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Partially mask data of a group of number using regex

I would like to partially mask data using regex. Here is the input :
123-12345-1234567
And here is what I'd like as output :
1**-*****-*****67
I figure out how to replace for the last group but I don't know to do for the rest of the data.
String s = "123-12345-1234567";
System.out.println(s.replaceAll("\\d(?=\\d{2})", "*")); // output is *23-***45-*****67
Also, I'd like to use only regex because I have different type of data, so different type of mask. I don't want to create functions for each type of data.
For example :
AAAAAAAAA // becomes ********AA
12334567 // becomes 123******
Thanks for your help !

We can use the following regex replacement approach:
String input = "123-12345-1234567";
String output = input.substring(0, 1) +
input.substring(1, input.length()-2).replaceAll("\\d", "*") +
input.substring(input.length()-2);
System.out.println(output); // 1**-*****-*****67
Here we concatenate together the first digit, followed by the middle portion with all digits replaced by *, along with the final two digits.
Edit: A pure regex solution, which, however, is more lines of code than the above and might be less performant.
String input = "123-12345-1234567";
String pattern = "^(\\d)(.*)(\\d{2})$";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(input);
if (m.find()) {
String output = m.group(1) + m.group(2).replaceAll("\\d", "*") + m.group(3);
System.out.println(output); // 1**-*****-*****67
}

Java supports a fixed quantifier in a lookbehind, so what you might do is use a pattern with an alternation to account for the different scenario's if you must use a regex only.
Using the lookarounds you can select a single character to be replaced by *
Note that this is hard to maintain, and it would be a better option to write separate functions for the different data formats using separate patterns or string functions (perhaps accompanied by unit tests)
(?<=^\d{3,7})\d(?=\d*$)|(?<=^[A-Z]{0,6})[A-Z](?=[A-Z]*$)|\d(?<=^\d{2,3})(?=\d?-\d{5}-\d{7}$)|\d(?<=^\d{3}-\d{1,5}(?:-\d{1,5})?)
The separate parts match:
(?<=^\d{3,7})\d(?=\d*$) Match a digit asserting 3-7 digits to the left and only digits to the right
| Or
(?<=^[A-Z]{0,6})[A-Z](?=[A-Z]*$) Match A-Z asserting 0-6 chars to the left and only chars A-Z to the right
| Or
\d(?<=^\d{2,3})(?=\d?-\d{5}-\d{7}$) Match a digit asserting 2-3 digits to the left and optional digit, - with 5 digits and - with 7 digits to the right
| Or
\d(?<=^\d{3}-\d{1,5}(?:-\d{1,5})?) Match a digit asserting 3 digits to the left followed - and 1-5 digits and optionally - with 1-5 digits
Regex demo | Java demo
String regex = "(?<=^\\d{3,7})\\d(?=\\d*$)|(?<=^[A-Z]{0,6})[A-Z](?=[A-Z]*$)|\\d(?<=^\\d{2,3})(?=\\d?-\\d{5}-\\d{7}$)|\\d(?<=^\\d{3}-\\d{1,5}(?:-\\d{1,5})?)";
String s1 = "123-12345-1234567";
String s2 = "AAAAAAAAA";
String s3 = "12334567";
System.out.println(s1.replaceAll(regex, "*"));
System.out.println(s2.replaceAll(regex, "*"));
System.out.println(s3.replaceAll(regex, "*"));
Output
1**-*****-*****67
*******AA
123*****

public static void main(String[] args) {
System.out.println("123-12345-1234567".replaceAll("(?<=.{1,})\\d(?=.{3,})", "*"));
System.out.println("AAAAAAAAA".replaceAll(".(?=.{2,})", "*"));
System.out.println("12334567".replaceAll("(?<=.{3,}).", "*"));
}
output:
1**-*****-*****67
*******AA
123*****

Regex capturing groups within logical OR

I have a set of strings I need to parse and extract values from. They look like:
/apple/1212d3fe
/cat/23224a2f4
/auto/445478eefd
/somethingelse/1234fded
It should match only apple, cat and auto. The output I expect is:
1212, d3fe
23224, a2f4
445478, eefd
null
I need to come up with a regex capturing groups to do the same. I am able to extract the second part but not the first one. The closest I came up with is:
String r2 = "^/(apple/[0-9]{4}|cat/[0-9]{5}|auto/[0-9]{6})([a-f0-9]{4})$";
System.out.println(r2);
Pattern pattern2 = Pattern.compile(r2);
Matcher matcher2 = pattern2.matcher("/apple/2323efff");
if (matcher2.find()) {
System.out.println(matcher2.group(1));
System.out.println(matcher2.group(2));
}
UPDATED QUESTION:
I have a set of strings I need to parse and extract values from. They look like:
/apple/1212d3fe
/cat/23e24a2f4
/auto/df5478eefd
/somethingelse/1234fded
It should match only apple, cat and auto. The output I expect is the everything after the 2nd '/' split as follows: 4 characters if 'apple', 5 characters if 'cat' and 6 characters if 'auto' like:
1212, d3fe
23e24, a2f4
df5478, eefd
null
I need to come up with a regex capturing groups to do the same. I am able to extract the second part but not the first one. The closest I came up with is:
String r2 = "^/(apple/[0-9]{4}|cat/[0-9]{5}|auto/[0-9]{6})([a-f0-9]{4})$";
System.out.println(r2);
Pattern pattern2 = Pattern.compile(r2);
Matcher matcher2 = pattern2.matcher("/apple/2323efff");
if (matcher2.find()) {
System.out.println(matcher2.group(1));
System.out.println(matcher2.group(2));
}
I can do it without the regex OR(|) but it breaks when I include it. Any help with the right regex?

Updated Answer:
As per your updated question you can use this regex based on lookbehind assertions:
/((?<=apple/).{4}|(?<=cat/).{5}|(?<=auto/).{6})(.+)$
RegEx Demo
This regex uses 2 capture groups after matching /
In 1st group we have 3 lookbehind conditions with alternations.
(?<=apple/).{4} makes sure that we match 4 characters that have apple/ on left hand side. Likewise we match 5 and 6 character strings that have cat/ and /auto/.
In 2nd capture group we match remaining characters before end of line.

You could use the regex \/[apple|auto|cat]+\/(\d*)(.*), See here

If you want the last group to have exactly 4 digits you can use this regex:
/(apple|cat|auto)/([0-9a-f]+)([0-9a-f]{4})
Here is a working example:
List<String> strings = Arrays.asList("/apple/1212d3fe", "/cat/23224a2f4", "/auto/445478eefd");
Pattern pattern = Pattern.compile("/(apple|cat|auto)/([0-9a-f]+)([0-9a-f]{4})");
for (String string : strings) {
Matcher matcher = pattern.matcher(string);
if (matcher.find()) {
System.out.println(matcher.group(1));
System.out.println(matcher.group(2));
System.out.println(matcher.group(3));
}
}
If you want for digits after apple, 5 after cat and 6 after auto you can split your algorithm in 2 parts:
List<String> strings = Arrays.asList("/apple/1212d3fe", "/cat/23224a2f4", "/auto/445478eefd", "/some/445478eefd");
Pattern firstPattern = Pattern.compile("/(apple|cat|auto)/([0-9a-f]+)");
for (String string : strings) {
Matcher firstMatcher = firstPattern.matcher(string);
if (firstMatcher.find()) {
String first = firstMatcher.group(1);
System.out.println(first);
int length = getLength(first);
Pattern secondPattern = Pattern.compile("([0-9a-f]{" + length + "})([0-9a-f]{4})");
Matcher secondMatcher = secondPattern.matcher(string);
if (secondMatcher.find()) {
System.out.println(secondMatcher.group(1));
System.out.println(secondMatcher.group(2));
}
}
}
private static int getLength(String key) {
switch (key) {
case "apple":
return 4;
case "cat":
return 5;
case "auto":
return 6;
}
throw new IllegalArgumentException("key not allowed");
}

