1. LiuPu
12月29日 上午10时34分 显示选项
新闻论坛：comp.object
发件人： "LiuPu" <Liup...@gmail.com> - 查找此作者的帖子
日期：28 Dec 2005 18:34:19 -0800
当地时间：2005年12月29日(星期四) 上午10时34分
主题：I can't explain this
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// A.java
public abstract class A{
public String str = "AAA";
}
// B.java
public B extends A{
A a = new B();
public static void main(String[] args){
A b = new B();
}
}
When I use "java B" , the error "java.lang.StackOverflowError" appears.
I can't explain this.
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2. iamfrac...@hotmail.com
12月29日 下午4时37分 显示选项
新闻论坛：comp.object
发件人： iamfrac...@hotmail.com - 查找此作者的帖子
日期：29 Dec 2005 00:37:01 -0800
当地时间：2005年12月29日(星期四) 下午4时37分
主题：Re: I can't explain this
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LiuPu skrev:
> // A.java
> public abstract class A{
> public String str = "AAA";
> }
> // B.java
> public B extends A{
> A a = new B();
> public static void main(String[] args){
> A b = new B();
> }
> }
> When I use "java B" , the error "java.lang.StackOverflowError" appears.
> I can't explain this.
Hej!
Firstly, this has nothing to do with inheritence; you can see the
problem in its simplest form in the following class:
class Test {
Test anotherTest = new Test();
public static void main(String[] args) {
Test test = new Test();
}
}
The problem is cause because every Test object is creating another Test
object, leading to an attempt to create an infinite amount of Test
objects.
So, in the main() method, the JVM pushes the execution context onto the
stack when it calls the Test() constructor; but this will first attempt
to initialise all field variables in Test, and the only field variable
is another Test object. When this Test() constructor is called, yet
another execution context must be pushed onto the stack, etc.
In the end, the stack is filled and the JVM says goodbye.
If you actually want your B object to hold a reference to another A
object, then you'll have to declare the field variable as equal to
null, and add the appropriate referenced A object after the B object is
initialised (e.g., with a setter method).
.ed
--
www.EdmundKirwan.com - Home of The Fractal Class Composition.
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3. Penny Liang
12月29日 下午7时46分 显示选项
新闻论坛：comp.object
发件人： "Penny Liang" <pennyliang...@software.nju.edu.cn> - 查找此作者的帖子
日期：Thu, 29 Dec 2005 19:46:08 +0800
当地时间：2005年12月29日(星期四) 下午7时46分
主题：Re: I can't explain this
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for extends A, B has a static relation with A because of inheritance,
for contain a reference of A,B has a dynamic relation with A, because of
reference.
let's see the construciton of B
create A(for extends)
create B(for reference)
create A(for extends)
create B(for reference)
........
........
the StackOverflowError occures because of the construction function of B
--
Thanks & Regards,
Penny Liang
Email:jackli...@vip.sina.com;pennyliang...@software.nju.edu.cn
"LiuPu" <Liup...@gmail.com> ????
news:1135823659.216804.243720@o13g2000cwo.googlegroups.com...
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> // A.java
> public abstract class A{
> public String str = "AAA";
> }
> // B.java
> public B extends A{
> A a = new B();
> public static void main(String[] args){
> A b = new B();
> }
> }
> When I use "java B" , the error "java.lang.StackOverflowError" appears.
> I can't explain this.
回复
4. LiuPu
12月30日 下午1时36分 显示选项
新闻论坛：comp.object
发件人： "LiuPu" <Liup...@gmail.com> - 查找此作者的帖子
日期：29 Dec 2005 21:36:42 -0800
当地时间：2005年12月30日(星期五) 下午1时36分
主题：Re: I can't explain this
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Thank you for your answers. Now I know the problem and its answer.
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2005/12/31 11:57:00
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面向对象构造关于reference的静态构造异常[含我的回帖]
