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Removing whitespaces at the beginning of the string with Regex gives null Java

I would like to get groups from a string that is loaded from txt file. This file looks something like this (notice the space at the beginning of file):
as431431af,87546,3214| 5a341fafaf,3365,54465 | 6adrT43 , 5678 , 5655
First part of string until first comma can be digits and letter, second part of string are only digits and third are also only digits. After | its all repeating.
First, I load txt file into string :String readFile3 = readFromTxtFile("/resources/file.txt");
Then I remove all whitespaces with regex :
String no_whitespace = readFile3.replaceAll("\\s+", "");
After that i try to get groups :
Pattern p = Pattern.compile("[a-zA-Z0-9]*,\\d*,\\d*", Pattern.MULTILINE);
Matcher m = p.matcher(ue_No_whitespace);
int lastMatchPos = 0;
while (m.find()) {
System.out.println(m.group());
lastMatchPos = m.end();
}
if (lastMatchPos != ue_No_whitespace.length())
System.out.println("Invalid string!");
Now I would like, for each group remove "," and add every value to its variable, but I am getting this groups : (notice this NULL)
nullas431431af,87546,3214
5a341fafaf,3365,54465
6adrT43,5678,5655
What am i doing wrong? Even when i physicaly remove space from the beginning of the txt file , same result occurs.
Is there any easier way to get groups in this string with regex and add each string part, before "," , to its variable?

You can split with | enclosed with optional whitespaces and then split the obtained items with , enclosed with optional whitespaces:
String str = "as431431af,87546,3214| 5a341fafaf,3365,54465 | 6adrT43 , 5678 , 5655";
String[] items = str.split("\\s*\\|\\s*");
List<String[]> res = new ArrayList<>();
for(String i : items) {
String[] parts = i.split("\\s*,\\s*");
res.add(parts);
System.out.println(parts[0] + " - " + parts[1] + " - " + parts[2]);
}
See the Java demo printing
as431431af - 87546 - 3214
5a341fafaf - 3365 - 54465
6adrT43 - 5678 - 5655
The results are in the res list.
Note that
\s* - matches zero or more whitespaces
\| - matches a pipe char

The pattern that you tried only has optional quantifiers * which could also match only comma's.
You also don't need Pattern.MULTILINE as there are no anchors in the pattern.
You can use 3 capture groups and use + as the quantifier to match at least 1 or more occurrence, and after each part either match a pipe | or assert the end of the string $
([a-zA-Z0-9]+),([0-9]+),([0-9]+)(?:\||$)
Regex demo | Java demo
For example
String readFile3 = "as431431af,87546,3214| 5a341fafaf,3365,54465 | 6adrT43 , 5678 , 5655";
String no_whitespace = readFile3.replaceAll("\\s+", "");
Pattern p = Pattern.compile("([a-zA-Z0-9]+),([0-9]+),([0-9]+)(?:\\||$)");
Matcher matcher = p.matcher(no_whitespace);
while (matcher.find()) {
for (int i = 1; i <= matcher.groupCount(); i++) {
System.out.println(matcher.group(i));
}
System.out.println("--------------------------------");
}
Output
as431431af
87546
3214
--------------------------------
5a341fafaf
3365
54465
--------------------------------
6adrT43
5678
5655
--------------------------------

Need to extract data from CSV file

In my file I have below data, everything is string
Input
"abcd","12345","success,1234,out",,"hai"
The output should be like below
Column 1: "abcd"
Column 2: "12345"
Column 3: "success,1234,out"
Column 4: null
Column 5: "hai"
We need to use comma as a delimiter , the null value is comming without double quotes.
Could you please help me to find a regular expression to parse this data

You could try a tool like CSVReader from OpenCsv https://sourceforge.net/projects/opencsv/
You can even configure a CSVParser (used by the reader) to output null on several conditions. From the doc :
/**
* Denotes what field contents will cause the parser to return null: EMPTY_SEPARATORS, EMPTY_QUOTES, BOTH, NEITHER (default)
*/
public static final CSVReaderNullFieldIndicator DEFAULT_NULL_FIELD_INDICATOR = NEITHER;

You can use this Regular Expression
"([^"]*)"
DEMO: https://regex101.com/r/WpgU9W/1
Match 1
Group 1. 1-5 `abcd`
Match 2
Group 1. 8-13 `12345`
Match 3
Group 1. 16-32 `success,1234,out`
Match 4
Group 1. 36-39 `hai`

