I have a regex pattern that will have only one group. I need to find texts in the input strings that follows the pattern and replace ONLY the match group 1. For example I have the regex pattern and the string to be applied on as shown below. The replacement string is "<---->"
Pattern p = Pattern.compile("\\w*(lan)\\w+");
Matcher m = p.matcher("plan plans lander planitia");
The expected result is
plan p<--->s <--->der p<--->itia
I tried following approaches
String test = "plan plans lander planitia";
Pattern p = Pattern.compile("\\w*(lan)\\w+");
Matcher m = p.matcher(test);
String result = "";
while(m.find()){
result = test.replaceAll(m.group(1),"<--->");
}
System.out.print(result);
This gives result as
p<---> p<--->s <--->der p<--->itia
Another approach
String test = "plan plans lander planitia";
Pattern p = Pattern.compile("\\w*(lan)\\w+");
Matcher m = p.matcher(test);
String result = "";
while(m.find()){
result = test.replaceAll("\\w*(lan)\\w+","<--->");
}
System.out.print(result);
Result is
plan <---> <---> <--->
I have gone through this link. Here the part of the string before the match is always constant and is "foo" but in my case it varies. Also I have looked at this and this but I am unable to apply any on the solutions given to my present scenario.
Any help is appreciated
You need to use the following pattern with capturing groups:
(\w*)lan(\w+)
^-1-^ ^-2-^
and replace with $1<--->$2
See the regex demo
The point is that we use a capturing group around the parts that we want to keep and just match what we want to discard.
String str = "plan plans lander planitia";
System.out.println(str.replaceAll("(\\w*)lan(\\w+)", "$1<--->$2"));
// => plan p<--->s <--->der p<--->itia
If you need to be able to replace the Group 1 and keep the rest, you may use the replace callback method emulation with Matcher#appendReplacement:
String text = "plan plans lander planitia";
String pattern = "\\w*(lan)\\w+";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(text);
StringBuffer sb = new StringBuffer();
while (m.find()) {
m.appendReplacement(sb, m.group(0).replaceFirst(Pattern.quote(m.group(1)), "<--->"));
}
m.appendTail(sb); // append the rest of the contents
System.out.println(sb.toString());
// output => plan p<--->s <--->der p<--->itia
Here, since we process a match by match, we should only replace the Group 1 contents once with replaceFirst, and since we replace the substring as a literal, we should Pattern.quote it.