Android 生成MD5文件

今天遇到一個需求就是上傳文件是要爲MD5的文件，爲了減少服務器壓力。

/**
* SD卡文件MD5文件校驗
*
* @param file
* @return
*/
public static String fileMD5(File file) {

    try {
        byte[] hash;
        byte[] buffer = new byte[8192];
        MessageDigest md = MessageDigest.getInstance("MD5");
        FileInputStream fis = new FileInputStream(file);
        int len;
        while ((len = fis.read(buffer)) != -1) {
            md.update(buffer, 0, len);
        }
        hash = md.digest();

        //對生成的16字節數組進行補零操作
        StringBuilder hex = new StringBuilder(hash.length * 2);
        for (byte b : hash) {
            if ((b & 0xFF) < 0x10) {
                hex.append("0");
            }
            hex.append(Integer.toHexString(b & 0xFF));
        }
        return hex.toString();
    } catch (NoSuchAlgorithmException e) {
        throw new RuntimeException("NoSuchAlgorithmException", e);
    } catch (UnsupportedEncodingException e) {
        throw new RuntimeException("UnsupportedEncodingException", e);
    } catch (IOException e) {
        e.printStackTrace();
    }

    return "";

}