Java compressing Strings

Question

I need to create a method that receives a String and also returns a String.

Ex input: AAABBBBCC

Ex output: 3A4B2C

Well, this is quite embarrassing a

Answer 1

 // O(N) loop through entire character array
 // match current char with next one, if they matches count++
 // if don't then just append current char and counter value and then reset counter.
// special case is the last characters, for that just check if count value is > 0, if it's then append the counter value and the last char

 private String compress(String str) {
        char[] c = str.toCharArray();
        String newStr = "";
        int count = 1;
        for (int i = 0; i < c.length - 1; i++) {
            int j = i + 1;
            if (c[i] == c[j]) {
                count++;
            } else {
                newStr = newStr + c[i] + count;
                count = 1;
            }
        }

        // this is for the last strings...
        if (count > 0) {
            newStr = newStr + c[c.length - 1] + count;
        }

        return newStr;
    }