I want to validate if all the files in a directory are of a certain type. What I did so far is.

```
private static final String[] IMAGE_EXTS = { "jpg", "jpeg" };

private void validateFolderPath(String folderPath, final String[] ext) {

        File dir = new File(folderPath);

        int totalFiles = dir.listFiles().length;

        // Filter the files with JPEG or JPG extensions.
        File[] matchingFiles = dir.listFiles(new FileFilter() {
            public boolean accept(File pathname) {
                return pathname.getName().endsWith(ext[0])
                        || pathname.getName().endsWith(ext[1]);
            }
        });

        // Check if all the files have JPEG or JPG extensions
        // Terminate if validation fails.
        if (matchingFiles.length != totalFiles) {
            System.out.println("All the tiles should be of type " + ext[0]
                    + " or " + ext[1]);
            System.exit(0);
        } else {
            return;
        }

    }

```

This works fine if the file name have an extension like {file.jpeg, file.jpg}
This fails if the files have no extensions {file1 file2}. 
When I do the following in my terminal I get: 

```
$ file folder/file1 
folder/file1: JPEG image data, JFIF standard 1.01

```

**Update 1:**

I tried to get the magic numbers of the file to check if it is JPEG:

```
for (int i = 0; i < totalFiles; i++) {
            DataInputStream input = new DataInputStream(
                    new BufferedInputStream(new FileInputStream(
                            dir.listFiles()[i])));

            if (input.readInt() == 0xffd8ffe0) {
                isJPEGFlag = true;
            } else {
                isJPEGFlag = false;
                try {
                    input.close();
                } catch (IOException ignore) {
                }
                System.out.println("File not JPEG");
                System.exit(0);
            }
        }

```

I ran into another problem. There are some **.DS\_Store** files in my folder. 
Any idea how to ignore them ?