MD5 加密

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package com.bra.common.utils;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;public class MD5Util {    /**     * 默认的密码字符串组合，用来将字节转换成 16 进制表示的字符,apache校验下载的文件的正确性用的就是默认的这个组合     */    protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6',            '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };    protected static MessageDigest messagedigest = null;    static {        try {            messagedigest = MessageDigest.getInstance("MD5");        } catch (NoSuchAlgorithmException nsaex) {            System.err.println(MD5Util.class.getName()                    + "初始化失败，MessageDigest不支持MD5Util。");            nsaex.printStackTrace();        }    }    /**     * 生成字符串的md5校验值     *     * @param s     * @return     */    public static String getMD5String(String s) {        return getMD5String(s.getBytes());    }    /**     * 生成文件的md5校验值     *     * @param file     * @return     * @throws IOException     */    public static String getMD5String(File file) throws IOException {        if (!file.exists())            return "";        InputStream fis = new FileInputStream(file);        String result = getMD5String(fis);        fis.close();        return result;    }    /**     * 生成流的md5校验码     *     * @param in     * @return     * @throws IOException     */    public static String getMD5String(InputStream in) throws IOException {        byte[] buffer = new byte[0x10000];        int numRead = 0;        while ((numRead = in.read(buffer)) > 0) {            messagedigest.update(buffer, 0, numRead);        }        return bufferToHex(messagedigest.digest());    }    /**     * 生成字节的md5校验码     *     * @param bytes     * @return     */    public static String getMD5String(byte[] bytes) {        messagedigest.update(bytes);        return bufferToHex(messagedigest.digest());    }    private static String bufferToHex(byte bytes[]) {        return bufferToHex(bytes, 0, bytes.length);    }    private static String bufferToHex(byte bytes[], int m, int n) {        StringBuffer stringbuffer = new StringBuffer(2 * n);        int k = m + n;        for (int l = m; l < k; l++) {            appendHexPair(bytes[l], stringbuffer);        }        return stringbuffer.toString();    }    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {        char c0 = hexDigits[(bt & 0xf0) >> 4];// 取字节中高 4 位的数字转换, >>>        // 为逻辑右移，将符号位一起右移,此处未发现两种符号有何不同        char c1 = hexDigits[bt & 0xf];// 取字节中低 4 位的数字转换        stringbuffer.append(c0);        stringbuffer.append(c1);    }    public static void main(String[] args) {        System.out.println("md52----" + getMD5String("f00156"));    }}
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