TQC+ JAVA

JPA04.java

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\r\n", replace(s, c1, c2));
    }
	public static String replace(String s, String c1, String c2) {
		if(s.equals("")) {
			return s;
		}
		if(s.substring(0, 1).equals(c1)) {
			return c2 + replace(s.substring(1), c1, c2);
		}
		return s.substring(0, 1) + replace(s.substring(1), c1, c2);
	}
}