Test.java

public class EndpointA {
  private UserService userService;
  private AService aService;
  /*constructor */
  public EndpointA(UserService userService,AService aService){
    this.userService = userService;
    this.aService= aService;
  }
}

public class EndpointB {
  private UserService userService;
  /*constructor */
  public EndpointB(UserService userService){
    this.userService = userService;
  }
}

public class UserServiceImpl implements UserService {
  private static final _INSTANCE = new UserServiceImpl();
  public static UserService getInstance(){
    return _INSTANCE;
  }
  private UserServiceImpl(){}
}

public class AServiceImpl implements AService {
  private static final _INSTANCE = new AServiceImpl();
  public static AService getInstance(){
    return _INSTANCE;
  }
  private AServiceImpl(){}
}


public class EndpointFactory{
  public EndpointA createEndpointA(){
    return new EndpointA(UserService.getInstance(),AService.getInstance());
  }
  
   public EndpointB createEndpointB(){
    return new EndpointB(UserService.getInstance());
  }
  
}
public class Test{
  @Test
  public void init(){
    EndpointFactory endpointFactory = new EndpointFactory();
    EndpointA endpointA = endpointFactory.createEndpointA();
    EndpointB endpointb = endpointFactory.createEndpointB();
    
  }
}