I have an input string like this
I want to go to {places} where {things} are happening.
The values for {places} and {things} are computed lazily (i.e. first i find out what all keys needs to be replaced and then compute the values for them, and then replace them in the original string).
I am able to find out all the keys and removing them using the below code.
public class Temp {
private static final Pattern betweenCurlyBracesMatcher = Pattern.compile("\\{(.*?)\\}");
public static void main(String args[]) {
System.out.println(resolve2("hello {world} from {here}"));
}
public static String resolve2(String input) {
Map<String, String> keyValueMap = new HashMap<>();
Matcher matcher = betweenCurlyBracesMatcher.matcher(input);
while (matcher.find()) {
String key = matcher.group(1);
if (!keyValueMap.containsKey(key)) {
keyValueMap.put(key, computeValueForKey(key));
}
}
for (Map.Entry<String, String> entry : keyValueMap.entrySet()) {
input = input.replace("{" + entry.getKey() + "}", entry.getValue()); // << ugly code here
}
return input;
}
private static String computeValueForKey(String key) {
return "new" + key;
}
}
but I am not happy with
input = input.replace("{" + entry.getKey() + "}", entry.getValue());
because it means whenever i change my regex i will have to update this logic. Is there a more elegant solution to this problem.
input hello {world} from {here}
output hello newworld from newhere
input I want to go to {places} where {things} are happening.
output I want to go to newplaces where newthings are happening.
You should make use of the Matcher#appendReplacement and Matcher#appendTail APIs here:
Map<String, String> keyValueMap = new HashMap<>();
keyValueMap.put("places", "to America");
keyValueMap.put("things", "events");
String input = "I want to go to {places} where {things} are happening.";
Pattern pattern = Pattern.compile("\\{(.*?)\\}");
Matcher matcher = pattern.matcher(input);
StringBuffer buffer = new StringBuffer();
while(matcher.find()) {
matcher.appendReplacement(buffer, keyValueMap.get(matcher.group(1)));
}
matcher.appendTail(buffer);
System.out.println(buffer.toString());
This prints:
I want to go to to America where events are happening.