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java

Which definitions of the MyInterface interface are correct?

java

What is the result of following code execution: class User { public Integer id; public String username; public User(Integer id, String username) { this.id = id; this.username = username; } } public static void main (String[] args) { List<User> userList = new ArrayList<>(); userList.add(new User(1, "admin")); userList.add(new User(2, "guest")); userList.add(new User(3, null)); Map<Integer, String> idsUsernamesMap = userList.stream().collect(Collectors.toMap(user -> user.id, user -> user.username)); idsUsernamesMap.forEach( (k,v) -> System.out.println("id: " + k + "; username: " + v)); }