Getting a File's MD5 Checksum in Java

java

md5

streams

exceptions

byNikita Barsukov·Aug 7, 2024

Here's a quick and easy method to calculate an MD5 checksum in Java using MessageDigest:

import java.io.*;
import java.security.*;

public class ChecksumHelper {

    public static String getMD5Checksum(String path) throws NoSuchAlgorithmException, IOException {
        MessageDigest md = MessageDigest.getInstance("MD5");
        try (InputStream is = Files.newInputStream(Paths.get(path));
            DigestInputStream dis = new DigestInputStream(is, md)) {
            byte[] buffer = new byte[4096];
            while (dis.read(buffer) != -1) {
                // Keep calm and keep on reading.
            }
        }
        // Turning bytes into beauty.
        return convertToHex(md.digest());
    }

    private static String convertToHex(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        for (byte b : bytes) {
            sb.append(String.format("%02x", b));
        }
        return sb.toString();
    }
}

Call ChecksumHelper.getMD5Checksum with your file path and get your sweet MD5 sum back.

Safety first: dealing with streams and exceptions

Try-with-resources: friend of the streams

Working with any kind of streams? Remember try-with-resources is your pal, ensuring you don't leave streams open and prevent resource leaks. With DigestInputStream, you're reading, computing the checksum, and managing the stream – all in one go!

Handling those I/O exceptions

The method getMD5Checksum produces two exceptions - NoSuchAlgorithmException and IOException that you should catch in your higher-level methods and debug accordingly.

Memory-friendly: working with big ol’ files

Got a massive file on your hands? Consider your RAM and process your file in chunks. This will keep your memory consumption LOW, and prevent out of memory errors.

Exploring the neighbourhood: alternative libraries and methods

Apache Commons Codec: short and sweet

Need a one-liner? Ring the bell for DigestUtils.md5Hex from the Apache Commons Codec:

String md5Checksum = DigestUtils.md5Hex(new FileInputStream("file.txt"));

Google Guava: clean simplicity

Google Guava has a crisp solution as well, with the Files.hash() method:

HashCode md5Checksum = Files.asByteSource(new File("file.txt")).hash(Hashing.md5());

Beyond MD5: stepping into the secure zone

Using your checksum for cryptographic purposes? MD5 may not be your best bet. Check out more secure alternatives like SHA-256, bcrypt, or scrypt.

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Safety first: dealing with streams and exceptions Memory-friendly: working with big ol’ files Exploring the neighbourhood: alternative libraries and methods