Question

Does dependency injection mean that you don’t ever need the ‘new’ keyword? Or is it reasonable to directly create simple leaf classes such as collections?

In the example below I inject the comparator, query and dao, but the SortedSet is directly instantiated:

public Iterable<Employee> getRecentHires() {     SortedSet<Employee> entries = new TreeSet<Employee>(comparator);     entries.addAll(employeeDao.findAll(query));     return entries; } 

Answer 1

Just because Dependency Injection is a useful pattern doesn’t mean that we use it for everything. Even when using DI, there will often be a need for new. Don’t delete new just yet.