Retrieves the md5 sum of a file. - Java Security

Java examples for Security:MD5

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Description

Retrieves the md5 sum of a file.

Demo Code


import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Locale;

public class Main{
    public static void main(String[] argv) throws Exception{
        File file = new File("Main.java");
        System.out.println(md5sum(file));
    }/* w  w  w  .j ava 2  s.  c  om*/
    private static final int BUFFER = 8192;
    private static final String MD5 = "MD5";
    /**
     * Retrieves the md5 sum of a file.
     * 
     * @param file - The file to check.
     * @return The md5 sum.
     * @throws IllegalArgumentException If the file is <code>null</code> or is
     *             not a file.
     * @throws IOException If an error occurs while reading the file.
     * @throws NoSuchAlgorithmException If it is impossible to produce a
     *             checksum by using the specified method/algorithm.
     */
    public static String md5sum(final File file)
            throws IllegalArgumentException, IOException,
            NoSuchAlgorithmException {
        return computeCheckSum(file, MD5);
    }
    /**
     * @param file
     * @param algorithm
     * @return
     * @throws IllegalArgumentException If the file is <code>null</code> or is
     *             not a file.
     * @throws IOException If an error occurs while reading the file.
     * @throws NoSuchAlgorithmException If it is impossible to produce a
     *             checksum by using the specified method/algorithm.
     */
    private static String computeCheckSum(final File file,
            final String algorithm) throws IllegalArgumentException,
            IOException, NoSuchAlgorithmException {

        if (file == null)
            throw new IllegalArgumentException(
                    "The file for which to check the sum cannot be null.");
        if (!file.isFile())
            throw new IllegalArgumentException("Must be a file.");

        BufferedInputStream bis = null;
        try {
            final MessageDigest checksum = MessageDigest
                    .getInstance(algorithm);
            bis = new BufferedInputStream(new FileInputStream(file));
            int length;
            final byte[] data = new byte[BUFFER];
            while ((length = bis.read(data, 0, BUFFER)) != -1) {
                checksum.update(data, 0, length);
            }
            bis.close();
            final byte[] bytes = checksum.digest();
            return toHex(bytes).toUpperCase(Locale.ENGLISH);

        } finally {
            CommonUtils.closeStreamQuietly(bis);
        }
    }
    /**
     * Converts an array of byte into an hexadecimal string format.
     * 
     * @param bytes - The byte array to convert
     * @return The string in hexadecimal format
     */
    private static String toHex(final byte[] bytes) {
        final BigInteger bigInt = new BigInteger(1, bytes);
        return bigInt.toString(16);
    }
}

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