// Program to test solutions to problem #2 on the cse143 midterm, spring 2011.
// Fill in your solution to replace, then compile and run the program.

import java.util.*;

public class Test2 {
    public static String replace(String s, char target, char replacement) {
        // fill in your solution here
        // you can also rename the parameters above
    }

    // this is the sample solution
    public static String replace2(String s, char target, char replacement) {
        if (s.length() == 0)
            return "";
        else {
            String rest = replace2(s.substring(1), target, replacement);
            if (s.charAt(0) == target)
                return replacement + rest;
            else
                return s.charAt(0) + rest;
        }
    }

    public static void main(String[] args) {
        test("to be or not to be", 'e', 'o');
        test("to be or not to be", 'o', '-');
        test("to be or not to be", 'm', '!');
        test("Mississippi", 'i', 'e');
        test("hah!", 'h', '*');
        test("Hah!", 'h', '*');
        test("g", 'g', 'h');
        test("g", 'h', 'g');
        test("", 'g', 'h');
        test("abaabbaaabbbaaaabbbb", 'a', '-');
        test("abaabbaaabbbaaaabbbb", 'b', '-');
        test("aaa", 'a', '-');
        test("aaa", 'x', '-');
    }

    public static void test(String s, char target, char replacement) {
        System.out.println("testing replace(\"" + s + "\", '" + target + 
                           "', '" + replacement + "')");
        String result1 = replace2(s, target, replacement);
        boolean fail = false;
        try {
            String result2 = replace(s, target, replacement);
            if (!result1.equals(result2)) {
                fail = true;
                System.out.println("result should be \"" + result1 +
                                   "\", yours = \"" + result2 + "\"");
            }
        } catch (RuntimeException e) {
            System.out.println("threw " + e);
            fail = true;
        }
        if (!fail) {
            System.out.println("passed");
        } else {
            System.out.println("failed");
        }
        System.out.println();
    }
}