在java字符串中的两个字符之间添加点

public class Main {
    public static void main(String[] args) {
        String str = "HelloWorld";
        String result = insertDot(str, 2, 5);
        System.out.println(result); // 输出：He.lloWorld
    }

    public static String insertDot(String str, int start, int end) {
        String firstPart = str.substring(0, start);
        String secondPart = str.substring(end);
        return firstPart + "." + secondPart;
    }
}