Java regex with replace

Question

I need to replace string with a variable inside {} using a regex

For example:

"Hi, there are {online@US-server} players in the US server" to "Hi, there are 12 players in the US server"

Inside the Strings variables inside {} can be more than 1

I need this code to allow users to modify messages. variable inside {} after @ like in the example 'US-server' are put in by users so there aren't list to check for variable. Variables could be as strange as possible ex: '{online@test-UK}' '{online@asdtest}'

public static String getReplaced(String d) {
    String result = d.split("\\{online@")[0];

    for (int i = 1; i < d.split("\\{online@").length; i++) {
        String dd = d.split("\\{online@")[i];

        Pattern p = Pattern.compile("(.*?)}(.*)");
        Matcher m = p.matcher(dd);

        if (m.lookingAt()) {
            int count = 12;

            result += count + m.group(2);
        } else {
            result += dd;
        }
    }

    return result;
}

@jhamon I tried a lot of things but I have no familiarity with those things... The last I tried was "{online@(.*?)}(.*)" — kratess
– kratess, Commented Feb 19, 2020 at 16:12
Please edit your question to include the code you've tried, even if you think it's wrong — OneCricketeer
– OneCricketeer, Commented Feb 19, 2020 at 16:12
@cricket_007 I added the code. I tried many times to do the thing so sorry for my bad code. — kratess
– kratess, Commented Feb 19, 2020 at 16:16

jhamon · Accepted Answer · 2020-02-19 17:14:15Z

1

With \\{online@(.+)\\}as the regex, use a matcher to get the first capturing group. That will give you the part after the @.

Regex means:

\\{: litteral character '{'
online@: the string online@
.+: at least one character (anyone)
(.+): capturing group
\\}: litteral character '}'

Then simply use String#replaceAll(String regex, String replacement) (doc here).

Example:

int myIntValue = 12;
String myString = "there are {online@US-server} players";
Pattern p = Pattern.compile("\\{online@(.+)\\}") ;
Matcher m = p.matcher(myString) ;

if (m.find()) { // true if the pattern is found anywhere in your string.
  System.out.println("Variable part is : " + m.group(1)); // group 1 is the capturing group
  System.out.println(myString.replaceAll("\\{online@.+\\}", String.valueOf(myIntValue)));
}

If you need to find more than one placeholder in a single string:

String myString = "there are {online@US-server} players ,and {online@whatever}";
Pattern p = Pattern.compile("\\{online@(.+)\\}") ;
Matcher m = p.matcher(myString) ;

while (m.find()) { // true if the pattern is found anywhere in your string.
  System.out.println("Variable part is : " + m.group(1)); // group 1 is the capturing group
  System.out.println(myString.replace("{online@"+m.group(1)+"}", String.valueOf(myIntValue)));
}

edited Feb 19, 2020 at 17:14

answered Feb 19, 2020 at 16:47

jhamon

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5 Comments

jhamon Over a year ago

It's the first sentence of my answer. You just need to convert the int to a String.

kratess Over a year ago

Okay your code work to change all {} to a int but now I must know what int. How many players are online in the server? i need to change all {} with players in the server name after @

kratess Over a year ago

I need to know what is between {server@ and } and with this do the replace

kratess Over a year ago

Your code worked. thanks a lot for your time. Your regex didn't work so I changed it with (.*?)

jhamon Over a year ago

Strange. I tryed it and it worked fine. Could it be that you allow empty value after the @?

slim · Accepted Answer · 2020-02-19 16:41:58Z

1

You don't need regex for this, and probably shouldn't use it, because using user input as a regex has some potential security risks.

public String replaceTag(String tag, String replacement, String template) {
   private final String decoratedTag = "{online@" + tag + "}";

   return template.replace(decoratedTag, replacement);
}

You can call this repeatedly:

private String template = getTemplateFromUser();
private String output = template.replace('US-server', usServerCount);
output = output.replace('asdtest', testValue);
return output;

... or you can be more sophisticated and loop through a set of tag/value pairs, for example from a Map<String, String>

Note that String.replace() just replaces character sequences dumbly, it's not a regular expression replace, which for this problem is a good thing.

answered Feb 19, 2020 at 16:41

slim

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2 Comments

kratess Over a year ago

I don't have a list of path with variables. Every user put what they want like 'US-server' or 'Test-server' and through another method, you get player counter in the server. So after @ there is the server's name

slim Over a year ago

@kratess then I think you need to go back to your question, and carefully rewrite it to explain the requirement.

Domimax · Accepted Answer · 2020-02-19 16:22:56Z

0

([^\s]+)online@[A-Za-z\-]([^\s]+)

seems to work.

answered Feb 19, 2020 at 16:22

Domimax

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1 Comment

RyanNerd Over a year ago

This may answer the question. However, code only answers are not as useful as answers that document the code or have an detailed explanation on why this code is the solution to the question.

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