如果constructor里調(diào)用了一個(gè)成員方法，這個(gè)方法被子類override了，當(dāng)初始化一個(gè)子類實(shí)例時(shí)，父類的構(gòu)造函數(shù)被的調(diào)用，此時(shí)父類構(gòu)造函數(shù)的上下文里調(diào)用的成員方法，是父類的實(shí)現(xiàn)還是子類的實(shí)現(xiàn)？
你能不用運(yùn)行代碼，就能準(zhǔn)確說(shuō)出這些語(yǔ)句會(huì)打印什么出來(lái)呢？

創(chuàng)新互聯(lián)從2013年創(chuàng)立，是專業(yè)互聯(lián)網(wǎng)技術(shù)服務(wù)公司，擁有項(xiàng)目成都網(wǎng)站設(shè)計(jì)、網(wǎng)站建設(shè)、外貿(mào)網(wǎng)站建設(shè)網(wǎng)站策劃，項(xiàng)目實(shí)施與項(xiàng)目整合能力。我們以讓每一個(gè)夢(mèng)想脫穎而出為使命，1280元互助做網(wǎng)站,已為上家服務(wù),為互助各地企業(yè)和個(gè)人服務(wù),聯(lián)系電話:13518219792

ABAP

class ZCL_SUPER definition public
  create public .
public section.
  methods CONSTRUCTOR .
  methods SET_I
    importing
      !IV_I type INT4 .
protected section.
private section.
  data MV_SUPER type INT4 .
ENDCLASS.
CLASS ZCL_SUPER IMPLEMENTATION.
  method CONSTRUCTOR.
    me->set_i( 100 ).
  endmethod.
  method SET_I.
    me->mv_super = iv_i.
  endmethod.
ENDCLASS. class ZCL_SUB definition public
  inheriting from ZCL_SUPER
  final
  create public .
public section.
  methods PRINT .
  methods SET_I
    redefinition .
protected section.
private section.
  data MV_SUB type I value 1 ##NO_TEXT. ENDCLASS.
CLASS ZCL_SUB IMPLEMENTATION.
  method PRINT. WRITE: / ' sub:' , mv_sub.
  endmethod.
  METHOD set_i. super->set_i( iv_i = iv_i ).
    me->mv_sub = iv_i. WRITE: / 'mv_sub assigned by: ' , iv_i.
  ENDMETHOD.
ENDCLASS. 

測(cè)試：

NEW zcl_sub( )->print( ). 

測(cè)試結(jié)果：sub: 1

Java

public class SuperClass{ private int mSuperX; public SuperClass(){
        setX(99);
    } public void setX(int x){
        mSuperX = x;
    }
} public class SubClass extends SuperClass{ private int mSubX = 1; public SubClass(){} @Override public void setX(int x){ super.setX(x);
        mSubX = x;
        System.out.println("SubX is assigned " + x);
    } public void printX(){
        System.out.println("SubX = " + mSubX);
    }
} 

test:

public static void main(String[] args){
        SubClass sc = new SubClass();
        sc.printX();
    } 

測(cè)試結(jié)果：

JavaScript

function SuperClass(){ this.setX(99);
}

SuperClass.prototype = { mSuperX : 0, setX : function(x){ this.mSuperX = x;
    }
}; function SubClass(){  
    SuperClass.call(this); this.mSubX = 1;
}  

SubClass.prototype = new SuperClass();  

SubClass.prototype.setX = function(x){
        SuperClass.prototype.setX(x); this.mSubX = x; console.log("SubX is assigned " + x);
};

SubClass.prototype.print = function(){ console.log("SubX: " + this.mSubX);
} 

test:

var sub = new SubClass();
sub.print(); 

測(cè)試結(jié)果:

詳細(xì)分析在我的SAP community博客里: A reminder for using constructor in OO world
要獲取更多Jerry的原創(chuàng)技術(shù)文章，請(qǐng)關(guān)注公眾號(hào)"汪子熙"或者掃描下面二維碼: