Reverse a string without using string function in java

package javaprgms;

public class ReverseString {

            public static void main(String[] args) {

                        String str="Hello world";

                        String revstring="";

                        for(int i=str.length()-1;i>=0;--i){

                                    revstring +=str.charAt(i);

                        }

                        System.out.println(revstring);

            }

}

Output:

dlrow olleH