Improving Performance of Unique Order Number Generation in Java

The original implementation creates a new SimpleDateFormat object on each call to createUniqueOrderNo(), which wastes memory and CPU time. The method also concatenates a timestamp with a random four‑digit code generated by getRandomLengthCode(int length).

/**
 * 生产唯一的交易订单号
 */
public static String createUniqueOrderNo() {
    SimpleDateFormat nyrsfm = new SimpleDateFormat("yyyyMMddHHmmss");
    return nyrsfm.format(new Date()) + getRandomLengthCode(4);
}

/**
 * 获取随机的短信验证码
 */
public static String getRandomLengthCode(int length) {
    return String.valueOf((int) ((Math.random() * 9 + 1) * Math.pow(10, length - 1)));
}

To improve performance, the SimpleDateFormat instance is made static, eliminating repeated object creation:

static SimpleDateFormat nyrsfm = new SimpleDateFormat("yyyyMMddHHmmss");

/**
 * 生产唯一的交易订单号
 */
public static String createUniqueOrderNo() {
    return nyrsfm.format(new Date()) + getRandomLengthCode(4);
}

A benchmark loop calls createUniqueOrderNo() 10,000 times and measures execution time. The optimized version shows a noticeable speed increase, as illustrated by the provided test result images.

The article also explores the random code generation method. Using string concatenation with the + operator creates additional objects, so String.valueOf() is preferred. A benchmark comparing the two approaches shows only a minor difference, indicating limited further optimization potential.

public static void main(String[] args) {
    List<String> list = new ArrayList<>();
    long nanoMark = getNanoMark();
    range(100000).forEach(x -> {
        // String ss = String.valueOf(1211);
        String ss = 1121 + ""; // alternative concatenation
    });
    output(getFormatNumber(getNanoMark() - nanoMark));
}

Overall, moving the date formatter to a static field significantly improves performance, while the random code generation method offers only marginal gains.