Java class, assigning a variable a small detail, and the meaning of a static callout variable

In the Java class, the variables defined outside the method, if the definition is not assigned, then the method can not be assigned to it, or error, can only be placed in a method to assign its value. (Why do you want to find out later?)

The variable of the static dimension is called a static variable, and when the class is instantiated by the system once, the system will give the static variable a single piece of memory space, that is, the static variable is not dependent on the instance, can be modified by any instance of the class, use.

A counter that can be used as the number of instances of a class, because the variable is reinitialized not every time a new instance is created, regardless of the instance.

Java class, assigning a variable a small detail, and the meaning of a static callout variable