MD5和getCRC

原创已于 2023-07-20 17:26:44 修改 · 152 阅读

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#java #开发语言

于 2023-07-20 16:19:15 首次发布

唯一标记文件内容的方式

方式1:

1.1.MD5 (容易生成30位的值)

public static MessageDigest MD5;
static {
    try {
        MD5 = MessageDigest.getInstance("MD5");
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    }
}
public static String mkMd5(byte[] bs) {
    MD5.reset();
    MD5.update(bs);
    return toHex(MD5.digest());
}
public static String toHex(byte[] bs) {
    StringBuilder builder = new StringBuilder();
    for (byte b : bs) {
        builder.append(Integer.toHexString(b & 0xff));
    }
    return builder.toString();
}

//测试

String readMd5 = mkMd5(ByteStreams.toByteArray(objectContent));

1.2. getCRC(是long类型的值)

public long getCrc(InputStream inputStream)
        throws IOException
{
    CRC32 crc32 = new CRC32();
    byte[] data = new byte[1024];

    int i = 0;
    while ((i = inputStream.read(data)) > 0) {
        crc32.update(data, 0, i);
    }
    return crc32.getValue();
}

//测试

long readMd5 = getCrc(objectContent);

方式2

2.1. MD5(只会生成32位的值, 建议采用)

@Test
public void testMD5() throws NoSuchAlgorithmException {
    byte[] content = new byte[100];
    MessageDigest digest = MessageDigest.getInstance("MD5");
    digest.update(content);
    
    byte[] md5Bytes = digest.digest();
    String md5 = BaseEncoding.base16().lowerCase().encode(md5Bytes);
}

2.2.getCRC

@Test
public void testCrc() {
    byte[] content = new byte[100];
    CRC32 crc32 = new CRC32();
    crc32.update(content);
    long crcCode = crc32.getValue();
}