java regex search replace issue

Question

Hi all,

I am new to java regex.

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

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

Example:

Existing string:

aaaa^
TEST^x^^y^z^""^cccc^bbb^
bbbb^
TEST^p^^q^r^""^lll^mmm^
TEST^P^X^q^n^""^hhh^ttt^

Expected string:

aaaa^
TEST^x^^y^z^^cccc^bbb^
bbbb^
TEST^p^^q^r^^lll^mmm^
TEST^NOT EMPTY THUS IGNORE^X^q^n^""^hhh^ttt^

How do I do it.

Any help is highly appreciated.

Thanks in advance.

Answer 1

String resultString = subjectString.replaceAll("(TEST\\^[^^]*\\^\\^[^^]*\\^[^^]*\\^)\"\"\^", "$1");

Explanation:

(       # start capturing group
 TEST   # match TEST
 \^     # match ^ (no. 1)
 [^^]*  # match 0 or more non-^ characters
 \^\^   # match ^^ (no. 2 and 3)
 [^^]*  # match 0 or more non-^ characters
 \^     # match ^ (no. 4)
 [^^]*  # match 0 or more non-^ characters
 \^     # match ^ (no. 5)
)       # end capturing group
""      # match ""
\^      # match ^ (no. 6)

Answer 2

^ is the delimiter, so you could split the string into tokens:

String[] tokens = text.split("\\^", -1);

Then search through that array of tokens looking for TEST, applying whatever logic you need, updating the tokens as needed.

Finally, output the updated list of tokens, separated by ^:

for (int i=0; i<tokens.length; i++) {
    if (i > 0) {
        System.out.print("^");
    }
    System.out.print(tokens[i]);
}
System.out.println();

Doing it this way, the algorithm you are implementing will be much clearer.

Answer 3

Tim's answer is almost correct. However there can be case where after "" there is no 6th ^ but some other character. The correction is

String resultString = subjectString.replaceAll("(TEST\\^[^^]*\\^\\^[^^]*\\^[^^]*\\^)\"\"\\^", "$1^");