随机生成指定长度String

喜欢ヅ旅行 2022-06-03 02:24 205阅读 0赞

**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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