[FIXED] Replace every second occurency of a substring, Java

Issue

Trying to replace every second occurence of "Object-oriented programming" substring in a given string "text". I am a beginner in Java and the aim of the task is to use only String class methods. Below is what I came up with so far. Thanks in advance for any help)

public class ExerciseString {
    public static void main(String[] args) {
        String s = "Object-oriented programming is a programming language model organized around objects rather than \"actions\" and data rather than logic. Object-oriented programming blabla. Object-oriented programming bla.";
        changeToOOP(s);
    }

    static void changeToOOP (String text) {
        String str = "Object-oriented programming"; // добавить игнорирование регистра
        String str2 = "OOP";

        int index = 0;
        int count = 0;

        while (true) {
            index = text.indexOf(str, index);

            if (index != -1) {
                count++;
                index += str.length();

                if (count % 2 == 0){
                    text = text.replace(text.substring(index - str.length(), index), str2);
                }

            }  else {
                break;
            }
        }

        System.out.println(text);
    }
}

Solution

String::replace replaces every occurrence and therefore its use for your requirement is not right. You can use

text = text.substring(0, index) + str2 + text.substring(index + str.length());

Note that 0 % 2==0; therefore, if you want to replace the occurrence number second, fourth, sixth and so on, use count % 2 != 0 in the inner if block. Also, increment index and count after processing the previous index and count values i.e. move the following after the inner if block:

count++;
index += str.length();

Demo:

public class ExerciseString {
    public static void main(String[] args) {
        String s = "Object-oriented programming is a programming language model organized around objects rather than \"actions\" and data rather than logic. Object-oriented programming blabla. Object-oriented programming bla.";
        changeToOOP(s);
    }

    static void changeToOOP(String text) {
        String str = "Object-oriented programming"; // добавить игнорирование регистра
        String str2 = "OOP";

        int index = 0;
        int count = 0;

        while (true) {
            index = text.indexOf(str, index);
            if (index != -1) {
                if (count % 2 != 0) {
                    text = text.substring(0, index) + str2 + text.substring(index + str.length());
                }
                count++;
                index += str.length();
            } else {
                break;
            }
        }

        System.out.println(text);
    }
}

Output:

Object-oriented programming is a programming language model organized around objects rather than "actions" and data rather than logic. OOP blabla. Object-oriented programming bla.

Answered By - Arvind Kumar Avinash
Answer Checked By - Senaida (JavaFixing Volunteer)