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.
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
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();
}
}
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);
}
}
