转载:6位百万级邀请码生成方法

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废话少说,直接上代码。

import java.util.Arrays;

public class InviteCode {

	/**
	 * 随机字符串
	 */
	private static final char[] CHARS = new char[] { 'F', 'L', 'G', 'W', '5', 'X', 'C', '3', '9', 'Z', 'M', '6', '7',
			'Y', 'R', 'T', '2', 'H', 'S', '8', 'D', 'V', 'E', 'J', '4', 'K', 'Q', 'P', 'U', 'A', 'N', 'B' };

	private final static int CHARS_LENGTH = 32;
	/**
	 * 邀请码长度
	 */
	private final static int CODE_LENGTH = 6;

	/**
	 * 随机数据
	 */
	private final static long SLAT = 1234561L;

	/**
	 * PRIME1 与 CHARS 的长度 L互质,可保证 ( id * PRIME1) % L 在 [0,L)上均匀分布
	 */
	private final static int PRIME1 = 3;

	/**
	 * PRIME2 与 CODE_LENGTH 互质,可保证 ( index * PRIME2) % CODE_LENGTH 在
	 * [0,CODE_LENGTH)上均匀分布
	 */
	private final static int PRIME2 = 11;

	/**
	 * 生成邀请码
	 *
	 * @param id 唯一的id主键
	 * @return code
	 */
	public static String gen(Long id) {
		// 补位
		id = id * PRIME1 + SLAT;
		// 将 id 转换成32进制的值
		long[] b = new long[CODE_LENGTH];
		// 32进制数
		b[0] = id;
		for (int i = 0; i < CODE_LENGTH - 1; i++) {
			b[i + 1] = b[i] / CHARS_LENGTH;
			// 按位扩散
			b[i] = (b[i] + i * b[0]) % CHARS_LENGTH;
		}
		b[5] = (b[0] + b[1] + b[2] + b[3] + b[4]) * PRIME1 % CHARS_LENGTH;

		// 进行混淆
		long[] codeIndexArray = new long[CODE_LENGTH];
		for (int i = 0; i < CODE_LENGTH; i++) {
			codeIndexArray[i] = b[i * PRIME2 % CODE_LENGTH];
		}

		StringBuilder buffer = new StringBuilder();
		Arrays.stream(codeIndexArray).boxed().map(Long::intValue).map(t -> CHARS[t]).forEach(buffer::append);
		return buffer.toString();
	}

	/**
	 * 将邀请码解密成原来的id
	 *
	 * @param code 邀请码
	 * @return id
	 */
	public static Long decode(String code) {
		if (code.length() != CODE_LENGTH) {
			return null;
		}
		// 将字符还原成对应数字
		long[] a = new long[CODE_LENGTH];
		for (int i = 0; i < CODE_LENGTH; i++) {
			char c = code.charAt(i);
			int index = findIndex(c);
			if (index == -1) {
				// 异常字符串
				return null;
			}
			a[i * PRIME2 % CODE_LENGTH] = index;
		}

		long[] b = new long[CODE_LENGTH];
		for (int i = CODE_LENGTH - 2; i >= 0; i--) {
			b[i] = (a[i] - a[0] * i + CHARS_LENGTH * i) % CHARS_LENGTH;
		}

		long res = 0;
		for (int i = CODE_LENGTH - 2; i >= 0; i--) {
			res += b[i];
			res *= (i > 0 ? CHARS_LENGTH : 1);
		}
		return (res - SLAT) / PRIME1;
	}

	/**
	 * 查找对应字符的index
	 *
	 * @param c 字符
	 * @return index
	 */
	private static int findIndex(char c) {
		for (int i = 0; i < CHARS_LENGTH; i++) {
			if (CHARS[i] == c) {
				return i;
			}
		}
		return -1;
	}
}

转载自:https://springboot.io/t/topic/1159