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apache poi copy from very large xls to new workbook sheet

I have very large xls file , which contains two sheets. I want to combine these two sheets into one and copy to new workbook . But I get out of memory exception when I try to access this large xls as below :
FileInputStream fis = new FileInputStream(new File("input.xls"));
HSSFWorkbook workbook = new HSSFWorkbook(fis);
I tried using event api for xls : http://poi.apache.org/spreadsheet/how-to.html#event_api
But using that we can only read the cell values . But here I need to copy to new excel sheet.

Apache POI provides a low-memory footprint SXSSF API to write data to xlsx. It does not load everything in memory at once so it's the solution while working with very large excel files. You may want to consider this.

Unable to read excel files in java getting 2 below error in java

I am trying to read xls and xlsx files with below code and get data from it but i am able to read 70% of xl files i am having but for some i am getting below errors
for remaining files some are giving 1st error and some are giving 2nd error
1)java.lang.IllegalArgumentException: The supplied POIFSFileSystem does not contain a BIFF8 'Workbook' entry. Is it really an excel file?
2)java.lang.IllegalArgumentException: Your InputStream was neither an OLE2 stream, nor an OOXML stream
Both above errors are coming for xlsx extension files
Why am i able to read some and not some files and is there any global solution to this
My java code:
FileInputStream input = new FileInputStream("/Users/Xl_Files/"+fileName);
Workbook wb = WorkbookFactory.create(input);
Sheet sheet = wb.getSheetAt(0);
String var = String.valueOf(sheet.getRow(Row).getCell(Colon));

.getAllPictures() Method doesn't get all the pictures in .xlsx excel file

I can't get all the pictures in .xlsx file that I made in MS Excel while when I used Google spreadsheet to create a .xlsx file it can read all the pictures that I inserted there.
My code is here:
XSSFWorkbook workbook = new XSSFWorkbook("Sample.xlsx");
XSSFSheet sheet = workbook.getSheetAt(0);
List lst = workbook.getAllPictures();
Is there a way on how to read ALL the images in a .xlsx file which is done by MS Excel?

error while inputing an csv file into java code

the question is how can i use java to input a csv file and output an xls file
is there any specefic api or lib which can help question gonna help so why it s error on opening a sheet
FileOutputStream fos = new FileOutputStream(outputFile);
HSSFWorkbook workbook = new HSSFWorkbook(new FileInputStream(inputFile));
workbook.setMissingCellPolicy(Row.CREATE_NULL_AS_BLANK);
HSSFSheet sheet = workbook.getSheetAt(0);
after i tried i think it s due to a memor problem idk

When trying to open the .xlsx file created by selenium, getting a message stating that the file is corrupted

I created an .xlsx file using selenium through File "fil.createNewFile()", the file got created in the location but when i try to open the file i am getting a message "Excel cannot open the file 'Example.xlsx' because the file format or file extension is not valid....". Why is this happening. Please guide me to over come this problem.
Thanks in advance...

What eltabo mentioned is correct. Below is a code sample from Apache POI which will create a blank excel file.
HSSFWorkbook workbook = new HSSFWorkbook();
FileOutputStream out = new FileOutputStream(new File("C:\\new.xls"));
workbook.write(out);
out.close();

I guess you are trying something like:
File fil = new File("Example.xlsx");
fil.createNewFile();
Well, it this is your case you're creating a file with xlsx extension, but it's not truly a Excel file (it's empty). If you try to create a new file using Excel or File Explorer, you can see that a new fresh xlsx file weight about 10kb. If you need to create a Excel file you need to use Apache POI, or another library.
You need to add a sheet at least:
XSSFWorkbook wb = new XSSFWorkbook();
Sheet sheet = wb.createSheet();
FileOutputStream fileOut = new FileOutputStream("Example.xlsx");
wb.write(fileOut);
fileOut.close();
PS: I use poi-ooxml, since you use a xlsx file.
Hope it helps.