Type []? arrayName

Type? array name[]；

Example:

int[]？ myList

int？ my list[]； [0]. These two definitions usually recommend the first format, because arrays (such as int[]) are also a reference data type, so the first format is not only more semantic, but also more readable.

[1]. Only one data type can be stored in an array, but not multiple data types in the village;

[2]. When defining array values, only one reference variable is defined. This reference variable not only needs any effective memory, so this array cannot be used, and it must be initialized before it can be used.

[3]. When defining an array, you cannot specify the length of the array.