public Boolean hasRepeatedNumber(String inputNumber) {
        boolean isRepeated = false;  //0表示不重复

        for(int i=0; i<3; i++) {
            for(int j=i+1; j<4; j++) {
                if(inputNumber.charAt(i) == inputNumber.charAt(j)){
                    isRepeated = true;
                }
            }
        }
        return isRepeated;
    }