At the first step you sould connect to ldap  with SSL to modify password  of agents then you should unicode your password string with UTF-16LE
I put a sample for you :

        String quotedPassword = '\"' + agent.getPassword() + '\"';
        byte[] unicodePassword;
        DirContext sctx = null;

        try {
            unicodePassword = quotedPassword.getBytes("UTF-16LE");
        } catch (UnsupportedEncodingException uee) {
            throw new LdapAccessException("Cannot encode password" + "???? ???? ???? ??? ????? ???????", uee);
        }

        ModificationItem[] mods = new ModificationItem[2];

        mods[0] = new ModificationItem(DirContext.REPLACE_ATTRIBUTE, new BasicAttribute("unicodePwd", unicodePassword));

            mods[1] = new ModificationItem(DirContext.REPLACE_ATTRIBUTE, new BasicAttribute("userAccountControl", Integer.toString(Agent.UF_NORMAL_ACCOUNT + Agent.UF_DONT_EXPIRE_PASSWD)));

        modifySecurely(agent, mods);