Update specific object items in array list Java

I want to ask a question, how do I update the records in the array list object:

For example:

List<User> userList = new ArrayList<User>();

User user = new User();
user.setUserId(1);
user.setUsername("user1");
userList.add(user);

User user = new User();
user.setUserId(2);
user.setUsername("user2");
userList.add(user);

User user = new User();
user.setUserId(3);
user.setUsername("user3");
userList.add(user);

Now I want to update a specific record in my array list. Suppose I want to update the user name of the user ID #2, for example:

User user = new User();
user.setUserId(2);
user.setUsername("new_username2");

//before i want to remove or update the record on the list which contain user id #2
userList.add(user);

Like I want to search userlist from the list Contains (2) then delete or update it with the new value

Thank you in advance

Solution

In your case, I think it's better to use map instead of list:

Map<Integer,User> userMap = new HashMap<Integer,User>();

User user = new User();
user.setUserId(1);
user.setUsername("user1");
userMap.put(user.getUserId(),user);

user = new User();
user.setUserId(2);
user.setUsername("user2");
userMap.put(user.getUserId(),user);

user = new User();
user.setUserId(3);
user.setUsername("user3");
userMap.put(user.getUserId(),user);

In this way, you can directly search for the required userid:

User userToModify = userMap.remove(idToModify);
userToModify.setUsername("new name");
userToModify.setUserId(54);
userMap.put(user.getUserId(),userToModify);

If you only need to find objects through one field (userid in this case), the map is more efficient and easy to use (and maintainable)