fill the code sample, without any errors

Container.java code

package Lab$7$;

import java.util.$*$;

import java.io$.*$;

$/**$

$*$ This class is a container that holds an unlimited number of

$*$ String objects. It is able to remove objects and add objects.

$*/$

public class Container $\{$

$//$ No instance variable should be defined for this class.

$/**$

$*$ Reads the given file and add it into a list.

$*$ Each element of the list contains one line of the file.

$*$ @param fileName is the name of the file that is read in this method.

$*/$

public static final List readFile$($String fileName$)\{$

$//$ add your code here. You may change the return value.

return null;

$\}$

$/**$

$*$ This method adds the obj to the container.

$*$ @param obj is the object that is added to the container.

$*/$

void add$($Object object$)\{$

$//$ insert your code here

$\}$

$/**$

$*$ This method removes the object from the container

$*$ @return returns the removed object.

$*/$

Object remove$()\{$

$//$ insert your code here, you may want to change the return value

return null;

$\}$

$/**$

$*$ @return It returns the number of elements in the container.

$*/$

int getSize$()\{$

$//$ insert your code here. You may want to change the return value.

return $0$;

$\}$

$\}$

$/**$

$*$

$*$ This class simulates a Queue, which is a data structure that insert and remove data

$*$ by FIFO $($first$-$in$,$ first$-$out$)$ rule

$*$

$*/$

class Queue extends Container$\{$

ArrayList queue;

$/**$

$*$ This is the constructor that initializes the queue

$*$ with all the strings in the fileName that is labeled

$*$ by "Queue"

$*$ @param fileName is the name of the file that is read.

$*/$

public Queue$($String fileName$)\{$

$//$ insert your code here

$\}$

$/**$

$*$ This method adds the object into the Queue.

$*$ Please note that the rule of the queue insertion$/$removal is

$*$ First in$,$ First out.

$*$ @param obj is the object that is added to the queue.

$*/$

@Override

public void add$($Object obj$)\{$

$//$ insert your code here

$\}$

$/**$

$*$ This method removes an object from the Queue.

$*$ Please note that the rule of the queue insertion$/$removal is

$*$ First in$,$ First out.

$*/$

@Override

public Object remove$()\{$

$//$ insert your code here. You may want to change the return value.

return null;

$\}$

$/**$

$*$ @return returns the object which is in front of the queue.

$*/$

public Object top$()\{$

$//$ insert your code here. You may want to change the return value.

return null;

$\}$

$/**$

$*$ Returns the number of items in the queue.

$*/$

@Override

public int getSize$()\{$

$//$ insert your code here. You may want to change the return value.

return $0$;

$\}$

$\}$

$/**$

$*$

$*$ This class simulates a Stack, which is a data structure that insert and remove data

$*$ by FILO $($first$-$in$,$ last$-$out$)$ rule

$*$

$*/$

class Stack extends Container$\{$

ArrayList stack;

$/**$

$*$ This is the constructor that initializes the stack

$*$ with all the strings in the fileName that is labeled

$*$ by "Stack"

$*$ @param fileName is the name of the file that is read.

$*/$

public Stack$($String fileName$)\{$

$//$ insert your code here.

$\}$

$/**$

$*$ This method removes an object from the stack.

$*$ Please note that the rule of the stack insertion$/$removal is

$*$ First in$,$ Last out.

$*/$

@Override

public void add$($Object obj$)\{$

$//$ insert your code here.

$\}$

$/**$

$*$ This method removes an object from the stack.

$*$ Please note that the rule of the stack insertion$/$removal is

$*$ First in$,$ Last out.

$*/$

@Override

public Object remove$()\{$

$//$ insert your code here. You may want to change the return value.

return null;

$\}$

$/**$

$*$ @return returns the object which is on top of the stack.

$*/$

public Object top$()\{$

$//$ insert your code here. You may want to change the return value.

return null;

$\}$

$/**$

$*$ Returns the number of items in the stack.

$*/$

@Override

public int getSize$()\{$

$//$ insert your code here. You may want to change the return value.

return $0$;

$\}$

$\}$

ContainerTester.java code

package Lab$7$;

import static org.junit.jupiter.api.Assertions.$*$;

import org.junit.jupiter.api.AfterAll;

import org.junit.jupiter.api.AfterEach;

import org.junit.jupiter.api.BeforeAll;

import org.junit.jupiter.api.BeforeEach;

import org.junit.jupiter.api.Test;

class ContainerTester $\{$

@Test

void testQueue$1()\{$

Container container $=$ new Queue$("$input$.$txt$")$;

int expected $=10$;

int actual $=$ container.getSize$()$;

assertEquals$($expected$,$ actual, "The queue is not populated properly or getSize$()$ method is not correct"$)$;

$\}$

@Test

void testQueue$2()\{$

Container container $=$ new Queue$("$in$.$txt$")$;

int expected $=0$;

int actual $=$ container.getSize$()$;

assertEquals$($expected$,$ actual, "The queue is not populated properly or getSize$()$ method is not correct"$)$;

$\}$

@Test

void testQueueAdd$1()\{$

Container container $=$ new Queue$("$in$.$txt$")$;

container.add$("$Jack$")$;

int expected $=$