<EffectiveJava> Reading notes--01 The use of inheritance note

1, methods in the constructor method of the parent class cannot be called to override the quilt class.

Analysis:

When initializing a subclass, the parent class is initialized first, that is, the constructor method of the parent class is called;

If other methods that can be overridden are called in the constructor of the parent class, then the call is actually the overridden method in that subclass;

So the subclass is not initialized, so it can cause some problems.

The sample code is as follows:

Parent class:

 Public class Father1 {    public  Father1 () {        overRide1 ();    }      Public void OverRide1 () {        System.out.println ("Member method of the parent class ...)     ........................

Sub-class:

 Public classSon1extendsFather1 {Private FinalDate date;  PublicSon1 () {Date=NewDate (); } @Override Public voidOverRide1 () {System.out.println (date); }     Public Static voidMain (string[] args) {Son1 son1=NewSon1 ();    Son1.override1 (); }}

If you run the main method of the subclass, the result of the console output is:

Null
Mon APR 12:55:48 CST 2017

When the parent class is initialized, the OverRide1 method of the subclass is called in the constructor method;

<EffectiveJava> Reading notes--01 The use of inheritance note