Java Several collection usage cases

The difference between Collection and collections.

Collections is a Java.util class that contains a variety of static methods related to collection operations.

Collection is a Java.util interface, which is the parent interface of various collection structures.

Does the List, Set, and map inherit from the collection interface? List,set is map is not

The difference between ArrayList and vectors. Normal work priority use ArrayList
I. Synchronization: vector is thread-safe, that is, synchronous, and ArrayList is a thread program is not secure, not synchronous
Two. Data growth: When growth is needed, vectors grow by default to the original, while ArrayList is half the original

The difference between HashMap and Hashtable. Normal work priority use HashMap
I. Historical reasons: Hashtable is based on the old dictionary class, HashMap is an implementation of the map interface introduced by Java 1.2

Two. Synchronization: Hashtable is thread-safe, that is, synchronous, and HashMap is a thread program is not secure, not synchronous

Three. Value: Only HashMap can let you use NULL as the key or value of an entry for a table

Java Several collection usage cases