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• This answer How can I determine if a file is a PDF file? recommends to download another library, but my requirement is that I just need to check if a file is directory is of type PDF or not




• Using complete library for this use looks like overkill



• Are there any ways to know that a Java File is of type PDF?

Well, according to wikipedia PDF files start with magic numbers: "%PDF" (hex 25 50 44 46) so maybe you should check the InputStream from the file and check that.

Well, kind of a hackish solution would be to look at the full file name and see if it ends in ".pdf". The following should help:

import javax.activation.*;  



public class ShowMimeType  

{  

    public static void main(String args) {  

        FileDataSource ds = new FileDataSource(args[0]);  

        String contentType = ds.getContentType();  

        System.out.println("The MIME type of the file " + args[0] + " is: " + contentType);  

    }  

}  

SimpleMagic is a Java library for resolving content types:

<!-- pom.xml -->

    <dependency>

        <groupId>com.j256.simplemagic</groupId>

        <artifactId>simplemagic</artifactId>

        <version>1.8</version>

    </dependency>

import com.j256.simplemagic.ContentInfo;

import com.j256.simplemagic.ContentInfoUtil;

import com.j256.simplemagic.ContentType;

// ...



public class SimpleMagicSmokeTest {



    private final static Logger log = LoggerFactory.getLogger(SimpleMagicSmokeTest.class);



    @Test

    public void smokeTestSimpleMagic() throws IOException {

        ContentInfoUtil util = new ContentInfoUtil();

        File possiblePdfFile = new File("/path/to/possiblePdfFile.pdf");

        ContentInfo info = util.findMatch(possiblePdfFile);



        log.info( info.toString() );

        assertEquals( ContentType.PDF, info.getContentType() );

    }

If checking the file extension is not satisfactory, you coudl try checking the files magic number by reading a few bytes of the file

PDF files start with "%PDF" (hex 25 50 44 46).

This might sound a little bit too obvious, but check the extension on the filename.

If it's good enough for explorer, it should be good enough for you

Combines lighter URLCOnnection.guessContentTypeFromStream() which returns null for some mimeTypes, with heavier AutoDetectParser.

if(currentImageType ==null){

                ByteArrayInputStream is = new ByteArrayInputStream(image);

                String mimeType = URLConnection.guessContentTypeFromStream(is);

                if(mimeType == null){

                    AutoDetectParser parser = new AutoDetectParser();

                    Detector detector = parser.getDetector();

                    Metadata md = new Metadata();

                    mimeType = detector.detect(is,md).toString();



                    if (mimeType.contains("pdf")){

                        mimeType ="pdf";

                    }

                    else if(mimeType.contains("tif")||mimeType.contains("tiff")){

                        mimeType = "tif";

                    }

                }

                if(mimeType.contains("png")){

                    mimeType ="png";

                }

                else if( mimeType.contains("jpg")||mimeType.contains("jpeg")){

                    mimeType = "jpg";

                }

                else if (mimeType.contains("pdf")){

                    mimeType ="pdf";

                }

                else if(mimeType.contains("tif")||mimeType.contains("tiff")){

                    mimeType = "tif";

                }



                currentImageType = ImageType.fromValue(mimeType);

            }