Reversing each alphabet of the words, Keeping the order of the words and whitespaces intact

InPlaceRev.java

import java.util.Scanner;
class InPlaceRev{
	public static void main(String args[]){
		Scanner sc = new Scanner(System.in);
		String str = sc.nextLine();
		StringBuilder sbAns = new StringBuilder();

		int i = 0;
		while(i < str.length()){
			StringBuilder sbRev = new StringBuilder();

			while(i < str.length() && Character.isLetter(str.charAt(i))){
				sbRev.append(str.charAt(i));
				i++;
			}
			sbAns.append(sbRev.reverse());

			while(i < str.length()){
				sbAns.append(str.charAt(i));
				i++;
			}
		}
		
		System.out.println(sbAns);
		
	}
}

"This is SaM!" changes to "sihT is SaM!"