I wasn't aware that any theoretical computer scientists felt that the Java collections had something wrong with them. What you may be running into is the idea that they're not good for teaching the fundamentals of data structures. In most universities, the computer science curriculum has a Data Structures class as one of the early-level classes. In those classes, students often learn how to create linked lists, maps, graphs, queues, trees, and other data structures that in most cases already exist in the language's core libraries. Most of the assignments could be done trivially simply by using those libraries. However, the point of the classes is to understand what's going on "under the hood", so to speak, and creating your own implementations of those data structures is a good way to gain a fundamental understanding of core computer science concepts. This doesn't mean, of course, that there's anything wrong with the built-in collections. In most cases, they'll be faster and more optimized than anything a student will create. But learning how to create your own implementations is a tremendously valuable learning experience that will help you as a computer scientist for the rest of your career.