Properties of static under multiple units

The static modified method does not have many features, because at this time, the method has no "late binding" nature, that is, the base class reference even point to the export class, the call to the static method or the base class.

If you want to invoke the static method of the exported class, you can only use the Export class's reference (that is, the downward transition).

In fact, Static is implicitly added to the constructor, which is why the derived class can use super () to call the constructor of the base class in the constructor.

Static and variables do not have multiple features, because they are not "late-bound", but "early-bound".

Conditions required for multiple units:

1, the existence of inheritance relations;

2, the export class can override the method of overriding the base class;

3. A reference to the base class points to the object of the exported class and invokes the overridden method.

Note: Variables and static modification methods do not have this property;

The final modified method cannot be overridden and therefore does not have more than one condition;

Private modified variables do not have multiple features, because overridden overrides are not allowed at all (at the same time, the private method has an implicit final modification);

All but static and final (private is a final) can be overridden by overrides;

Properties of static under multiple units