ID生成工具类

package com.util;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Random;

/**
 * ID生成工具类
 * 提供2种ID
 * getID() 生成18位ID，生成ID格式为:yyMMdd+12位大小写字母+数字随机字符串
 * getLongID() 生成26位ID，生成ID格式为:yyyyMMddHHmmss+12位大小写字母+数字随机字符串
 * <p>
 * Created by zyb on 2016/8/18.
 */
public class IDUtil {

    @SuppressWarnings({ "MethodCanBeVariableArityMethod", "Annotation" })
    public static void main(String[] args) {
        //System.out.println(IDUtil.getID());
        //System.out.println(IDUtil.getLongID());
    }

    /**
     * 生成18位ID，生成ID格式为:yyMMdd+12位大小写字母+数字随机字符串
     *
     * @return String
     */
    public synchronized static String getID() {
        return getDate() + getRandomString(IDLENGTH);
    }

    /**
     * 生成26位ID，生成ID格式为:yyyyMMddHHmmss+12位大小写字母+数字随机字符串
     *
     * @return String
     */
    public synchronized static String getLongID() {
        return getDateTime() + getRandomString(IDLENGTH);
    }

    /**
     * 生成随机字符串的长度
     */
    private final static int IDLENGTH = 10;

    private static final char[] S_BASE64CHAR = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
            'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',
            'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3',
            '4', '5', '6', '7', '8', '9', '+', '/' };

    /**
     * 随机产生指定长度的随机字符串
     *
     * @param length int 指定生成字符串的长度
     * @return 随机字符串
     */
    private static String getRandomString(int length) {
        String base = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        Random random = new Random();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < length; i++) {
            int number = random.nextInt(base.length());
            sb.append(base.charAt(number));
        }
        sb.append(getTime());
        return encode(sb.toString().getBytes(), 1, 9);

    }

    @SuppressWarnings({ "SameParameterValue", "Annotation" })
    private static String encode(byte[] data, int off, int len) {
        if (len <= 0) {
            return "";
        }
        char out[] = new char[(len / 3) * 4 + 4];
        int rindex = off;
        int windex = 0;
        int rest;
        for (rest = len; rest >= 3; rest -= 3) {
            int i = ((data[rindex] & 0xff) << 16) + ((data[rindex + 1] & 0xff) << 8) + (data[rindex + 2] & 0xff);
            out[windex++] = S_BASE64CHAR[i >> 18];
            out[windex++] = S_BASE64CHAR[i >> 12 & 0x3f];
            out[windex++] = S_BASE64CHAR[i >> 6 & 0x3f];
            out[windex++] = S_BASE64CHAR[i & 0x3f];
            rindex += 3;
        }
        if (rest == 1) {
            int i = data[rindex] & 0xff;
            out[windex++] = S_BASE64CHAR[i >> 2];
            out[windex++] = S_BASE64CHAR[i << 4 & 0x3f];
            out[windex++] = '=';
            out[windex++] = '=';
        } else if (rest == 2) {
            int i = ((data[rindex] & 0xff) << 8) + (data[rindex + 1] & 0xff);
            out[windex++] = S_BASE64CHAR[i >> 10];
            out[windex++] = S_BASE64CHAR[i >> 4 & 0x3f];
            out[windex++] = S_BASE64CHAR[i << 2 & 0x3f];
            out[windex++] = '=';
        }
        return new String(out, 0, windex);
    }

    /**
     * 获取日期字符串，格式：20151027123026
     *
     * @return String
     */
    private static String getDateTime() {
        SimpleDateFormat df = new SimpleDateFormat("yyyyMMddHHmmss");
        return df.format(new Date());
    }

    /**
     * 获取日期字符串，格式：151027
     *
     * @return String
     */
    private static String getDate() {
        SimpleDateFormat df = new SimpleDateFormat("yyMMdd");
        return df.format(new Date());
    }

    /**
     * 获取时间字符串（时分秒），格式：153010
     *
     * @return 时间字符串（时分秒），格式：153010
     */
    private static String getTime() {
        SimpleDateFormat df = new SimpleDateFormat("HHmmss");
        return df.format(new Date());
    }
}