public static void main(String[] args) {String numStr = "123121";System.out.println(isNumeric(numStr));System.out.println(isNumber(numStr));}//正则表达式 : 完美public static boolean isNumber(String str){String reg = "^[0-9]+(.[0-9]+)?$";return str.matches(reg);}//ASCII码 ,不能判断小数点有几个 :1.1.1 也会返回truepublic static boolean isNumeric(String str){ for(int i=str.length();--i>=0;){ int chr=str.charAt(i); System.out.println(chr); if(chr<48 || chr>57) { if(chr != 46) return false; } } return true;}