把一个字符串AaaBbbcccc变成AaaBbbCcc，写一个通用的函数

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;
public class test10 {

	public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);
      String str = sc.next();
      exChange(str);

	}
	public static String exChange(String str) {
		
		List<String> temp = Arrays.asList(str.split(""));
		List<String> list = new ArrayList<>(temp);
		String s = list.get(6).toUpperCase();
		list.set(6, s);
		list.remove(list.get(list.size()-1));
		String tempStr = list.stream().map(integer -> integer.toString()).collect(Collectors.joining(""));
		System.out.println(tempStr.toString());
		return tempStr;
	}
}