Extracting placeholders from string

Extracting placeholders from string

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I got 2 strings. One contains the "format" and placeholders, while the other contains the actual value for the placeholders.

For example:

String one: "<username> <password>"

String two: "myUser myPass"

String one: "<name>, <familyName>"

String two: "John, Smith"

I'm trying to assign the variable String username the value of the username placeholder in the second string, and the variable String password the value of the password placeholder in the second string.

I know about the String.replaceAll() method, but wouldn't that just replace the first string by the second?

One potentially viable way to approach this would be to maintain a map of tokens and their replacements. Then, you may iterate that map and apply the replacements to your text, something like this:

String text = "There is a user <username> who has a password <password>";
Map<String, String> tokens = new HashMap<>();
tokens.put("<username>", "myUser");
tokens.put("<password>", "myPass");

for (Map.Entry<String, String> entry : tokens.entrySet()) {
    text = text.replaceAll(entry.getKey(), entry.getValue());


There is a user myUser who has a password myPass


Extracting placeholders from string [duplicate], Extracting placeholders from string [duplicate]. Posted by: admin October 23, 2018 Leave a comment. Questions: This question already has an answer here:. Here's utility class that is capable of filling strings with placeholders and extract values of placeholders from filled strings. Placeholders are enclosed in % characters or curly braces. Each placeholder has a pattern, which matches any value, that this placeholder can hold. It's functionality

This solves an ordinary String::replaceAll method:

String one ="<username> <password>";
String two = "<name>, <familyName>";

String username = "myUser";
String password = "myPass";
String name = "John";
String familyName = "Smith";

// will result in "myUser myPass" without the quotation marks
String outputOne = one.replaceAll("<username>", username).replaceAll("<password>", password);

// will result in "John Smith" without the quotation marks
String outputTwo = two.replaceAll("<name>", name).replaceAll("<familyName>", familyName);

StringTake—Wolfram Language Documentation, An expression placeholder for string interpolation may optionally contain a format valid for sprintf. This function will extract such or default to "s" the format for  The placeholders used by String.Format are zero based which means the first argument always corresponds to the {0} placeholder. This becomes difficult when you want to "nest" variables with placeholders like we did above. A much better solution would be to name our placeholders.

I would suggest to go ahead and use regex for this. First capture all keys keys from String 1 and create corresponding regex from which take values from String 2

Code to extract keys and corresponding values:

    String keyString = "<name>, <familyName>";
    int i  = 0;
    List<String> keys = new ArrayList<>();
    Pattern pattern = Pattern.compile("<(\\w+)>");
    Matcher matcher = pattern.matcher(keyString);
    StringBuilder sb = new StringBuilder("");
    while(matcher.find()) {
            String token = matcher.group(1);
        sb.append(keyString.substring(i, matcher.start()));
        sb.append("([\\w ]+)");
        i = matcher.end();

    Pattern valuePattern = Pattern.compile(sb.toString());
    Matcher valueMatcher = valuePattern.matcher("John, Smith");
    Map<String,String> keyValueMap = new HashMap<>();
    while(valueMatcher.find()) {
        int counter = 0;
        for(String key:keys) {
            keyValueMap.put(key, valueMatcher.group(++counter));

Similary execute for all other key value pairs.

Final JShell Output:

jshell> keyValueMap
keyValueMap ==> {password=myPass, familyName=Smith, name=John, username=myUser}

extract_formats: Extract String Interpolation Formats from Matched , string. Returns a string produced according to the formatting string format . The order of the placeholders in the format string does not match the order of the arguments in the code. We would like to leave Extract text from JSON response If, on the other hand, you wanted to replace the placeholders using some rules (e.g. using a Dictionary<string, string>), then you could do: Regex.Replace(text, pattern, m => substitutions[m.Groups[1].Value]);

sprintf - Manual, There are expected l10n errors in calendar-extract.properties due to double The solution would be to change the strings to not use the real placeholders  The placeholder names are delimited by underscores. So, first I need to extract a list of placeholder names. Then present to the user the name so the user can provide the value. Then, replace the placeholder name, including delimiters, with the values. I would like to have a pattern/solution that works with any number of placeholders.

1154448, get() : for use with literal strings, also acts as marker for the string extraction text considering a special comment for translators and replaces placeholders ( {0}  Placeholders are filled from right to left unless there is an exclamation point (!) in the format string. Forces lowercase. The formatted string displays all characters in lowercase format.

I18n ("The Adobe AEM Quickstart and Web Application."), Django then provides utilities to extract the translation strings into a message file. placeholders, specified with Python's standard named-string interpolation  The tutorial shows how to extract number from various text strings in Excel by using formulas and the Extract tool. When it comes to extracting part of a text string of a given length, Excel provides three Substring functions (Left, Right and Mid) to quickly handle the task.