package com.doumee.core.utils;
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import java.security.SecureRandom;
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import java.util.HashSet;
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import java.util.Random;
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import java.util.Set;
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import java.util.concurrent.ThreadLocalRandom;
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import java.util.List;
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import java.util.ArrayList;
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/**
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* 不重复核销码生成器
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* 用于生成唯一且易于识别的核销码
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*/
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public class UniqueVerificationCodeGenerator {
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private final Set<String> usedCodes;
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private final int codeLength;
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private final String prefix;
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private final String suffix;
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private final Random random;
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private final boolean useSecureRandom;
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private final CodeFormat format;
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// 核销码格式枚举
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public enum CodeFormat {
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NUMERIC_ONLY("0123456789"),
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ALPHANUMERIC("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"),
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LETTERS_ONLY("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
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private final String characters;
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CodeFormat(String characters) {
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this.characters = characters;
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}
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public String getCharacters() {
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return characters;
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}
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}
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/**
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* 构造函数 - 默认数字格式
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* @param codeLength 核销码长度
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*/
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public UniqueVerificationCodeGenerator(int codeLength) {
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this(codeLength, "", "", CodeFormat.NUMERIC_ONLY, false);
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}
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/**
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* 构造函数 - 完整配置
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* @param codeLength 核销码长度
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* @param prefix 前缀
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* @param suffix 后缀
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* @param format 核销码格式
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* @param useSecureRandom 是否使用安全随机数生成器
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*/
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public UniqueVerificationCodeGenerator(int codeLength, String prefix, String suffix,
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CodeFormat format, boolean useSecureRandom) {
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if (codeLength < 1) {
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throw new IllegalArgumentException("核销码长度必须大于0");
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}
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this.codeLength = codeLength;
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this.prefix = prefix != null ? prefix : "";
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this.suffix = suffix != null ? suffix : "";
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this.format = format;
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this.usedCodes = new HashSet<>();
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this.useSecureRandom = useSecureRandom;
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this.random = useSecureRandom ? new SecureRandom() : ThreadLocalRandom.current();
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}
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/**
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* 生成下一个不重复的核销码
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* @return 核销码，如果没有可用组合则返回null
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*/
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public String nextUniqueCode() {
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int maxAttempts = 1000;
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int attempts = 0;
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while (attempts < maxAttempts) {
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String code = generateCode();
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if (!usedCodes.contains(code)) {
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usedCodes.add(code);
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return code;
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}
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attempts++;
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}
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// 如果随机生成失败，尝试顺序生成
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return generateSequentialCode();
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}
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/**
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* 生成指定数量的不重复核销码
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* @param count 数量
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* @return 核销码列表
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*/
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public List<String> nextUniqueCodes(int count) {
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List<String> result = new ArrayList<>();
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for (int i = 0; i < count; i++) {
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String code = nextUniqueCode();
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if (code == null) {
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break; // 没有更多可用组合
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}
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result.add(code);
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}
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return result;
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}
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/**
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* 生成单个核销码（不检查重复）
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* @return 核销码
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*/
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private String generateCode() {
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StringBuilder sb = new StringBuilder();
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sb.append(prefix);
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String characters = format.getCharacters();
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for (int i = 0; i < codeLength; i++) {
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int index = random.nextInt(characters.length());
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sb.append(characters.charAt(index));
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}
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sb.append(suffix);
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return sb.toString();
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}
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/**
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* 顺序生成核销码（作为备选方案）
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*/
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private String generateSequentialCode() {
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String characters = format.getCharacters();
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long totalCombinations = (long) Math.pow(characters.length(), codeLength);
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if (usedCodes.size() >= totalCombinations) {
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return null; // 所有可能组合都已使用
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}
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// 寻找下一个未使用的组合
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for (long i = 0; i < totalCombinations; i++) {
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String code = convertToCode(i, characters);
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String fullCode = prefix + code + suffix;
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if (!usedCodes.contains(fullCode)) {
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usedCodes.add(fullCode);
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return fullCode;
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}
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}
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return null;
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}
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/**
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* 将数字转换为指定字符集的编码
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*/
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private String convertToCode(long number, String characters) {
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StringBuilder sb = new StringBuilder();
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long base = characters.length();
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for (int i = 0; i < codeLength; i++) {
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sb.append(characters.charAt((int) (number % base)));
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number /= base;
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}
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return sb.reverse().toString();
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}
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/**
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* 重置生成器
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*/
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public void reset() {
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usedCodes.clear();
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}
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/**
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* 获取已使用的核销码数量
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*/
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public int getUsedCount() {
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return usedCodes.size();
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}
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/**
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* 检查是否还有可用的核销码组合
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*/
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public boolean hasMoreCodes() {
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String characters = format.getCharacters();
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long totalCombinations = (long) Math.pow(characters.length(), codeLength);
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return usedCodes.size() < totalCombinations;
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}
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// ==================== 静态便捷方法 ====================
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/**
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* 生成数字型核销码（默认6位）
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*/
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public static String generateNumericCode() {
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return generateNumericCode(6);
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}
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/**
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* 生成指定长度的数字型核销码
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*/
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public static String generateNumericCode(int length) {
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UniqueVerificationCodeGenerator generator =
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new UniqueVerificationCodeGenerator(length, "", "", CodeFormat.NUMERIC_ONLY, true);
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return generator.nextUniqueCode();
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}
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/**
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* 批量生成数字型核销码
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*/
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public static List<String> generateNumericCodes(int length, int count) {
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UniqueVerificationCodeGenerator generator =
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new UniqueVerificationCodeGenerator(length, "", "", CodeFormat.NUMERIC_ONLY, true);
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return generator.nextUniqueCodes(count);
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}
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/**
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* 生成带前缀的核销码
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*/
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public static String generatePrefixedCode(String prefix, int length) {
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UniqueVerificationCodeGenerator generator =
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new UniqueVerificationCodeGenerator(length, prefix, "", CodeFormat.NUMERIC_ONLY, true);
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return generator.nextUniqueCode();
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}
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/**
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* 生成字母数字混合核销码
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*/
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public static String generateAlphanumericCode(int length) {
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UniqueVerificationCodeGenerator generator =
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new UniqueVerificationCodeGenerator(length, "", "", CodeFormat.ALPHANUMERIC, true);
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return generator.nextUniqueCode();
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}
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/**
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* 生成订单号格式的核销码（如：ORD20241201XXXXXX）
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*/
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public static String generateOrderCode(String prefix) {
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String datePart = java.time.LocalDateTime.now().format(
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java.time.format.DateTimeFormatter.ofPattern("yyyyMMdd"));
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UniqueVerificationCodeGenerator generator =
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new UniqueVerificationCodeGenerator(6, prefix + datePart, "", CodeFormat.NUMERIC_ONLY, true);
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return generator.nextUniqueCode();
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}
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/**
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* 生成优惠券码格式（如：COUPON-XXXXXX）
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*/
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public static String generateCouponCode() {
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UniqueVerificationCodeGenerator generator =
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new UniqueVerificationCodeGenerator(8, "COUPON-", "", CodeFormat.ALPHANUMERIC, true);
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return generator.nextUniqueCode();
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}
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}
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