Replacing consecutive repeated characters in java

I am working on twitter data normalization. Twitter users frequently uses terms like ts I looooooove it in order to emphasize the word love. I want to such repeated characters to a proper English word by replacing repeat characters till I get a proper meaningful word (I am aware that I can not differentiate between good and god by this mechanism).
My strategy would be
identify existence of such repeated strings. I would look for more than 2 same characters, as probably there is no English word with more than two repeat characters.
String[] strings = { "stoooooopppppppppppppppppp","looooooove", "good","OK", "boolean", "mee", "claaap" };
String regex = "([a-z])\\1{2,}";
Pattern pattern = Pattern.compile(regex);
for (String string : strings) {
Matcher matcher = pattern.matcher(string);
if (matcher.find()) {
System.out.println(string+" TRUE ");
}
}
Search for such words in a Lexicon like Wordnet
Replace all but two such repeat characters and check in Lexicon
If not there in the Lexicon remove one more repeat character (Otherwise treat it as misspelling).
Due to my poor Java knowledge I am unable to manage 3 and 4. Problem is I can not replace all but two repeated consecutive characters.
Following code snippet replace all but one repeated characters System.out.println(data.replaceAll("([a-zA-Z])\\1{2,}", "$1"));
Help is required to find out
A. How to replace all but 2 consecutive repeat characters
B. How to remove one more consecutive character from the output of A
[I think B can be managed by the following code snippet]
System.out.println(data.replaceAll("([a-zA-Z])\\1{1,}", "$1"));
Edit: Solution provided by Wiktor Stribiżew works perfectly in Java. I was wondering what changes are required to get the same result in python.
Python uses re.sub.

Your regex ([a-z])\\1{2,} matches and captures an ASCII letter into Group 1 and then matches 2 or more occurrences of this value. So, all you need to replace with a backreference, $1, that holds the value captured. If you use one $1, the aaaaa will be replaced with a single a and if you use $1$1, it will be replaced with aa.
String twoConsecutivesOnly = data.replaceAll(regex, "$1$1");
String noTwoConsecutives = data.replaceAll(regex, "$1");
See the Java demo.
If you need to make your regex case insensitive, use "(?i)([a-z])\\1{2,}" or even "(\\p{Alpha})\\1{2,}". If any Unicode letters must be handled, use "(\\p{L})\\1{2,}".
BONUS: In a general case, to replace any amount of any repeated consecutive chars use
text = text.replaceAll("(?s)(.)\\1+", "$1"); // any chars
text = text.replaceAll("(.)\\1+", "$1"); // any chars but line breaks
text = text.replaceAll("(\\p{L})\\1+", "$1"); // any letters
text = text.replaceAll("(\\w)\\1+", "$1"); // any ASCII alnum + _ chars

/*This code checks a character in a given string repeated consecutively 3 times
if you want to check for 4 consecutive times change count==2--->count==3 OR
if you want to check for 2 consecutive times change count==2--->count==1*/
public class Test1 {
static char ch;
public static void main(String[] args) {
String str="aabbbbccc";
char[] charArray = str.toCharArray();
int count=0;
for(int i=0;i<charArray.length;i++){
if(i!=0 ){
if(charArray[i]==ch)continue;//ddddee
if(charArray[i]==charArray[i-1]) {
count++;
if(count==2){
System.out.println(charArray[i]);
count=0;
ch=charArray[i];
}
}
else{
count=0;//aabb
}
}
}
}
}

Extract letter from String characters and numbers

I have these Strings:
"Turtle123456_fly.me"
"birdy_12345678_prd.tr"
I want the first words of each, ie:
Turtle
birdy
I tried this:
Pattern p = Pattern.compile("//d");
String[] items = p.split(String);
but of course it's wrong. I am not familiar with using Pattern.

