UpperCase.java

public class UpperCase {
    public static String touppercase(String str) {                                 //O(n)    -- Time Complixity
        StringBuilder sb = new StringBuilder("");

        char ch = Character.toUpperCase(str.charAt(0));
        sb.append(ch);

        for(int i = 1; i<str.length();i++) {
            if (str.charAt(i) == ' ' && i<str.length()-1) {
                sb.append(str.charAt(i));
                i++;
                sb.append(Character.toUpperCase(str.charAt(i)));
            }else {
                sb.append(str.charAt(i));
            }
        }
        return sb.toString();
    }
    public static String compres(String str) {                                 //O(n)   -- Time Complixity
        String newstr ="";

        for(int i =0;i<str.length();i++){
            Integer count =1;
            while (i<str.length()-1 && str.charAt(i) == str.charAt(i+1)) {
                count++;
                i++;
            }
            newstr += str.charAt(i);
            if (count>1) {
                newstr += count.toString();
            }
        }
        return newstr;
    }
    public static void main(String[] args) {
        // String str = "hi, i am utkarsh";
        // System.out.println(touppercase(str));
        String str = "aaabbcccdd";
        System.out.println(compres(str));
    }
}