[Java] Mime type detection

FileMimeTypeService.java

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Paths;

public class FileMimeTypeService {

	public String getContentType(String file) {
		
		String mimeType = null;
		
		try { mimeType = fileInfoFromOs(file); } catch(Exception e) {}
		
		if(mimeType == null) 
			try { mimeType = fileInfoFromJava(file); } catch(Exception e) {}

		return mimeType;
	}

	protected String fileInfoFromJava(String file) throws Exception {
		return Files.probeContentType(Paths.get(file));
	}

	protected String fileInfoFromOs(String file) throws Exception {
		
    	Process process = Runtime.getRuntime().exec("file -b --mime-type " + file);
    	int returnCode = process.waitFor();
    	
    	if(returnCode != 0)
    		return null;
    	
    	StringBuilder buff = new StringBuilder();
    	
    	try(BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream(), Charset.forName("UTF-8")))) {
	    	
	    	String line = null;
	    	while((line = reader.readLine()) != null) {
	    		buff.append(line);
	    	}
    	}

    	return buff.length() == 0 ? null : buff.toString();
	}

}