Using the ("[^"]+")|(?<=,)(,) regex you may find either quoted strings ("[^"]+"), which should be treated as is, or commas preceded by commas, which denote null field values. All you need now is iterate through the matches and check which of the two capture groups defined and output accordingly:
String input = "\"abcd\",\"12345\",\"success,1234,out\",,\"hai\"";
Pattern pattern = Pattern.compile("(\"[^\"]+\")|(?<=,)(,)");
Matcher matcher = pattern.matcher(input);
int col = 1;
while (matcher.find()) {
if (matcher.group(1) != null) {
System.out.println("Column " + col + ": " + matcher.group(1));
col++;
} else if (matcher.group(2) != null) {
System.out.println("Column " + col + ": null");
col++;
}
}
Demo: https://ideone.com/QmCzPE

Step #1:
import java.util.regex.Matcher;
import java.util.regex.Pattern;
final String regex = "(,,)";
final String string = "\"abcd\",\"12345\",\"success,1234,out\",,\"hai\"\n"
+ "\"abcd\",\"12345\",\"success,1234,out\",\"null\",\"hai\"";
final String subst = ",\"null\",";
final Pattern pattern = Pattern.compile(regex);
final Matcher matcher = pattern.matcher(string);
// The substituted value will be contained in the result variable
final String result = matcher.replaceAll(subst);
System.out.println("Substitution result: " + result);
Original Text:
"abcd","12345","success,1234,out",,"hai"
Transformation: (with null)
"abcd","12345","success,1234,out","null","hai"
Step #2: (use REGEXP)
"([^"]*)"
Result:
abcd
12345
success,1234,out
null
hai
Credits:
Emmanuel Guiton [https://stackoverflow.com/users/7226842/emmanuel-guiton] REGEXP

You can also use the Replace function:
final String inuput = "\"abcd\",\"12345\",\"success,1234,out\",,\"hai\"";
System.out.println(inuput);
String[] strings = inuput
.replaceAll(",,", ",\"\",")
.replaceAll(",,", ",\"\",") // if you have more then one null successively
.replaceAll("\",\"", "\";\"")
.replaceAll("\"\"", "")
.split(";");
for (String string : strings) {
String output = string;
if (output.isEmpty()) {
output = null;
}
System.out.println(output);
}

Java String tokens

I have a string line
String user_name = "id=123 user=aron name=aron app=application";
and I have a list that contains: {user,cuser,suser}
And i have to get the user part from string. So i have code like this
List<String> userName = Config.getConfig().getList(Configuration.ATT_CEF_USER_NAME);
String result = null;
for (String param: user_name .split("\\s", 0)){
for(String user: userName ){
String userParam = user.concat("=.*");
if (param.matches(userParam )) {
result = param.split("=")[1];
}
}
}
But the problem is that if the String contains spaces in the user_name, It do not work.
For ex:
String user_name = "id=123 user=aron nicols name=aron app=application";
Here user has a value aron nicols which contain spaces. How can I write a code that can get me exact user value i.e. aron nicols

If you want to split only on spaces that are right before tokens which have = righ after it such as user=... then maybe add look ahead condition like
split("\\s(?=\\S*=)")
This regex will split on
\\s space
(?=\\S*=) which has zero or more * non-space \\S characters which ends with = after it. Also look-ahead (?=...) is zero-length match which means part matched by it will not be included in in result so split will not split on it.
Demo:
String user_name = "id=123 user=aron nicols name=aron app=application";
for (String s : user_name.split("\\s(?=\\S*=)"))
System.out.println(s);
output:
id=123
user=aron nicols
name=aron
app=application
From your comment in other answer it seems that = which are escaped with \ shouldn't be treated as separator between key=value but as part of value. In that case you can just add negative-look-behind mechanism to see if before = is no \, so (?<!\\\\) right before will require = to not have \ before it.
BTW to create regex which will match \ we need to write it as \\ but in Java we also need to escape each of \ to create \ literal in String that is why we ended up with \\\\.
So you can use
split("\\s(?=\\S*(?<!\\\\)=)")
Demo:
String user_name = "user=Dist\\=Name1, xyz src=activedirectorydomain ip=10.1.77.24";
for (String s : user_name.split("\\s(?=\\S*(?<!\\\\)=)"))
System.out.println(s);
output:
user=Dist\=Name1, xyz
src=activedirectorydomain
ip=10.1.77.24

