public class PasswordHelper {    private RandomNumberGenerator randomNumberGenerator =     new SecureRandomNumberGenerator();    private String algorithmName = "md5";    private final int hashIterations = 2;    public void encryptPassword(User user) {        user.setSalt(randomNumberGenerator.nextBytes().toHex());        String newPassword = new SimpleHash(                algorithmName,                user.getPassword(),                ByteSource.Util.bytes(user.getCredentialsSalt()),                hashIterations).toHex();        user.setPassword(newPassword);    }} 

　　在创建账户及修改密码时直接把生成密码操作委托给PasswordHelper。