[AppA] Use star imports

package appA;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.net.ServerSocket;

import java.net.Socket;

import java.util.ArrayList;

import java.util.Iterator;

import java.util.List;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.io.*;

import java.net.*;

import java.util.*;

import java.util.concurrent.*;

public class MusicServer {

  final List<ObjectOutputStream> clientOutputStreams = new ArrayList<>();