随机生成指定长度String

工作中需要生成随机String,研究了一下,

我用时间的Long生成62进制的数 -> 按照需求随机String长度拼接，返回

代码如下：

类：RandomGeneration，Long.toString()这个方法是可以转化为2-36进制，下一个类LongToStringMax62补充转化为62进制

import java.text.SimpleDateFormat;import java.util.Date;import java.util.Random;import java.util.UUID;import org.slf4j.Logger;import org.slf4j.LoggerFactory;public class RandomGeneration {private static final Logger logger = LoggerFactory.getLogger(RandomGeneration.class);//  定义所有的字符组成的串final static char[] allChar = {        '0' , '1' , '2' , '3' , '4' , '5' ,        '6' , '7' , '8' , '9' , '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'     };    final static char[] allCharUpper = {        '0' , '1' , '2' , '3' , '4' , '5' ,        '6' , '7' , '8' , '9' , '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'     };    final static char[] allCharLower = {        '0' , '1' , '2' , '3' , '4' , '5' ,        '6' , '7' , '8' , '9' , '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'    };    //  定义所有的小写字符组成的串（不包括数字）    final static char[] letterChar = {        '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'     };    final static char[] letterCharUpper = {        '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'     };    final static char[] letterCharLower = {        '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'    };    //  定义所有的数字字符组成的串    final static char[] numberChar = {        '0' , '1' , '2' , '3' , '4' , '5' ,        '6' , '7' , '8' , '9'    };    /**     * 生成长度为length的随机字符串（包括字母和数字）     * @param length需要生成的字符串长度     * @param flag需要生成的字符大小写转换：0不变；1大写；2小写;其它不变     * @return     */    public static String generateStrToLength(int length, int flag) {        StringBuffer respStr = new StringBuffer();        Random random = new Random();        if(0 == flag) {        for (int i = 0; i < length; i++) {        respStr.append(allChar[random.nextInt(62)]);            }        }else if(1 == flag) {        for (int i = 0; i < length; i++) {        respStr.append(allCharUpper[random.nextInt(36)]);            }        }else if(2 == flag) {        for (int i = 0; i < length; i++) {        respStr.append(allCharLower[random.nextInt(36)]);            }        }else{        for (int i = 0; i < length; i++) {        respStr.append(allChar[random.nextInt(62)]);            }        }        return respStr.toString();    }        /**     * 产生长度为length的随机字符串（只包括字母）     * @param length需要生成的字符串长度     * @param flag需要生成的字符大小写转换：0不变；1大写；2小写;其它不变     * @return     */    public static String generateLetterStrToLength(int length, int flag) {        StringBuffer respStr = new StringBuffer();        Random random = new Random();        if(0 == flag) {        for (int i = 0; i < length; i++) {        respStr.append(letterChar[random.nextInt(52)]);            }        }else if(1 == flag) {        for (int i = 0; i < length; i++) {        respStr.append(letterCharUpper[random.nextInt(26)]);            }        }else if(2 == flag) {        for (int i = 0; i < length; i++) {        respStr.append(letterCharLower[random.nextInt(26)]);            }        }else{        for (int i = 0; i < length; i++) {        respStr.append(letterChar[random.nextInt(52)]);            }        }        return respStr.toString();    }        /**     * 产生长度为length的随机字符串（只包括数字）     * @param length     * @return     */    public static String generateNumberStrToLength(int length) {        StringBuffer respStr = new StringBuffer();        Random random = new Random();    for (int i = 0; i < length; i++) {    respStr.append(numberChar[random.nextInt(10)]);        }        return respStr.toString();    }        /**     * 按照给定字符串随机生成长度为length的字符串     * @param randomString需要随机的String     * @param length需要生成的字符串长度     * @param flag需要生成的字符大小写转换：0不变；1大写；2小写;其它不变     * @return     */    public static String generateStrToLength(String randomString, int length, int flag) {        StringBuffer respStr = new StringBuffer();        Random random = new Random();        for (int i = 0; i < length; i++) {        respStr.append(randomString.charAt(random.nextInt(randomString.length())));        //respStr.append(LongToStringMax62.digits[(random.nextInt(62))]);        }        String respString = respStr.toString();        if(1 == flag) {        respString.toUpperCase();        }else if(2 == flag) {        respString.toLowerCase();        }        return respString;    }        /**     * 返回日期当前转化规定格式String     * @param date     * @param format     * @return     */    public static String generateStrToDate(Object date, String format){    //Date date = new Date();    //"yyMMddHHmmssSSS"    SimpleDateFormat sdf = new SimpleDateFormat(format);return sdf.format(date);    }        /**     * 通过UUID生成String     * @return     */    public static String randomUUID(){    String uuid = java.util.UUID.randomUUID().toString();uuid = uuid.replaceAll("-", "");return uuid;    }        /**     * Math.random()生成String 注：(length > 1 && length < 10)     * @param length(length > 1 && length < 10)     * @return     */    public static String mathRandom(int length){return String.valueOf((int)((Math.random()*9+1)*Math.pow(10, length-1)));    }        /**     * 时间Long转化规定进制长度为Length的String(不满足长度时随机数字大小写字母补全长度)     * Long最大值转化36进制=1y2p0ij32e8e7     *      * @param date时间转化为的Long('Thu Dec 14 09:48:29 CST 2017'转化为36进制为'jb5tsuvz')     * @param base进制(2 <= base <= 36)     * @param length长度(length >= 时间生成的规定进制数的长度,若length < 时间生成的规定进制数的长度 时建议根据实际需求选取其它方法)     * @return     */    public static String generateStrToBase36(Long date, int base, int length){    StringBuffer respStr = new StringBuffer();    respStr.append(Long.toString(date, base));    if(respStr.length() < length){    //logger.info(respStr.toString());    Random random = new Random();    int j = length - respStr.length();    for (int i = 0; i < j; i++) {    respStr.append(allChar[(random.nextInt(62))]);            }    }else if(respStr.length() > length){    StringBuffer respStrLog = new StringBuffer();    //这种情况建议根据实际需求选取其它方法，若看到下面日志输出，请及时更换方法    respStrLog.append("length < ");    respStrLog.append(date);    respStrLog.append("生成的");    respStrLog.append(base);    respStrLog.append("进制数(");    respStrLog.append(respStr);    respStrLog.append(")的长度");    respStrLog.append(respStr.length());    respStrLog.append("，建议根据实际需求选取其它生成方法！！！");    logger.info(respStrLog.toString());    return respStr.substring(respStr.length() - length, respStr.length());    }return respStr.toString();    }        /**     * 时间Long转化规定进制长度为Length的String(不满足长度时随机数字大小写字母补全长度)     * Long最大值转化62进制=aZl8N0y58M7     *      * @param date时间转化为的Long('Thu Dec 14 17:19:29 CST 2017'转化为62进制为'qDLU7DO')     * @param base进制(2 <= base <= 62)     * @param length长度(length >= 时间生成的规定进制数的长度,若length < 时间生成的规定进制数的长度 时建议根据实际需求选取其它方法)     * @return     */    public static String generateStrToBase62(Long date, int base, int length){    StringBuffer respStr = new StringBuffer();    respStr.append(LongToStringMax62.toString(date, base));    if(respStr.length() < length){    //logger.info(respStr.toString());    Random random = new Random();    int j = length - respStr.length();    for (int i = 0; i < j; i++) {    respStr.append(allChar[(random.nextInt(62))]);            }    }else if(respStr.length() > length){    StringBuffer respStrLog = new StringBuffer();    //这种情况建议根据实际需求选取其它方法，若看到下面日志输出，请及时更换方法    respStrLog.append("length < ");    respStrLog.append(date);    respStrLog.append("生成的");    respStrLog.append(base);    respStrLog.append("进制数(");    respStrLog.append(respStr);    respStrLog.append(")的长度");    respStrLog.append(respStr.length());    respStrLog.append("，建议根据实际需求选取其它生成方法！！！");    logger.info(respStrLog.toString());    return respStr.substring(respStr.length() - length, respStr.length());    }return respStr.toString();    }        public static void main(String[] args) {Date date1 = new Date();for (int i = 0 ; i < 10000 ; i++){Date date = new Date();generateStrToBase62(date.getTime(), 62, 15);}Date date2 = new Date();System.out.println("62=" + (date2.getTime() - date1.getTime()));Date date4 = new Date();for (int i = 0 ; i < 10000 ; i++){Date date3 = new Date();generateStrToBase36(date3.getTime(), 36, 15);}Date date5 = new Date();System.out.println("36=" + (date5.getTime() - date4.getTime()));}}

