方法一

private static int getNumLenght(long num){

        num = num>0?num:-num;

        return String.valueOf(num).length();

    }

方法二

private static int getNumLenght(long num){

        num = num>0?num:-num;

        if (num==0) {

            return 1;

        }

        return (int) Math.log10(num)+1;

    }

方法三

private static int getNumLenght(long num){

        if (num==0) {

            return 1;

        }

        int lenght = 0;

        for (long temp = num ; temp != 0; temp/=10){

            lenght++;

        }

        return lenght;

    }