410遞迴字串替換

/******
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, c1, c2; 
        System.out.print("Input a string: ");
        s = keyboard.nextLine();
        System.out.print("Input a character: ");
        c1 = keyboard.nextLine();
        System.out.print("Input another character: ");
        c2 = keyboard.nextLine();
        System.out.printf("%s\n", replace(s, c1, c2));
    }
    public static String replace(String a,String b,String c)
    {
        if(a.equals(""))
            return a;
        else if(a.substring(0,1).equals(b))
            return c+replace(a.substring(1),b,c);
        else
            return a.substring(0,1)+replace(a.substring(1),b,c);
    }
}