2022-07-21 study notes of group 4 self-cultivation class (every day)

final keyword    
         The final , The ultimate

     final A structure that can be modified ：

1. class  public final class

                 The final class , Ultimate class

1. attribute  private  final  String name

        final Modifier constants cannot be changed

         Constant naming rules ： All the letters of a word are capitalized , If it's multiple words , Divide... With underscores , You can't just declare no assignment

1. Method  private  final  void show

         Can't be rewritten

Method rewrite annotation

@Override

We suggest that the rewritten annotation be indicated at the rewritten of the method

Ancestors ：Object （ Top level parent class ）

If a class doesn't specify who its parent class is , Then its parent is Object

Object There are 11 A way ：

1. hashCode( )： Its return value is actually the memory address of the object when it runs

hash Algorithm ： General translation “ hash ”, Put any length of input , Through a hash algorithm, it is transformed into a fixed length output , Output results

Password encryption MD5 encryption

SHA family

1. equals( )： and == No difference , Than the address , In order for subclasses to override

Integer Inside , There's a buffer , hold byte The number in the range is cached

1. toString( )： Convert to string , When we use objects directly , Will call... By default toString Method , In order for subclasses to override
2. finalize( )： Garbage collection methods
3. Clone( )： clone , Must be realized

summary

        Not much , But we need to understand more