第一章课后习题1.3

1.3 只使用处理I/O的printDigit方法，编写一种方法以输出任意double型量（可以是负值）。

package com.algorithm.chapterone;

/**
 * 只使用处理I/O的printDigit方法，编写一种方法以输出任意double型量（可以是负值）
 * @author Gao·Rongzheng
 *
 */
public class QuestionThree {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        double num = -12.63;
        if (num < 0) {
            System.out.print("-");
            num = Math.abs(num);
        }
        int integer = (int) num;
        int integerLength = Integer.toString(integer).length();
        int decimalLength = Double.toString(num).length() - integerLength - 1;
        
        printDigit(num, -integerLength, decimalLength);
    }
    
    public static void printDigit(double num, int integerLength, int decimalLength) {
        //※ 递归方法的的基准
        if (integerLength == decimalLength) { return; }
        //※ 往基准靠拢
        integerLength++;
        int n = (int) (num * Math.pow(10, integerLength));
        System.out.print(n % 10);
        //※ 判断输出小数
        if (integerLength == 0) {
            System.out.print(".");
        }
        printDigit(num, integerLength, decimalLength);
    }
}