17.ChangeToUppercase

package com.company;

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class ChangeToUpperCase {
    public static void main(String[] args){
        Scanner s = new Scanner(System.in);

        String text = s.nextLine();

        Matcher m = Pattern.compile("(?<=<upcase>)[^<>]*(?=</upcase)").matcher(text);

        while (m.find()){
            text = text.replace(m.group(), m.group().toUpperCase()).replace("<upcase>", "").replace("</upcase>", "");
        }
        System.out.println(text);
    }
}