C++,C#,Java继承机制的不同(2)

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3. 将test方法改为virtual方法
结果如下：

in father's constructor!

father's a: 10

father's b: father's b

father's test

out father's constructor



in son's constructor!

son's a: 10

son's b: son's b

son's test

out son's constructor



f.a : 10

f.b : father's b

son's test

Press any key to continue

结论如下:
virtual 方法（参数相同）调用时指代由子类的实现决定，但属性仍由对象的声明类型决定，this指代仍由当前类决定。

4. 子类的方法参数不同的情况
将子类的test方法改为:

void test(int i, float j);

结果如下:

in father's constructor!

father's a: 10

father's b: father's b

father's test

out father's constructor



in son's constructor!

son's a: 10

son's b: son's b

son's test

out son's constructor



f.a : 10

f.b : father's b

father's test

Press any key to continue

结论如下:
对于参数不同或者参数返回值不同的vitual方法，指代由父类决定

C#的实现与结果(编译器:.net 2003)
1. 代码：
using System;



namespace inheritence_test

{

/// <summary>

/// Summary description for inheritence.

/// </summary>

public class father

{

public father()

{

//

// TODO: Add constructor logic here

//

Console.WriteLine("in father's constructor!");

Console.WriteLine(this.x+"");

Console.WriteLine(this.str+"");

this.test(1,1);

Console.WriteLine("out father's constructor!\n");

}



public void test(int i,int j){

Console.WriteLine("this is father's test");

}

public int x=10;

public String str="father's string";

}



}

using System;



namespace inheritence_test

{

/// <summary>

///

/// </summary>

public class son : father

{

public son()

{

//

// TODO: Add constructor logic here

//

Console.WriteLine("in son's constructor!");

Console.WriteLine(this.x+"");

Console.WriteLine(this.str+"");

this.test(1,1);

Console.WriteLine("out son's constructor!\n");

}

public void test(int i,int j)

{

Console.WriteLine("this is son's test");

}

public int x=0;

public String str="son's string";

}

}

private void button1_Click(object sender, System.EventArgs e)

{

father f=new son();

Console.WriteLine("f.x : "+f.x+"\n");

Console.WriteLine("f.str : "+f.str+"\n");

f.test(1,1);

}

in father's constructor!

10

father's string

this is father's test

out father's constructor!



in son's constructor!

0

son's string

this is son's test

out son's constructor!



f.x : 10

f.str : father's string

this is father's test

2. 结论如下：
a. 无论针对父类的方法（非virtual）还是属性其指代均由指针或者对象的声明类型决定

b. this的指代由当前类型决定

3. 将test方法改为virtual方法
virtual public void test(int i,int j){

Console.WriteLine("this is father's test");

}

运行结果同上

将子类的方法声明为override

override public void test(int i,int j)

{

Console.WriteLine("this is son's test");

}

结果如下：

in father's constructor!

10

father's string

this is son's test

out father's constructor!



in son's constructor!

0

son's string

this is son's test

out son's constructor!



f.x : 10

f.str : father's string

this is son's test

4. 结论：
只有在子类使用了override关键字之后，才能实现C++的virtual结构,其他指代同c++





java的实现与结果(编译器: JB7 Visualage for java 3.5)
1. 代码：
public class father {



public father() {

System.out.println("in father's constructor!");

System.out.println(this.x+"");

System.out.println(this.str+"");

this.test(1,1);

System.out.println("out father's constructor!\n");

}

public void test(int i,int j){

System.out.println("this is father's test");

}

public int x=10;

public String str="father's string";

public static void main(String[] args) {

father father1 = new father();

}

}

package test;



/**

* <p>Title: </p>

* <p>Description: </p>

* <p>Copyright: Copyright (c) 2003</p>

* <p>Company: </p>

* @author unascribed

* @version 1.0

*/



public class son extends father{



public son() {

System.out.println("in son's constructor!");

System.out.println(this.a+"");

System.out.println(this.b+"");

this.test(1,1);

System.out.println("out son's constructor!\n");

}

public int a=0;

public String b="son's b";

public void test(int i,int j){

System.out.println("this is son's test");

}

public static void main(String[] args) {

father f = new son();

System.out.println("f.x : "+f.x+"");

System.out.println("f.str : "+f.str+"");

f.test(1,1);

}

}

2. 结果(请注意this的指代):
in father's constructor!


10


father's string


this is son's test


out father's constructor!





in son's constructor!


0


son's b


this is son's test


out son's constructor!





f.x : 10


f.str : father's string


this is son's test


3. 结论：
在指代上同C++的virtual 方法，但this的指代由方法由实现的对象决定（这里是子类）属性由对象的类型决定（这里是父类）。