Replace the stuff you don't want with nothing:
String firstWord = str.replaceAll("[^a-zA-Z].*", "");
to leave only the part you want.
The regex [^a-zA-Z] means "not a letter", the everything from (and including) the first non-letter to the end is "removed".
See live demo.

String s1 ="Turtle123456_fly.me";
String s2 ="birdy_12345678_prd.tr";
Pattern p = Pattern.compile("^([A-Za-z]+)[^A-Za-z]");
Matcher matcher = p.matcher(s1);
if (matcher.find()) {
System.out.println(matcher.group(1));
}
Explanation:
The first part ^([A-Za-z]+) is a group that captures all the letters anchored to the beginning of the input (using the ^ anchor).
The second part [^A-Za-z] captures the first non-letter, and serves as a terminator for the letters sequence.
Then all we have left to do is to fetch the group with index 1 (group 1 is what we have in the first parenthesis).

maybe you should try this \d+\w+.*

How to count a position of element, relative to another element using regex?

Given String
// 1 2 3
String a = "letters.1223434.more_letters";
I'd like to recognize that numbers come in a 2nd position after the first dot
I then would like to use this knowledge to replace "2nd position of"
// 1 2 3
String b = "someWords.otherwords.morewords";
with "hello" to effectively make
// 1 2 3
String b = "someWords.hello.morewords";
Substitution would have to be done based on the original position of matched element in String a
How can this be done using regex please?

For finding those numbers you can use group mechanism (round brackets in regular expresions):
import java.util.regex.*;
...
String data = "letters.1223434.more_letters";
String pattern="(.+?)\\.(.+?)\\.(.+)";
Matcher m = Pattern.compile(pattern).matcher(data);
if (m.find()) //or while if needed
for (int i = 1; i <= m.groupCount(); i++)
//group 0 == whole String, so I ignore it and start from i=1
System.out.println(i+") [" + m.group(i) + "] start="+m.start(i));
// OUT:
//1) [letters] start=0
//2) [1223434] start=8
//3) [more_letters] start=16
BUT if your goal is just replacing text between two dots try maybe replaceFirst(String regex, String replacement) method on String object:
//find ALL characters between 2 dots once and replace them
String a = "letters.1223434abc.more_letters";
a=a.replaceFirst("\\.(.+)\\.", ".hello.");
System.out.println(a);// OUT => letters.hello.more_letters
regex tells to search all characters between two dots (including these dots), so replacement should be ".hello." (with dots).
If your String will have more dots it will replace ALL characters between first and last dot. If you want regex to search for minimum number of characters necessary to satisfy the pattern you need to use Reluctant Quantifier ->? like:
String b = "letters.1223434abc.more_letters.another.dots";
b=b.replaceFirst("\\.(.+?)\\.", ".hello.");//there is "+?" instead of "+"
System.out.println(b);// OUT => letters.hello.more_letters.another.dots

What you want to do is not directly possible in RegExp, because you cannot get access to the number of the capture group and use this in the replacement operation.
Two alternatives:
If you can use any programming language: Split a using regexp into groups. Check each group if it matches your numeric identifier condition. Split the b string into groups. Replace the corresponding match.
If you only want to use a number of regexp, then you can concatenate a and b using a unique separator (let's say |). Then match .*?\.\d+?\..*?|.*?\.(.*?)\..*? and replace $1. You need to apply this regexp in the three variations first position, second position, third position.

the regex for string a would be
\w+\.(\d+)\.\w+
using the match group to grab the number.
the regex for the second would be
\w+\.(\w+)\.\w+
to grab the match group for the second string.
Then use code like this to do what you please with the matches.
Pattern pattern = Pattern.compile(patternStr);
Matcher matcher = pattern.matcher(inputStr);
boolean matchFound = matcher.find();
where patternStr is the pattern I mentioned above and inputStr is the input string.
You can use variations of this to try each combination you want. So you can move the match group to the first position, try that. If it returns a match, then do the replacement in the second string at the first position. If not, go to position 2 and so on...