Write code to check if a string is all Digit via char array
public class Main { public static void main(String[] argv) { String str = "book2s.com"; System.out.println(isDigit(str)); }//from ww w . ja va 2 s . co m public static boolean isDigit(String str) { if (isNotNull(str)) { for (char c : str.toCharArray()) { if ((c < '0' || c > '9')) return false; } } else { return false; } return true; } public static boolean isNotNull(String str) { if (null != str && !"".equals(str)) { return true; } else { return false; } } }