It is easy to check a string with regular expression, but there is no direct method to generate string from regular expression. I hardly need it but found nothing. So I myself generated the following program to generate string using regular expression and check back the string with given regular expression. The program i generated will sufficient for normal expression. It will cover my back. It will not parse high level expression.
Output example using random regex generator
Regex: [a-z][a-z0-9]{8,10}@[a-z0-9]{5,9}.com
Matches: [a-z][a-z0-9]{8,10}@[a-z0-9]{5,9}.com, String: bak65qvkpp@3qosue.com, Length: 21
Regex: [\w][\D]{0,10}[\d\W]{1,10}[abc.][abc09]{1,10}
Matches: [\w][\D]*[\d\W]+[abc.][abc09]+, String: aLchJL,e’‘.c9bca, Length: 16
Regex: [A-Z]{4}-#%[\d]{3}
Matches: [A-Z]{4}-#%[\d]{3}, String: BAKZ-#%114, Length: 10
Regex: www.[a-z][a-z0-9-_]{5,15}[a-z].com
Matches: www.[a-z][a-z0-9-_]{5,15}[a-z].com, String: www.jj829x10cq9ngilk.com, Length: 24
Regex: 01[7856][0-9]{2}-[0-9]{6}
Matches: 01[7856][0-9]{2}-[0-9]{6}, String: 01700-736202, Length: 12
StringRegex.java (main class)
import java.util.Random; import java.util.regex.Matcher; import java.util.regex.Pattern; /** * * @author Pritom K Mondal * @version 1.0 */ public class StringRegex { public static void main(String[] args) { String regex = "[a-z][a-z0-9]{8,10}@[a-z0-9]{5,9}.com"; StringRegex.stringFromRegex(regex); regex = "[\\w][\\D]*[\\d\\W]+[abc.][abc09]+"; StringRegex.stringFromRegex(regex); regex = "[A-Z]{4}-#%[\\d]{3}"; StringRegex.stringFromRegex(regex); regex = "www.[a-z][a-z0-9-_]{5,15}[a-z].com"; StringRegex.stringFromRegex(regex); regex = "01[7856][0-9]{2}-[0-9]{6}"; StringRegex.stringFromRegex(regex); } public static void stringFromRegex(String regex) { String regexConverted = cvtLineTerminators(regex); System.out.println("Regex: " + regexConverted); String fullString = ""; fullString = parse(regexConverted, ""); if(fullString.matches(regex)) { System.out.println("Matches: " + regex + ", String: " + fullString + ", Length: " + fullString.length()); } else { System.err.println("Matches Failed: " + regex + ", String: " + fullString + ", :Length: " + fullString.length()); } System.out.println("\n\n"); } private static String parse(String regex, String fullString) { Random random = new Random(); if(regex.trim().length() > 0) { Boolean allow = false, processed = false; if(regex.startsWith("[") && (regex.substring(0, regex.indexOf("]") + 1).matches("(.*)[a-z]\\-[a-z](.*)") || regex.substring(0, regex.indexOf("]") + 1).matches("(.*)[A-Z]\\-[A-Z](.*)") || regex.substring(0, regex.indexOf("]") + 1).matches("(.*)d(.*)") || regex.substring(0, regex.indexOf("]") + 1).matches("(.*)D(.*)") || regex.substring(0, regex.indexOf("]") + 1).matches("(.*)w(.*)") || regex.substring(0, regex.indexOf("]") + 1).matches("(.*)W(.*)") || regex.substring(0, regex.indexOf("]") + 1).matches("\\[([a-z]*)([0-9]*).\\]") || regex.substring(0, regex.indexOf("]") + 1).matches("\\[[A-Z].\\]") || regex.substring(0, regex.indexOf("]") + 1).matches("(.*)[0-9]\\-[0-9](.*)"))) { allow = true; } if(allow) { int start = regex.indexOf("["); int end = regex.indexOf("]", start); String part = regex.substring(start, end + 1); regex = regex.substring(end + 1); int pos1 = 1, pos2 = 1; if(regex.startsWith("{")) { start = 0; String pos = ""; end = regex.indexOf("}", start); pos = regex.substring(start + 1, end); //part = part + regex.substring(start, end + 1); regex = regex.substring(end + 1); if(pos.trim().length() > 0) { if(pos.contains(",")) { String[] poss = pos.split(","); pos1 = Integer.parseInt(poss[0]); pos2 = Integer.parseInt(poss[1]); } else { pos1 = Integer.parseInt(pos); pos2 = Integer.parseInt(pos); } } } //System.out.println("Pos: " + pos1 + " to " + pos2); StringBuilder sb = new StringBuilder(); String str = ""; String printInfo = "Processing-1: " + part; int tried = 0; while(sb.toString().length() == 0 && tried <= 5) { tried++; str = RandomString.nextString(2000); try { Matcher m = Pattern.compile(part).matcher(str); while (m.find()) { sb.append(m.group(0).toString()); } } catch (Exception ex) { System.out.println("Exception: " + ex.getMessage()); } } if(sb.toString().length() > 0) { processed = true; str = sb.toString(); while(true) { if(str.length() < pos2) { str = str.concat(str); } else { break; } } printInfo += " = (" + pos1 + ", " + pos2 + "): "; String cutString = str.substring(0, pos1); if(pos2 - pos1 > 0) { pos2 = random.nextInt(pos2 - pos1); cutString += str.substring(pos1, pos2 + pos1); } printInfo += cutString; //System.out.println(printInfo); fullString += cutString; } else { regex = part + regex; } } if(regex.startsWith("[") && !processed) { processed = true; int start = regex.indexOf("["); int end = regex.indexOf("]", start); String part = regex.substring(start + 1, end); regex = regex.substring(end + 1); String printInfo = "Processing-2: " + part; int pos1 = 1, pos2 = 1; if(regex.startsWith("{")) { start = 0; String pos = ""; end = regex.indexOf("}", start); pos = regex.substring(start + 1, end); regex = regex.substring(end + 1); if(pos.trim().length() > 0) { if(pos.contains(",")) { String[] poss = pos.split(","); pos1 = Integer.parseInt(poss[0]); pos2 = Integer.parseInt(poss[1]); } else { pos1 = Integer.parseInt(pos); pos2 = Integer.parseInt(pos); } } } String pushString = ""; for(int i = 0; i < pos1; i++) { pushString += part; } if(pos2 - pos1 > 0) { pos2 = random.nextInt(pos2 - pos1); for(int i = 0; i < pos2; i++) { pushString += part; } } printInfo += "{" + pos1 + "," + pos2 + "} = " + pushString; //System.out.println(printInfo); fullString += pushString; } if(!processed) { //System.out.println("Handled: " + regex); regex = "[" + regex; int fa = regex.indexOf("]"), f2 = regex.indexOf("{"), f3 = regex.indexOf("[", 1); if(fa > f3) fa = f3; if(fa > f2) fa = f2; if(fa < 0) { if(f2 < f3 && f2 >= 0) { fa = f2; } else if(f3 > f2 && f3 >= 0) { fa = f3; } else { fa = regex.length(); } } //regex = regex.substring(0, fa) + "]" + regex.substring(fa); regex = regex.substring(0, 2) + "]" + regex.substring(2); //System.out.println("Handled: " + regex); } fullString = parse(regex, fullString); } return fullString; } private static String cvtLineTerminators (String s) { s = s.replaceAll("\\*", "{0,10}"); s = s.replaceAll("\\+", "{1,10}"); StringBuffer sb = new StringBuffer (); int oldindex = 0, newindex; while ((newindex = s.indexOf ("\\n", oldindex)) != -1) { sb.append (s.substring (oldindex, newindex)); oldindex = newindex + 2; sb.append ('\n'); } sb.append (s.substring (oldindex)); s = sb.toString (); sb = new StringBuffer (); oldindex = 0; while ((newindex = s.indexOf ("\\r", oldindex)) != -1) { sb.append (s.substring (oldindex, newindex)); oldindex = newindex + 2; sb.append ('\r'); } sb.append (s.substring (oldindex)); s = sb.toString (); sb = new StringBuffer (); oldindex = 0; while ((newindex = s.indexOf ("\\s", oldindex)) != -1) { sb.append (s.substring (oldindex, newindex)); oldindex = newindex + 2; sb.append (" "); } sb.append (s.substring (oldindex)); return sb.toString(); } }
RandomString.java
import java.util.Random; /** * * @author Pritom K Mondal */ public class RandomString { private static final char[] symbols = new char[10 + 26 + 26 + 3 + 8]; private static final char[] chars = new char[52]; private static final char[] numbers = new char[10]; static { for (int idx = 0; idx < 10; ++idx) { numbers[idx] = (char) ('0' + idx); } for (int idx = 10; idx < 36; ++idx) { chars[idx - 10] = (char) ('a' + idx - 10); } for (int idx = 36; idx < 62; ++idx) { chars[idx - 10] = (char) ('A' + idx - 36); } /** * String */ int total = 0; for(int idx = 48; idx <= 57; idx++, total++) { symbols[total] = (char) idx; }// 10 (10) for(int idx = 65; idx <= 90; idx++, total++) { symbols[total] = (char) idx; } // 26 (36) for(int idx = 97; idx <= 122; idx++, total++) { symbols[total] = (char) idx; } // 26 (62) for(int idx = 44; idx <= 46; idx++, total++) { symbols[total] = (char) idx; } // 3 (65) int[] copyFrom = { 64, 95, 44, 46, 45, 145, 146, 35 }; //@ _ , . - ‘ ’ # for(int idx = 0; idx < copyFrom.length; idx++, total++) { symbols[total] = (char) copyFrom[idx]; } // 8 (73) //System.out.println(total); } private static Random random = new Random(); private static char[] buf; public static String fullString() { return new String(symbols); } public static String nextString(int length) { if (length < 1) { throw new IllegalArgumentException("length < 1: " + length); } buf = new char[length]; //System.out.println(symbols); for (int idx = 0; idx < buf.length; ++idx) { buf[idx] = symbols[random.nextInt(symbols.length)]; } return new String(buf); } public static String nextNumber(int length) { if (length < 1) { throw new IllegalArgumentException("length < 1: " + length); } buf = new char[length]; for (int idx = 0; idx < buf.length; ++idx) { buf[idx] = numbers[random.nextInt(numbers.length)]; } return new String(buf); } public static String nextCharacter(int length) { if (length < 1) { throw new IllegalArgumentException("length < 1: " + length); } buf = new char[length]; for (int idx = 0; idx < buf.length; ++idx) { buf[idx] = chars[random.nextInt(chars.length)]; } return new String(buf); } }
