java - How to use AbstractList -

I'm new to Java, just started it a while ago. I am trying to create chat messenger (client-server) and I need a data structure in which I can store an online user (a socket and a string that contains the username). Now I did a lot of research and thought that the AbstraList can help me, but I have to face a problem

  public class collection & lt; E & gt; Abstracts & lt; E & gt; {Private integer size; Private e [] list; Public collection () {size = 0; List = new E [50]; } @ Override public e-mail (int index) {return list [index]; } @ Override Public Boolean Aid (E element) {return false; } @ Override Public Int size () {return list.length; } Public static zero main (string [] args) {Collection < String & gt; Obj = new collection (); Obj.add (new string ("1")); Obj.add (new string ("5"); System.out.println ("size =" + obj.size ()); }}   
 This is my code and clearly I could not find a way around the add function ... I  
  list = new E Tried to use [50];   
 But this gives a normal initialization error. In short, I do not know how to initialize the inventory object. Now I have three questions:  
 
 Is the server Is my approach to making a list of all customers on?  
 What should I do with the add () function?  
 Why are there two times in the first row? Obviously this is a template, but will not you need it once? Obviously you need both places, so what's the first and what is the other for? (The tutorial that I have learned is not considered silent)    
 
 
 to add items A list you can make, you do not need to create your own list class  
  list & lt; String & gt; MyList = new Arsèchchi & lt; String & gt; (); MyList.add ("Peter"); MyList.add ("Susan");   
 Now if you want to make a list of all usernames and sockets, you can use the map. Something like this  
  Maps & lt; String, socket & gt; MyMap = New Hashmop & lt; String, socket & gt; (); MyMap.put ("Peter", Peterrskete); MyMap.put ("Susan", Sense Socket);   
 This will allow you to get a socket with the user names  
  socket pies = myMap.get ("Peter");   
 Or you can create your username and socket class instead  
  public class usernameNumberPoint {the name of the private string; Private socket socket; Public user namespace (string name, socket socket) {this.name = name; this. Socket = socket; } Public string getName () {return name; } Public Socket Socket () {Return Socket; }}   
 Then it can be added to the list  
  list & lt; UsernameSocketPair & gt; MyList = New Arrestist & lt; Username SocketPayer & gt; (); MyList.add (new user nameSocketPear ("Peter", Patrssocket));   
 Whether this is a good idea or not, it depends on the rest of your code and how it is structured.  
 The answers to the questions clearly:  
 
 It depends on the rest of your code and how it is structured.  
 Do not use the first [E] [object] [] and put it on E when you get the 'element' in this way you instantiate (such as object [] list = new object [20]; < In the class declaration, e is happening twice because you are extending the type of abstracts and you are doing parameters by your class. For example, you can do this.   
 The following:  
  Public class MyList AbstractList  {}   
 N How to apply a solid version of a table list, as you wanted  
  Public category MyList & lt; E & gt; Abstracts & lt; E & gt; {Private Item [ ] = New object [10]; Private int size = 0, public e-mill (int i) {if (i> = size) new index auto offbound exception ("duh!"); Return (e) list [i] ;} Public Boolean addition (EE) {if (size> gt; = list.length} {object [new] newList = new object [list.length + 10]; System.arraycopy (list, 0, newList, 0, list .length); List = newList;} list [size] = E; Size ++; True true;} public integer size () {return size;} public static zero main (string [] arg s) {list & lt; String & gt; L = New MyList & lt; String & gt; (); For (int i = 0; i & lt; 100; i ++) {l.add ("" + i); } System.out.println (l.size ()); }}