Java8 Stream Conditional Handling - java-8

Question

I have a list of User objects.
public class User{
private String name;
private String role;
private String status;
}
I wanted to use stream API to perform two operations.
See if list has User name as "Admin" if not throw custom exception (e.g UserNotFoundException)
If User name "Admin" is available in the list then mark the status of that user as "Active" and status of rest all users as "InActive".
How can i perform above operations in a concise way.

Answer 1

The below snippet should do what you expect
List<User> userList = Arrays.asList(new User("Admin", null, "Draft"),
new User("User", null, "Draft"));
userList.stream()
.filter(u -> u.name.equals("Admin"))
.peek(v -> userList.forEach(u -> u.status = u.name.equals("Admin") ? "Active" : "Inactive"))
.findAny()
.orElseThrow(IllegalArgumentException::new);
userList.forEach(System.out::println);
In the peek function, I am streaming the userList once more to set the status. Even if we used a loop, to ensure correctness, we need to iterate twice. First to need to determine if Admin exist and again to set status.
Output:
User{name='Admin', status='Active'}
User{name='User', status='Inactive'}

Answer 2

You could do this in two steps, 1. filter wi admin and throw an exception if does not match
2. Update the status
users.stream()
.filter(user -> user.name.equals("Admin"))
.findAny().orElseThrow(UserNotFoundException::new).setStatus("Active");
users.stream()
.filter(user -> !user.name.equals("Admin"))
.forEach(user -> user.setStatus("Inactive"));