java regex - searching for empty content between two occurences of a search char

Question

Hi all,

I am new to java regex.

Sorry for the long posting.

I have a three requirements:

1a) I have a string that contains three occurences of the word 'TEST'. Each of this word is followed by ^ and I need to check if the content between 2 and and 3rd occurence of ^ is blank, if it is blank/empty search further to see if the content between the 5th and 6th occurence of the ^ is "" If it is "", then replace it to be blank/empty Example: Existing string:

aaaa^ 
TEST^x^^y^z^""^cccc^bbb^ 

Expected string:

aaaa^ 
TEST^x^^y^z^^cccc^bbb^ 

1b) If the content between 2nd and 3rd occurence of ^ is not blank and not "", then do not change the content between 5th anc 6th occurence

Existing string:

TEST^p^^q^r^""^lll^mmm^ 

Expected string:

TEST^p^^q^r^""^lll^mmm^

I need to repeat this logic check whenever TEST word is found.

1c) If the content between 5th and 6th occurence of ^ is not blank and not "" and if the content between 2nd and 3rd is blank/empty then replace it with STR.

Existing string:

TEST^g^^q^r^YYY^lll^mmm^ 

Expected string:

TEST^g^STR^q^r^YYY^lll^mmm^ 

I need to accomplish allt he above cases in a java regex. I could make case 1 work BASED ON valuable input from my previous posting in this forum. I could not make case 2 and 3 work.

How to accomplish case 2 and 3 in the same regex expression ( I am not sure as what the regex expressions are for not empty contnet check and for 'OR' check). In non regex world, in plain if else approach, I can take care of the 3 cases as follows:

if (the content between 2nd and 3rd occurence of ^ is empty) 
{ 

if(content between 5th and 6th occurence of ^ is "") 
{ 
make this content empty 
} 
else 
{ 
set the content between 2nd and 3rd occurence of ^ as STR 
} 


} 

But since I need to make this check for each line which starts with the word TEST in the String, I am leaning towards regex.

So far the regex that works for case 1 is as follows:

str.replaceAll("(TEST\\^[^^]*\\^\\^[^^]*\\^[^^]*\\^)\"\"", "$1") 

For 2nd case, I tried modifying the above regex as follows but in vain(Tried to search for not empty VALUE BETWEEN 2ND AND 3RD OCCURENCE where i asSumed *\\d0$ represents EMPTY and [\\d0$] implies NOT EMPTY):

str.replaceAll("(TEST\\^[^^]*\\^[^\\d0$]\\^[^^]*\\^[^^]*\\^)\"\"", "$1") 

Any help to come up with regex expression that takes care of the above 3 usecases is highly appreciated as I have a deadline to meet for this task.

Any help is HIGHLY appreciated.

Thanks in advance.

Answer 1

Hi, Ill first try to solve your (1b) problem. I am sorry but I think you forgot to mention what action should be taken in (1b) if content between 2nd and 3rd occurance of ^ IS BLANK.

1b) If the content between 2nd and 3rd occurence of ^ is not blank and not "", then do not change the content between 5th anc 6th occurence

Answer 2

It looks to me, that ^ is a delimiter. So It could make life much easier if you just split the String at the delimiter and work with array:

List<String> lines = FileUtils(myFile, myEncoding);
List<String[]> allValues = new ArrayList<String[]>();
for (String line: lines)
    allValues.add(line.split("\\^"));

The above example shows a method to process a whole csv file using apache-commons-io.

Answer 3

I have updated the code for your new requirement. ^ and | both have special meaning in regex, so if your delimiter is one of the special character, it needs to be handled more carefully. The new code is

public class Main {

    public static void main(String[] args) {
        System.out.println(replace("TEST^x^^y^z^\"\"^cccc^bbb^", '^'));//case 1a
        System.out.println(replace("TEST^x^^y^z^\"\"Something^cccc^bbb^", '^'));//case 1a
        System.out.println(replace("TEST^x^^y^z^Something\"\"^cccc^bbb^", '^'));//case 1a
        System.out.println(replace("TEST^x^Something^y^z^\"\"^cccc^bbb^", '^'));//case 1b
        System.out.println(replace("TEST^x^^y^z^\"Something\"^cccc^bbb^", '^'));//case 1c

        System.out.println(replace("TEST|x||y|z|\"\"|cccc|bbb|", '|'));//case 1a
        System.out.println(replace("TEST|x||y|z|\"\"Something|cccc|bbb|", '|'));//case 1a
        System.out.println(replace("TEST|x||y|z|Something\"\"|cccc|bbb|", '|'));//case 1a
        System.out.println(replace("TEST|x|Something|y|z|\"\"|cccc|bbb|", '|'));//case 1b
        System.out.println(replace("TEST|x||y|z|\"Something\"|cccc|bbb|", '|'));//case 1c
    }

    /*
    private static String replace(String in) {
        String intermediateResult = in.replaceAll("(TEST\\^[^^]*\\^\\^[^^]*\\^[^^]*\\^)\"\"\\^", "$1^");
        String finalResult = intermediateResult.replaceAll(
                "(TEST\\^[^^]*\\^)(\\^[^^]*\\^[^^]*\\^([^\"\\^].*|\"[^\"].*))", "$1STR$2");
        return finalResult;
    }*/

    private static String replace(String in, char deliminator) {
        String delim = "\\"+deliminator;
        String intermediateResult = in.replaceAll(
                "(TEST" + delim +
                "[^" + delim + "]*" +
                delim + delim +
                "[^" + delim + "]*" + delim +
                "[^" + delim + "]*" + delim +
                ")\"\"" + delim,
                "$1"+deliminator);

        String finalResult = intermediateResult.replaceAll(
                "(TEST" + delim +
                "[^" + delim + "]*" 
                + delim + ")(" + delim +
                "[^" + delim + "]*" + delim +
                "[^" + delim + "]*" + delim +
                "([^\"" + delim + "].*|\"[^\"].*))", "$1STR$2");
        return finalResult;
    }
}

the output is

TEST^x^^y^z^^cccc^bbb^
TEST^x^^y^z^""Something^cccc^bbb^
TEST^x^STR^y^z^Something""^cccc^bbb^
TEST^x^Something^y^z^""^cccc^bbb^
TEST^x^STR^y^z^"Something"^cccc^bbb^
TEST|x||y|z||cccc|bbb|
TEST|x||y|z|""Something|cccc|bbb|
TEST|x|STR|y|z|Something""|cccc|bbb|
TEST|x|Something|y|z|""|cccc|bbb|
TEST|x|STR|y|z|"Something"|cccc|bbb|

Answer 4

Don't use a regex to parse this use a split eg

var arr;
arr=str.split("\^","g");

and perform the logic you describe on each appropriate item in the the resulting array.

Apologies if my java syntax is not correct!