* How about flash play 8 Garbage Collector working?

Question

Hi, I need to add some Image controls dynamically, yes,the
number of those are unpredictable.
My code to create them like this:
quote:
public function addImg(name:String, x:Number, y:Number):void
var sm1:Image = new Image();
sm1.source = "imgs/down_medium.gif";
sm1.name = name;
sm1.x = x;
sm1.y = y;
this.addChild(sm1);
Then, it appeared in my application. if I add numbers of
Image in my stage, they eat my memory crazily.
so I want to kill some Image which is not in use, but I
crashed.
An Image named "img4kill" in stage, it's index in
this.getChildren() is4, and it holds a image which size is about
230K.
I tried to kill it like this:
quote:
this.removeChildAt(4);
yes, it's remove from the stage in faith, but I watched the
memory that the browser using, before and after killing it.
I found the memory it takes is not released.
How can I kill it from both the stage and memory ? I tried
the global function "delete" ,but failed too.
I know that flash play 8.5 and later use a powerfull
GC(garbage collector), but in the sample above, it dose't work for
me.
who can save me from this mud layer?any ideas?
thanks a lot .
(sorry about my ugly english)
[email protected]

Answer 1

Don't worry, the garbage collector will work very well in this case (and in every other case too :) ). It will only collect an object when no more references are pointing to it. Your array still holds a reference to all the items it contains (unless you explicitly do array[index] = null).
There are only three ways that I know of to destroy a reference to an Object: 1). Set the reference to null 2). Let the reference fall out of scope 3) reassign the reference to another object
The garbage collector will also be able to collect objects that have a cyclical references as long as none of the objects in the cycle are reachable.
It pays to understand the ins and outs of garbage collection and memory management in the VM. Knowing that will let you know, for example, that allocating an Object in Java is a very cheap operation (while it is pretty expensive in C/C++).
Check http://www.ibm.com/developerworks/java/library/j-jtp10283/ and http://www.ibm.com/developerworks/java/library/j-jtp11253/ and for more details about the GC
Also don't worry about the performance impact of setters and getters, either the javac compiler or the Virtual Machines Just In Time Compiler will inline those small methods.
In short don't worry about such low level performance problems and concentrate on your coding style and algorithms. The Hotspot JVM is an amazingly efficient piece of software. It also include a lot of optimizations that work very well in optimizing "standard" code. The more normally you code, the faster your program will be, so don't try clever optimizations tricks, they probably won't work well in java.
Read the following articles for some discussion about performance in Java:
http://www.ibm.com/developerworks/java/library/j-jtp04223.html
http://www.ibm.com/developerworks/java/library/j-jtp09275.html
http://www.ibm.com/developerworks/java/library/j-jtp01274.html