The main points of polymorphism in Java

Polymorphism has three-factor inheritance, method overrides, parent-class references to child-class objects

Polymorphism can be understood as two parts: one is compile, one is runtime

Compile-time: Define rules; Run time: implement this rule specifically.

Compile time: The parent class is coerced into a subclass without error; Runtime: First go to the parent class to find this method and then see if the subclass has not overridden this method if it does not call the parent class, otherwise call the subclass override method;

Compile time: Not the same thing (ex: forcing a cat into a dog) does not give an error; Runtime: Not the same thing (ex: forcing a cat into a dog) will give an error.

The main points of polymorphism in Java