public class StrToNum { public static void main (String[] args){ String input = "123"; double num = 0; int val ; int length = input.length(); for(int i=0 ;i< length ; i++){ val = input.charAt(i); // ASCI value of char '1' is 49 val = val - 48; num = num + val * Math.pow(10, (length-1)-i); } System.out.println("Value::"+ num); } }