The difference between static class and non static class.

A static class is a class that is inside a class and defines a static modifier. And where does the static class function? It can be understood in the structure of a struct in C, followed by 2 concepts: inner class and Static modifier statics.
A, first, the inner class is used because the inner class has a certain relationship with the outer class, and often only the outer class calls this inner class. Therefore, it is not necessary to use a Java file specifically to store this class.

B, Static is used to modify the internal members of the class. such as static methods, static member variables. Its only function is to be generated as the class is loaded (not as the object is produced), so that it can be obtained directly with the class name + static member name. This allows the static inner class to be understood, and it can be obtained directly from the external class name + internal class name.

The difference between static class and non static class.