Replace Occurances of the given string

package strings;

/*

Given a string str that may contain one more occurrences of “AB”. 

Replace all occurrences of “AB” with “C” in str.

This should be in the same array. 

Solution should be optimized

Dont try to shift entire elements or something.

Examples:

Input  : str = "helloABworld"

Output : str = "helloCworld"

Input  : str = "fghABsdfABysu"

Output : str = "fghCsdfCysu"

*/

public class ReplaceOccurances {

    static char[] replace(char[] str) {

        int len = str.length;

        if (len < 2)

            return str;

        int i = 0; // Index in modified string

        int j = 0; // Index in original string

        // Traverse string

        while (j < len - 1) {

            // Replace occurrence of "AB" with "C"

            if (str[j] == 'A' && str[j + 1] == 'B') {

                // Increment j by 2

                j = j + 2;

                str[i++] = 'C';

                continue;

            }

            str[i++] = str[j++];

        }

        if (j == len - 1)

            str[i++] = str[j];

        // add a null character to terminate string

        str[i] = '\0';

        return str;

    }

    public static void main(String[] args) {

        String str = "helloABworldABGfG";

        System.out.println(replace(str.toCharArray()));

    }

}

/*

An efficient solution is to keep track of two indexes, one for modified string (i in below code) 

and other for original string (j in below code). If we find “AB” at current index j, 

we increment j by 2 and i by 1. Otherwise we increment both and copy character from j to i.

Below is implementation of above idea.

*/