Question

I have got dataset like this with three columns

Col1, Col2, Col2

aaa,Arizona DL USTATES,12

bbb,Idaho DL USTATES,35

ccc,Idaho DL USTATES,28

ddd,Wisconsin DL USTATES,11

eeee,Wisconsin DL USTATES,35

What I want to do is that I want to extract the first word of the second column(what is a state name) and put it in the first column.

Expected Output:

Arizona,Arizona randam USTATES,12

Idaho,Idaho randam USTATES,35

Idaho,Idaho randam USTATES,28

Wisconsin,Wisconsin random USTATES,11

The regex that I have is

^[^,]+,([^ ]+) [^\n]+$

With my () I can extract the state name, but How do get the output? What I want is nested parenthesis, something like this

^[^,]+,(([^ ]+) [^\n]+)$

and then the output will be
\1,\2

I should point out that I want to do it using regex replace only.

Edit:

I have solved it by using regex to get all of the state names in a column and then merged it, but I want to know if there are any advanced regex which can be used here.

Answer 1

Your regex with nested parentheses works fine; you just need to use String‘s replaceFirst method and note that Java uses $ for group references. Also note that the groups are enumerated in the order they occur in the regex, so the outer group is $1 because it starts first:

String line = "aaa,Arizona DL USTATES,12";
String result = line.replaceFirst("^[^,]+,(([^ ]+) [^\n]+)$", "$2, $1");
// result is "Arizona, Arizona DL USTATES,12"