Append underscore before each capital letter in string

Append underscore before each capital letter in the string

We can append any character(like underscore, special characters) before each capital letter in a given string using methods available in Character class, StringBuffer, and StringBuilder.

Example:

Input:      KeeplearnersBlogspotCom

Output: _Keeplearners_Blogspot_Com

Program:

public class appendCharacter {
    public static void main(String[] args) {
    String str = "KeeplearnersBlogspotCom";
    String newStr = "";

    for (int i = 0; i <= str.length() - 1; i++) {
        if (Character.isUpperCase(str.charAt(i))) {
            newStr += "_" + str.charAt(i);
            //newStr+=str.charAt(i);
    }   else {
            newStr += str.charAt(i);
        }
    }
    System.out.println("append underscore before each capital letter");
    System.out.println(newStr);

    StringBuffer sb = new StringBuffer();

    for (int i = 0; i <= str.length() - 1; i++) {
        if (str.charAt(i) >= 'A' && str.charAt(i) <= 'Z') { // 'A' <= 'ch' <='Z'
            sb.append("_");
            sb.append(str.charAt(i));
        } else {
            sb.append(str.charAt(i));
        }
    }
    System.out.println("append underscore before each capital letter using stringbuffer");
    System.out.println(sb);

    StringBuilder sbu = new StringBuilder();

    for (int i = 0; i <= str.length() - 1; i++) {
        if ('A' <= str.charAt(i) && str.charAt(i) <= 'Z') {
            sbu.append("_");
            sbu.append(str.charAt(i));
        } else {
            sbu.append(str.charAt(i));
        }
    }
    System.out.println("append underscore before each capital letter using stringbuilder");
    System.out.println(sbu);
    }
}

Output:
Append underscore before each capital letter in string

Please comment below to feedback or ask questions.