A brief discussion on the differences between static variables, member variables and local variables

The difference between static variables and member variables:

A: Different ownership

Static variables: belong to classes, class variables

Member variables: belong to objects, object variables, Instance variables

B: Different memory locations

Static variables: Static area of ​​method area

Member variables: Heap memory

C: Different life cycles

Static variables: Static variables are loaded as the class is loaded, and disappear as the class disappears

Member variables: Member variables exist with the creation of the object, and disappear as the object Disappear and disappear

D: Call different

Static variables: can be called through the object name, or can be called through the class name

Member variables: can only be called through the object name

The difference between member variables and local variables:

A: Different locations in the class

Member variables: outside the methods in the class

Local variables: In the method definition or method declaration

B: Different locations in memory

Member variables: in heap memory

Local variables: in stack memory

C: Different life cycles

Member variables: exist with the creation of the object, and disappear with the disappearance of the object

Local variables: exist with the call of the method, and disappear with the invocation of the method The method disappears after the call is completed

D: Different initialization values

Member variables: have default initialization values

Local variables: no default initialization values, must be defined, assigned, and then can be used.

Note:

The local variable name can be the same as the member variable name. When used in a method, the proximity principle is adopted.

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