超级菜鸟问题：什末时候load class - 未名空间MITBBS历史存档

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超级菜鸟问题：什末时候load class

超级菜鸟问题：什末时候load class# Java - 爪哇娇娃

c*i2004-10-14 07:10

1 楼

运行到哪一步装载class?
ClassA MyClass;
MyClass = new ClassA();

c*t2004-10-14 07:10

2 楼

this statement only tells the compiler to reserve a variable space.
^^^^^^^^^^^^^^^^^^^^^^^
here.

【在 c*i 的大作中提到】

: 运行到哪一步装载class?
: ClassA MyClass;
: MyClass = new ClassA();

xt2004-10-14 07:10

3 楼

I believe at run time, ClassA is loaded at this line.

【在 c*****t 的大作中提到】

:
: this statement only tells the compiler to reserve a variable space.
: ^^^^^^^^^^^^^^^^^^^^^^^
: here.

m*t2004-10-14 07:10

4 楼

I think so, too, because there is an implicit null assignment.
I wouldn't be surprised, though, if some VM chooses to optimizes by waiting
until next line, after all, it doesn't really _have to_ load ClassA on this
line.
It's actually fairly easy to find out, just take ClassA off the classpath, and
look at the exception stack trace. 8-)

【在 xt 的大作中提到】

:
: I believe at run time, ClassA is loaded at this line.

g*e2004-10-14 07:10

5 楼

why? JVM does not require classA information for this line.

【在 m******t 的大作中提到】

:
: I think so, too, because there is an implicit null assignment.
: I wouldn't be surprised, though, if some VM chooses to optimizes by waiting
: until next line, after all, it doesn't really _have to_ load ClassA on this
: line.
: It's actually fairly easy to find out, just take ClassA off the classpath, and
: look at the exception stack trace. 8-)

g*e2004-10-14 07:10

6 楼

I just try it. exception occurs in the next line.

【在 g*******e 的大作中提到】

:
: why? JVM does not require classA information for this line.

c*s2004-10-14 07:10

7 楼

非也。
可以做个小试验。在Class.forName里设个断点
ClassA myClass = null;
System.out.println(ClassA.class);
你会发现ClassA在第二行被加载。
另一个方法是在ClassA里加个static块，看看什么时候执行。

【在 xt 的大作中提到】

:
: I believe at run time, ClassA is loaded at this line.

c*t2004-10-14 07:10

8 楼

hehe, if you have done assembly for Java you won't say this :)

【在 xt 的大作中提到】

:
: I believe at run time, ClassA is loaded at this line.