Do it like this:
First split input string using this regex:
" +(?=\\w+(?<!\\\\)=)"
This will give you 4 name=value tokens like this:
id=123
user=aron nicols
name=aron
app=application
Now you can just split on = to get your name and value parts.
Regex Demo
Regex Demo with escaped =

CODE FISH, this simple regex captures the user in Group 1: user=\\s*(.*?)\s+name=
It will capture "Aron", "Aron Nichols", "Aron Nichols The Benevolent", and so on.
It relies on the knowledge that name= always follows user=
However, if you're not sure that the token following user is name, you can use this:
user=\s*(.*?)(?=$|\s+\w+=)
Here is how to use the second expression (for the first, just change the string in Pattern.compile:
String ResultString = null;
try {
Pattern regex = Pattern.compile("user=\\s*(.*?)(?=$|\\s+\\w+=)", Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE);
Matcher regexMatcher = regex.matcher(subjectString);
if (regexMatcher.find()) {
ResultString = regexMatcher.group(1);
}
} catch (PatternSyntaxException ex) {
// Syntax error in the regular expression
}

How to remove special characters from input text

I want to remove all special characters from input text as well as some restricted words.
Whatever the things I want to remove, that will come dynamically
(Let me clarify this: Whatever the words I need to exclude they will be provided dynamically - the user will decide what needs to be excluded. That is the reason I did not include regex. restricted_words_list (see my code) will get from the database just to check the code working or not I kept statically ),
but for demonstration purposes, I kept them in a String array to confirm whether my code is working properly or not.
public class TestKeyword {
private static final String[] restricted_words_list={"#","of","an","^","#","<",">","(",")"};
private static final Pattern restrictedReplacer;
private static Set<String> restrictedWords = null;
static {
StringBuilder strb= new StringBuilder();
for(String str:restricted_words_list){
strb.append("\\b").append(Pattern.quote(str)).append("\\b|");
}
strb.setLength(strb.length()-1);
restrictedReplacer = Pattern.compile(strb.toString(),Pattern.CASE_INSENSITIVE);
strb = new StringBuilder();
}
public static void main(String[] args)
{
String inputText = "abcd abc# cbda ssef of jjj t#he g^g an wh&at ggg<g ss%ss ### (()) D^h^D";
System.out.println("inputText : " + inputText);
String modifiedText = restrictedWordCheck(inputText);
System.out.println("Modified Text : " + modifiedText);
}
public static String restrictedWordCheck(String input){
Matcher m = restrictedReplacer.matcher(input);
StringBuffer strb = new StringBuffer(input.length());//ensuring capacity
while(m.find()){
if(restrictedWords==null)restrictedWords = new HashSet<String>();
restrictedWords.add(m.group()); //m.group() returns what was matched
m.appendReplacement(strb,""); //this writes out what came in between matching words
for(int i=m.start();i<m.end();i++)
strb.append("");
}
m.appendTail(strb);
return strb.toString();
}
}
The output is :
inputText : abcd abc# cbda ssef of jjj t#he g^g an wh&at ggg
Modified Text : abcd abc# cbda ssef jjj the gg wh&at gggg ss%ss ### (()) DhD
Here the excluded words are of and an, but only some of the special characters, not all that I specified in restricted_words_list
Now I got a better Solution:
String inputText = title;// assigning input
List<String> restricted_words_list = catalogueService.getWordStopper(); // getting all stopper words from database dynamically (inside getWordStopper() method just i wrote a query and getting list of words)
String finalResult = "";
List<String> stopperCleanText = new ArrayList<String>();
String[] afterTextSplit = inputText.split("\\s"); // split and add to list
for (int i = 0; i < afterTextSplit.length; i++) {
stopperCleanText.add(afterTextSplit[i]); // adding to list
}
stopperCleanText.removeAll(restricted_words_list); // remove all word stopper
for (String addToString : stopperCleanText)
{
finalResult += addToString+";"; // add semicolon to cleaned text
}
return finalResult;

public String replaceAll(String regex,
String replacement)
Replaces each substring of this string (which matches the given regular expression) with the given replacement.
Parameters:
regex - the regular expression to which this string is to be
matched
replacement - the string to be substituted for each match.
So you just need to provide replacement parameter with an empty String.

