data.append(cell.getStringCellValue() + ",");
} else if (type == CellType.BLANK) {
data.append("" + ",");
} else {
data.append(cell + ",");
}
}
data.append('\n');
}
fos.write(data.toString().getBytes());
fos.close();
}
catch (FileNotFoundException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
}
public static void main(String [] args)
{
App app = new App();
String path = "C:\\Users\\myFile.xlsx";
InputStream inp = null;
try {
inp = new FileInputStream(path);
Workbook wb = WorkbookFactory.create(inp);
for(int i=0;i<wb.getNumberOfSheets();i++) {
System.out.println(wb.getSheetAt(i).getSheetName());
app.convertExcelToCSV(wb.getSheetAt(i),wb.getSheetAt(i).getSheetName());
}
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
finally {
try {
inp.close();
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
}
}
}