What is the difference between set and list in Java?

In Java, Set and List are two different types of collection, with the main differences as follows:

1. Duplicate elements: Sets do not allow duplicate elements, each element in a Set is unique; whereas Lists allow duplicate elements, there can be multiple identical elements.
2. Element order: Sets do not guarantee the order of elements, as elements are unordered in a set; whereas in a list, the order of elements is maintained and can be accessed according to the order in which they were inserted.
3. Storage method: Sets use data structures such as Hash Tables or Trees to store elements, while Lists use arrays or linked lists to store elements.
4. Interface features: The common implementations of the Set interface include HashSet, LinkedHashSet, and TreeSet, which allow for operations such as checking for element existence, adding elements, and removing elements. The common implementations of the List interface include ArrayList, LinkedList, and Vector, which provide operations such as accessing elements by index, adding elements, and removing elements.

In general, Set is suitable for scenarios where duplicate elements are not allowed and the order of elements does not matter, while List is suitable for scenarios where the order of elements needs to be maintained and duplicate elements can be included. Choosing the appropriate collection type based on specific needs can improve code efficiency and readability.