You should change your loop
for(String str:restricted_words_list){
strb.append("\\b").append(Pattern.quote(str)).append("\\b|");
}
to this:
for(String str:restricted_words_list){
strb.append("\\b*").append(Pattern.quote(str)).append("\\b*|");
}
Because with your loop you're matching the restricted_words_list elements only if there is something before and after the match. Since abc# does not have anything after the # it will not be replaced. If you add * (which means 0 or more occurences) to the \\b on either side it will match things like abc# as well.

You may consider to use Regex directly to replace those special character with empty ''? Check it out: Java; String replace (using regular expressions)?, some tutorial here: http://www.vogella.com/articles/JavaRegularExpressions/article.html

You can also do like this :
String inputText = "abcd abc# cbda ssef of jjj t#he g^g an wh&at ggg<g ss%ss ### (()) D^h^D";
String regx="([^a-z^ ^0-9]*\\^*)";
String textWithoutSpecialChar=inputText.replaceAll(regx,"");
System.out.println("Without Special Char:"+textWithoutSpecialChar);
String yourSetofString="of|an"; // your restricted words.
String op=textWithoutSpecialChar.replaceAll(yourSetofString,"");
System.out.println("output : "+op);
o/p :
Without Special Char:abcd abc cbda ssef of jjj the gg an what gggg ssss h
output : abcd abc cbda ssef jjj the gg what gggg ssss h

String s = "abcd abc# cbda ssef of jjj t#he g^g an wh&at ggg (blah) and | then";
String[] words = new String[]{ " of ", "|", "(", " an ", "#", "#", "&", "^", ")" };
StringBuilder sb = new StringBuilder();
for( String w : words ) {
if( w.length() == 1 ) {
sb.append( "\\" );
}
sb.append( w ).append( "|" );
}
System.out.println( s.replaceAll( sb.toString(), "" ) );

replaceFirst for character "`"

First time here. I'm trying to write a program that takes a string input from the user and encode it using the replaceFirst method. All letters and symbols with the exception of "`" (Grave accent) encode and decode properly.
e.g. When I input
`12
I am supposed to get 28AABB as my encryption, but instead, it gives me BB8AA2
public class CryptoString {
public static void main(String[] args) throws IOException, ArrayIndexOutOfBoundsException {
String input = "";
input = JOptionPane.showInputDialog(null, "Enter the string to be encrypted");
JOptionPane.showMessageDialog(null, "The message " + input + " was encrypted to be "+ encrypt(input));
public static String encrypt (String s){
String encryptThis = s.toLowerCase();
String encryptThistemp = encryptThis;
int encryptThislength = encryptThis.length();
for (int i = 0; i < encryptThislength ; ++i){
String test = encryptThistemp.substring(i, i + 1);
//Took out all code with regard to all cases OTHER than "`" "1" and "2"
//All other cases would have followed the same format, except with a different string replacement argument.
if (test.equals("`")){
encryptThis = encryptThis.replaceFirst("`" , "28");
}
else if (test.equals("1")){
encryptThis = encryptThis.replaceFirst("1" , "AA");
}
else if (test.equals("2")){
encryptThis = encryptThis.replaceFirst("2" , "BB");
}
}
}
I've tried putting escape characters in front of the grave accent, however, it is still not encoding it properly.

Take a look at how your program works in each loop iteration:
i=0
encryptThis = '12 (I used ' instead of ` to easier write this post)
and now you replace ' with 28 so it will become 2812
i=1
we read character at position 1 and it is 1 so
we replace 1 with AA making 2812 -> 28AA2
i=2
we read character at position 2, it is 2 so
we replace first 2 with BB making 2812 -> BB8AA2
Try maybe using appendReplacement from Matcher class from java.util.regex package like
public static String encrypt(String s) {
Map<String, String> replacementMap = new HashMap<>();
replacementMap.put("`", "28");
replacementMap.put("1", "AA");
replacementMap.put("2", "BB");
Pattern p = Pattern.compile("[`12]"); //regex that will match ` or 1 or 2
Matcher m = p.matcher(s);
StringBuffer sb = new StringBuffer();
while (m.find()){//we found one of `, 1, 2
m.appendReplacement(sb, replacementMap.get(m.group()));
}
m.appendTail(sb);
return sb.toString();
}

encryptThistemp.substring(i, i + 1); The second parameter of substring is length, are you sure you want to be increasing i? because this would mean after the first iteration test would not be 1 character long. This could throw off your other cases which we cannot see!