Question

I have a ArrayList of Clients, can someone please tell me how to write a loop and get each client in the arraylist

List<Client> Clients = new ArrayList<Client>();

Answer 1

There are a number of ways to implement looping through an ArrayList. The three most common ways used are:

Case 1: The conventional for loop

for(int i=0; i<clients.size; i++){
    clients.get(i).doSomeMethod(); //Code to work with individual client here
}

Use when the index of an element is required. Also useful when you wish to iterate through multiple collections. Can be used to modify the current index element or any element you know the index of. All in all allows the programmer much more control then the methods listed below.

Case 2: The ‘enhanced’ for loop – otherwise known as the ‘for-each’ loop

for(Client client: Clients) {
  client.doSomeMethod(); //Code to work with a client here    
}

Enhanced for loops can’t be used for everything; for example they cannot be used to remove elements as you traverse the Collection (the ArrayList in this case), they are also not useful if you are trying to cycle through multiple collections. They’re most useful when you want to go through your ArrayList in first-to-last order and the index of the current element is not required.

Case 3: The iterator approach:

Iterator<Client> itr = clients.iterator(); 
while(itr.hasNext()) {
    Client myClient = itr.next(); 
    myClient.doSomeMethod()//Code to work with myClient here
} 

This approach is practically what the enhanced for loop is doing underneath and was added for completeness.