How to combine two excel files using java -

i having 3 xls file. need create new file combining 3 files.

the files follows:

• file 1 has 2 sheets
• file 2 has 1 sheet
• file 3 has 1 sheet

the goal have sheets of 3 files in 1 single file.

here have tried:

// converting csv excel: dateformat dateformat = new simpledateformat("mmddyyyy-hhmmss"); date date = new date(); string date1 = dateformat.format(date);  workbook wb = new hssfworkbook(); creationhelper helper = wb.getcreationhelper(); sheet sheet = wb.createsheet("ebs_input_file"); string path = "path.csv"; csvreader reader = new csvreader(new filereader(path)); string[] line; string web; set<string> data = new hashset<string>();  int r = 0; stringtokenizer st = null; string strline = ""; int token = 0; string address = null; while ((line = reader.readnext()) != null) {     row row = sheet.createrow((short) r);     (int = 0; < line.length; i++)         row.createcell(i).setcellvalue(helper.createrichtextstring(line[i]));     st = new stringtokenizer(strline, ",");     while (st.hasmoretokens())     {         token++;         string token1 = st.nexttoken();     }     r++;      fileoutputstream fileout = new fileoutputstream("excel.xls");     wb.write(fileout);     fileout.close();  } system.out.println("file converted successful!");  // excel file 1 workbook sourcebook1 = new hssfworkbook(         new fileinputstream("excel2.xls")); // excel file 2 workbook sourcebook2 = new hssfworkbook(         new fileinputstream("excel.xls")); // combining excel file 1 & 2 sourcebook1.combine(sourcebook2); // saving in excel file 3 sourcebook1.save("excel3.xls");       ` 

also tried:

 string [] excelsheets = {"excel.xls","excel2.xls"};  //root folder excel files read  final string root_folder = "path";  //output file name merged excel file (consolidated file)  final string output_file = path+"excel3.xls";   workbook [] workbook = new workbook[excelsheets.length];   for(int = 0; < excelsheets.length; i++) {      workbook[i] = new hssfworkbook(new fileinputstream(root_folder +   excelsheets[i]));  }   workbook newworkbook = new hssfworkbook();   for(int = 0; < excelsheets.length; i++) {      newworkbook = copyexcelsheets.copy(workbook[i], newworkbook, "book-" + i);  }          //write on new file  fileoutputstream fileout1;  fileout1 = new fileoutputstream(output_file);              newworkbook.write(fileout1);   for(int = 0; < excelsheets.length; i++) {      workbook[i].close();  }           newworkbook.close();  fileout1.close();  } 

but can't achieve desired result. doing wrong?