Java 计算文件的MD5值和Hash值

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.StandardOpenOption;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class FileMd5HashUtils {
    private static final char[] hexCode = "0123456789abcdef".toCharArray();


    /**
     * 计算文件的MD5
     * @param fileName 文件的绝对路径
     * @return
     */
    public static String getFileMD5(String fileName) {
        File file = new File(fileName);
        try (InputStream stream = Files.newInputStream(file.toPath(), StandardOpenOption.READ)) {
            MessageDigest digest = MessageDigest.getInstance("MD5");
            byte[] buf = new byte[8192];
            int len;
            while ((len = stream.read(buf)) > 0) {
                digest.update(buf, 0, len);
            }
            return toHexString(digest.digest());
        } catch (IOException e) {
            e.printStackTrace();
            return "";
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
            return "";
        }
    }

    public static String toHexString(byte[] data) {
        StringBuilder r = new StringBuilder(data.length * 2);
        for (byte b : data) {
            r.append(hexCode[(b >> 4) & 0xF]);
            r.append(hexCode[(b & 0xF)]);
        }
        return r.toString();
    }

    /**
     * 计算文件的Hash256值
     * @param fileName 文件的绝对路径
     * @return
     */

    public static String getFileHash256(String fileName){
        File file = new File(fileName);
        FileInputStream fis = null;
        String sha256 = "";
        try {
            fis = new FileInputStream(file);
            MessageDigest md = MessageDigest.getInstance("SHA-256");
            byte buffer[] = new byte[1024];
            int length = -1;
            while ((length = fis.read(buffer, 0, 1024)) != -1) {
                md.update(buffer, 0, length);
            }
            byte[] digest = md.digest();
            sha256 = byte2hexLower(digest);
        } catch (Exception e) {
            e.printStackTrace();
            return "";
        } finally {
            try {
                if (fis != null) {
                    fis.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
                return "";
            }
        }
        return sha256;
    }

    private static String byte2hexLower(byte[] b) {
        String hs = "";
        String stmp = "";
        for (int i = 0; i < b.length; i++) {
            stmp = Integer.toHexString(b[i] & 0XFF);
            if (stmp.length() == 1) {
                hs = hs + "0" + stmp;
            } else {
                hs = hs + stmp;
            }
        }
        return hs;
    }

}