类：LongToStringMax62

public class LongToStringMax62 {/**     * 用于从字符串转换和从字符串转换的最大基数。这个字段的常量值是基数转换方法中允许基数参数的最大值     */    public static final int MAX_RADIX = 62;/** * 将long转化为指定进制 * @param i * @param radix * @return */    public static String toString(long i, int radix) {        if (radix < Character.MIN_RADIX || radix > MAX_RADIX)            radix = 10;        if (radix == 10)            return toString(i);        char[] buf = new char[65];        int charPos = 64;        boolean negative = (i < 0);        if (!negative) {            i = -i;        }        while (i <= -radix) {            buf[charPos--] = RandomGeneration.allChar[(int)(-(i % radix))];            i = i / radix;        }        buf[charPos] = RandomGeneration.allChar[(int)(-i)];        if (negative) {            buf[--charPos] = '-';        }        return new String(buf, charPos, (65 - charPos));    }        /**     * 进制不在2<进制数<62进制或进制为10进制时 进行的操作     * @param i     * @return     */    public static String toString(long i) {        if (i == Long.MIN_VALUE)            return "-9223372036854775808";        int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);        char[] buf = new char[size];        getChars(i, size, buf);        //return new String(buf, true);        return new String(buf);    }        // Requires positive x    static int stringSize(long x) {        long p = 10;        for (int i=1; i<19; i++) {            if (x < p)                return i;            p = 10*p;        }        return 19;    }        /**     * 进制不在2<进制数<62进制或进制为10进制时 进行的操作     */    static void getChars(long i, int index, char[] buf) {        long q;        int r;        int charPos = index;        char sign = 0;        if (i < 0) {            sign = '-';            i = -i;        }        // Get 2 digits/iteration using longs until quotient fits into an int        while (i > Integer.MAX_VALUE) {            q = i / 100;            // really: r = i - (q * 100);            r = (int)(i - ((q << 6) + (q << 5) + (q << 2)));            i = q;            buf[--charPos] = DigitOnes[r];            buf[--charPos] = DigitTens[r];        }        // Get 2 digits/iteration using ints        int q2;        int i2 = (int)i;        while (i2 >= 65536) {            q2 = i2 / 100;            // really: r = i2 - (q * 100);            r = i2 - ((q2 << 6) + (q2 << 5) + (q2 << 2));            i2 = q2;            buf[--charPos] = DigitOnes[r];            buf[--charPos] = DigitTens[r];        }        // Fall thru to fast mode for smaller numbers        // assert(i2 <= 65536, i2);        for (;;) {            q2 = (i2 * 52429) >>> (16+3);            r = i2 - ((q2 << 3) + (q2 << 1));  // r = i2-(q2*10) ...            buf[--charPos] = RandomGeneration.allChar[r];            i2 = q2;            if (i2 == 0) break;        }        if (sign != 0) {            buf[--charPos] = sign;        }    }        final static char [] DigitTens = {        '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',        '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',        '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',        '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',        '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',        '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',        '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',        '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',        '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',        '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',        } ;    final static char [] DigitOnes = {        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',        } ;}

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