随机生成指定长度String
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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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