How to validate file type in java

Question

I have created a text file with some content. I changed its extension to .xlsx. I used this code to validate file-

String filepath = "C:\\Users\\prabhat.sameer\\Desktop\\test.xlsx";
File f = new File(filepath);
String mimetype= new MimetypesFileTypeMap().getContentType(f);
String type = mimetype.split("/")[0];
System.out.println("type " + type);
if (type.equals("text")) {
    System.out.println("It's an text file");
} else {
    System.out.println("It's NOT an text file");
}

Its content type also changed with change of extension. How to validate this?

Answer 1

If you open the file by double-clicking on it, are you able to read the data? Usually a special library like POI is required to write to excel so I would be surprised if it does. If your txt file has data in csv(comma separated) format, then changing the extension to .csv should work for you.