How to retrive DELETE string from ROLE_DELETE_USER with reqular expression?
String role = "ROLE_DELETE_USER";
Pattern pattern = Pattern.compile("???");
Matcher matcher = pattern.matcher(role);
System.out.println(matcher.group());
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3 Answers
You could do
String delete = role.substring(role.indexOf("_") + 1, role.lastIndexOf("_"));
1 Comment
Kijewski
@Flavio, use regex only as a last resort. Reimeus' solution is far better than a regular expression for your particular problem.
Regular expressions are meant to handle patterns. You don't have much of a pattern (just one example), but this will work in at least that one case.
String role = "ROLE_DELETE_USER";
Pattern pattern = Pattern.compile("^ROLE_(.*)_USER$");
Matcher matcher = pattern.matcher(role);
if(matcher.find()) {
System.out.println(matcher.group(1));
}
Here, (.*) is a capture group. match.group(1) retrieves the content of the first capture group.
Of course, you could also just do
String role = "ROLE_DELETE_USER";
role = role.substring(5, role.length() - 5)
System.out.println(role);
3 Comments
Flavio
When I'm trying to run your code i've got
Exception in thread "main" java.lang.IllegalStateException: No match found.Flavio
Very well! But it works not properly when I'm typing something like that
ROLE_DE__LETE_USER (wrong expression).
Paul Draper
@Flavio, your question does not say what should happen in such a case. You've given exactly one example. If it should work in other cases, you may want to specify that in your question.
It doesn't help to have only one example of strings to parse, because you could do it in multiple ways. If you wanted to, here are a couple patterns:
[A-Z]+_(.*)_[A-Z]+
[A-Za-z]+_(.*)_[A-Za-z]+
Which would come out as:
String role = "ROLE_DELETE_USER";
Pattern pattern = Pattern.compile("[A-Z]+_(.*)_[A-Z]+");
Matcher matcher = pattern.matcher(role);
matcher.find();
System.out.println(matcher.group(1));
An alternative solution (not using regex) would to break down the roles into a string array:
String input = "ROLE_DELETE_USER";
String[] tasks = input.split("_");
//args[0] == "ROLE"
//args[1] == "DELETE"
//args[2] == "USER"
This allows a lot more flexibility imo for figuring out what you want to do with the input.
