stringReverse.java

//time complexcity O(n)  where n is the length of the string

public class stringReverse {

    public static void  printRev( String str, int idx ){

        if(idx==0){
            System.out.println(str.charAt(idx));
            return;
        }

        System.out.print(str.charAt(idx));
        printRev(str, idx-1);

    } 

    public static void main(String args[]){
        String str="abcd";
        printRev(str,str.length()-1);

    }
    
}