URLHasher - Get MD5/SHA1/other MessageDigest hash of a URL's contents

URLHasher.java

package urlhasher;

import java.io.IOException;
import java.io.InputStream;
import java.math.BigInteger;
import java.net.URL;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class URLHasher {
    
    private URL url;
    private MessageDigest hash;
    
    public URLHasher(URL url) throws AlgorithmNotFoundException {
        this(url, "MD5");
    }
    
    public URLHasher(URL url, String algorithm) throws AlgorithmNotFoundException {
        this.url = url;
        
        try {
            hash = MessageDigest.getInstance(algorithm);
        } catch(NoSuchAlgorithmException nsae) {
            throw new AlgorithmNotFoundException();
        }
    }
    
    private InputStream getStream() throws IOException {
        return url.openStream();
    }
    
    public String getHash() throws IOException {
        InputStream inputStream = getStream();

        int read;
        byte[] dataTmp = new byte[4096];

        while((read = inputStream.read(dataTmp)) != -1)
            hash.update(dataTmp, 0, read);
        
        byte[] hashDigest = hash.digest();
        hash.reset();
        
        return bytesToHex(hashDigest);
    }
    
    public static String bytesToHex(byte[] bytes) {
        BigInteger bigInt = new BigInteger(1, bytes);
        return String.format("%0" + (bytes.length << 1) + "x", bigInt);
    }
    
    class AlgorithmNotFoundException extends NoSuchAlgorithmException {};
    
}