SHA1 对文件求信息摘要的实现

package sup.orange.learn;

import java.io.FileInputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * Created by re-x on 11/4/14.
 */
public class HashFileTest {
    public static void main(String[] args) throws IOException, NoSuchAlgorithmException {
        boolean result = verifyChecksum("/home/re-x/Downloads/linux-1.0.tar.bz2", "4b3de322714d911c8bb46ceda2dbf541e6ab24f4");
        System.out.println("Does the file‘s checksum matches the expected one? " + result);
    }

    /**
     * Verifies file‘s SHA1 checksum.
     * @param file, filepath and namd of a file that is to be verified.
     * @param testChecksum, the expected checksum.
     * @return true if the expeceted SHA1 checksum matches the file‘s SHA1 checksum; false otherwise
     * @throws java.security.NoSuchAlgorithmException
     * @throws java.io.IOException
     */
    public static boolean verifyChecksum(String file, String testChecksum) throws NoSuchAlgorithmException, IOException {
        MessageDigest messageDigest = MessageDigest.getInstance("SHA1");
        FileInputStream fis = new FileInputStream(file);

        byte[] data = new byte[1024];
        int read = 0;
        while ((read = fis.read(data)) != -1) {
            messageDigest.update(data, 0, read);
        }

        byte[] hashBytes = messageDigest.digest();

        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < hashBytes.length; i++) {
            sb.append(Integer.toString((hashBytes[i] & 0xff) + 0x100, 16).substring(1));
        }

        String fileHash = sb.toString();
        System.out.println(file+" sha1 is: "+fileHash);

        return fileHash.equals(testChecksum);
    }
}