How to mark up search keywords regardless of case and without changing the search source word

One day, a great person asked me to mark up thekeyword, regardless of the size anddo not change the keyword of the search source`, and see it. Please accept it.

Purpose

Suppose that data contains the text of the search source. On the other hand, the purpose of this time is to return the character string as if it was marked up regardless of the size when searching with keyword.

result

1. Judge the keyword before(? I)regardless of size (i stands for incentive)
2. Enclose the keyword in()to make one group
3. Add the part to be changed + $ 1 (By the way, if there are two groups, $ 1 $ 2)

↓ ↓ It looks like this when written in code ↓ ↓

String keyword = "java";
String data = "Java java javaJava";

// (?i)Is not case sensitive
//Hit characters()Group by
data = data.replaceAll("((?i)" + Pattern.quote(keyword) + ")", "<mark>$1</mark>");

// <mark>Java</mark> <mark>java</mark> <mark>java</mark><mark>Java</mark>
System.out.println(data);

Gist

To the result

I was told that it would be awkward if I did it with a gorigori. .. .. Lol (I was wondering if it was while)

Bad example

Pattern p = Pattern.compile(keyword, Pattern.CASE_INSENSITIVE).matcher(data);
while(p.find()) {
  int start = p.start();
  int end   = p.end();
  ~Calculate from the found location information and fill in the gorigori tag~
}

Impressions

I think I was able to implement it quite neatly and completely. I want to search for anything and mark up and display the results! How to write that is perfect for processing. This is just an example, so please use it as a reference.

Reference site

http://a4dosanddos.hatenablog.com/entry/2016/04/06/002657