406遞迴字串計算

/******
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: ");
        s=keyboard.next();
        System.out.printf("%s has %d As\n",s,countA(s));
        
        System.out.print("Input a string: ");
        s=keyboard.next();
        System.out.printf("%s has %d As\n",s,countA(s));
    }
    public static int countA(String str)
    {
        if(str.equals(""))
            return 0;
        else if(str.substring(0,1).equals("A"))
            return 1+countA(str.substring(1));
        else
            return countA(str.substring(1));
    }
}