Uncompilable source code: you define variable out inside try-catch scope and then you use it inside another try-catch.
Try this code:
try {
FileOutputStream out = new FileOutputStream("C:\\Documents and Settings\\INGENIERIA2\\Mis documentos\\Informe.xls");
exceldoc.write(out);
out.close();
} catch (FileNotFoundException ex) {
Logger.getLogger(PruebaExcel.class.getName()).log(Level.SEVERE, null, ex);
}