407尾端遞迴計算總和

/******
檔名：JPA04.java
題目：TQC+ JAVA6物件導向程式設計 參考答案
時間：2015/06
作者：fang shi mai
******/
import java.util.Scanner;

public class JPA04
{
    static Scanner keyboard = new Scanner(System.in);
    
    public static void main(String args[])
    {
        String s; 
        System.out.print("Input a string of numbers: ");
        s = keyboard.nextLine();
        System.out.printf("尾端遞迴：%d\n", sumTail(s, 0));
        System.out.printf("迴圈：%d\n", sumLoop(s, 0));
        System.out.print("Input a string of numbers: ");
        s = keyboard.nextLine();
        System.out.printf("尾端遞迴：%d\n", sumTail(s, 0));
        System.out.printf("迴圈：%d\n", sumLoop(s, 0));
    }
    public static int sumTail(String a,int b)
    {
        if(a.equals(""))
            return b;
        return sumTail(a.substring(1),b+Integer.parseInt(a.substring(0,1)));
    }
    public static int sumLoop(String a,int b)
    {
        while(!a.equals(""))
        {
            b=b+Integer.parseInt(a.substring(0,1));
            a=a.substring(1);
        }
        return b;
    }
}