Consider the following code:

public interface Vocaloid $\{$

void applyFilter$($Filter f$)$;

void sing$()$;

void adlib$()$;

void callAndResponse$()$;

$\}$

public class HatsuneMiku implements Vocaloid $\{$

void applyFilter$($Filter f$)\{$

filter.apply$($this$)$;

$\}$

void sing$()\{$

$\}$

System.out.println$("$Hatsune Miku sings$")$;

String adlib$($int seed$)\{$

System.out.println$("$Hatsune Miku adlibs with seed $"+$ seed$)$;

$\}$

void callAndResponse$()\{$

System.out.println$("$Miku calls for a response"$)$;

$\}$

$\}$

Which method does need to implement in order to compile?

void adlib$()$

String toString$()$

boolean equals$()$

The class

compiles without any changes.