Some embodiment of polymorphism in Java, rewriting and wrapper classes

1. Heterogeneous arrays

Polymorphism of the expression and double can directly convert int a=3;double to accept int b=a;
Animal dog=new Dog ();//Instantiate a Dog object modification before notice upward conversion
Down conversion//type Restore
instanceof determines the type of the attribute, which can be used to avoid type conversion exceptions.
D instanceof Dog, judging if D is not a dog type, if it is complete forced conversion of dog d= (dog) dog;

Different subclasses belonging to the same parent class:

Animal is the parent class of dog Cut

Animal dog=new Dog ();//Use a reference to the parent class to point to the instantiation of the child class.
Cut cut =new cut ();
Animal [] animal=new animal[2];
Animal[0]=dog;
Animal[1]=cut;

2. Rewrite

Overriding note that during the rewrite process, the access modifier can be enlarged, and the return value can be reduced;

Parent class Method:
Public Animal Lingyang (Animal d) {
return D;
}
Subclass Overrides:

Public Dog Lingyang (Animal d) {
Dog dong = (dog) D;
return dog;
}

3.8 Basic data types corresponding to the wrapper class
int-->integer;

double-->double;

float-->float;

byte-->byte;

boolean-->boolean;

short-->short;

long-->long;

char-->character;

int b=1;
Integer c=b;---------->//the process of converting a basic data type to a wrapper class is called boxing

Integer b=1;
int c=b;-----> unpacking;

The above are all small knowledge, * * *

Some embodiment of polymorphism in Java, rewriting and wrapper classes