摘要:本文将带你了解JAVA语言之constructor,希望本文对大家学JAVA有所帮助。
如果constructor里调用了一个成员方法,这个方法被子类override了,当初始化一个子类实例时,父类的构造函数被的调用,此时父类构造函数的上下文里调用的成员方法,是父类的实现还是子类的实现?
你能不用运行代码,就能准确说出这些语句会打印什么出来呢?
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. 测试: NEW zcl_sub( )->print( ). 测试结果: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(); } 测试结果:1 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();
以上就介绍了JAVA的相关知识,希望对JAVA有兴趣的朋友有所帮助。了解更多内容,请关注职坐标编程语言JAVA频道!
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