Circular dependencies reference in Java

Hi all,
I would liek to ask that if there were aome effective way of overcoming the circular reference problem is Java ... that is I hav e a class A which has a reference to class B, whereas class B has a reference to class A too, it seems like a "deadlock" situation....class B does not know class A can not compile, whereas class A also know nothing about class B .
I used to over come this by a stupid trick, that is out comment the class A reference is classB first let it compiled and produce a class file ... after that compile class A, add in class A reference in class B again...seems work :)
public class classB{
private classA clsA;
     public classB(classA clsA){
          this.clsA = clsA;
public class classA{
     private classB clsB;
     public classA(){
          clsB = new classB(this);
}I used to overcome this this C++ by the class forward method like using pointer to declare the reference....
But in Java is there an effective way ??? Plz help !!!
p.s. It is said that we should never let circular dependency occurs (bad programming ) ??? but in some situation we really need that....

Isn't a doubly linked list implemented with just a
Node class that has references to previous and next
node? I.e. it's not a case where class A knows about
B, and B knows about A??My point is that circular dependencies are quite common in computer science and I've never heard they're intrinsically bad and should be avoided.
Regarding the A knows about B, and B knows about A case. If you can avoid it basically you've lowered the complexity which is good. But it can also be a question of A is defined in terms of B, and B is defined in terms of A and that could be an elegant recursive definition with low complexity which is good.

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Linux JVM: How to load shared libraries with mutual/circular dependencies

Hi,
I am using the API
System.loadLibrary(String name)
to dynamically link shared libaries to Linux JVM.
The shared libraries has complex circular symbol dependencies among them.
I am not able to load shared libraries due to java.lang.UnsatisfiedLinkError.
Any ideas on how a number of shared libraries with interdependent realtionships
could be successfully linked in to the Linux JVM?
Thanks,
Soumen.
Background
===========
Successful execution of native code within Java virtual machine in a
host platform, has two necessary prerequisites:
Prerequisite 1: The native code is written to the JNI specification
Prerequisite 2: The native code is dynamically linked with Java virtual
machine.
The second step is achieved via simple Java interface, System.loadLibrary:
http://java.sun.com/j2se/1.4.2/docs/api/java/lang/System.html#loadLibrary(java.lang.String)
However, implementation of this interface is highly platform dependent
in regards to exact nature of dynamic linking process.
Tests
=====
I made three shared libraries libfeatureA.so, libfeatureB.so and libfeatureC.so.
Feature A and Feature B are mutually dependent on each other (i.e cicular
dependencies between libfeatureA.so, libfeatureB.so) whereas libfeatureC.so
has no external dependencies.
Case 1
I could link libfeatureC.so with java.
Case 2
Java failed to resolve circular dependency between libfeatureA.so, libfeatureB.so
resulting in linking failure. There may be repackaging workarounds which I have
not yet explored.
Java source code
================
class TestLoadLibrary
static
System.loadLibrary("featureB");
System.loadLibrary("featureA");
System.loadLibrary("featureB");
public static void main(String[] args)
System.out.println("In TestLoadLibrary.main()");
Exception in thread "main" java.lang.UnsatisfiedLinkError: /homes/soumen/work/event/featureB/libfeatureB.so.1.0: /homes/soumen/work/ev B.so.1.0: undefined symbol: featureA_func2
at java.lang.ClassLoader$NativeLibrary.load(Native Method)
at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1737)
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1662)
at java.lang.Runtime.loadLibrary0(Runtime.java:817)
at java.lang.System.loadLibrary(System.java:986)
at TestLoadLibrary.<clinit>(TestLoadLibrary.java:5)

The use of "dlopen() application programming" to achieve dynamic link closure works if there are
no circular dependencies. For example, I have the following dependency:
libfeatureD.so ==> libfeatureC.so
Even if I call Java APIs in correct dependency order, i.e.,
System.loadLibrary("featureC");
System.loadLibrary("featureD");
there would be java.lang.UnsatisfiedLinkError for call System.loadLibrary("featureD").
Now, I have a JNI method implementation, which makes native API call in same dependency order:
dlopen("libfeatureC.so", RTLD_LAZY|RTLD_GLOBAL);
dlopen("libfeatureD.so", RTLD_LAZY|RTLD_GLOBAL);
and now System.loadLibrary calls succeed. Note that I had to set environment
variable LD_LIBRARY_PATH so that dlopen call would find libraries to load.
In other words, from a JNI programming point of view, "linking chasm" has been crossed.
I am looking at circular dependency issue, i.e.,
libfeatureA.so <==> libfeatureB.so
There may be library repackaging workaround.
If anybody knows any workaround, please post.
-Soumen Sarkar
JNI code
========
#include <jni.h>
#include "TestLoadLibrary.h"
#include <stdio.h>
#include <string.h>
#include <dlfcn.h>
JNIEXPORT void JNICALL Java_TestLoadLibrary_libLoadNative
(JNIEnv * jenv, jclass class, jobjectArray libNames)
printf("native: In TestLoadLibrary.libLoadNative()\n");
char linuxLibName[1024];
jsize idx = 0;
jsize nLibs = (*jenv)->GetArrayLength(jenv, libNames);
for(idx = 0; idx < nLibs; ++idx)
/* obtain the current object from the object array */
jobject myObject = (*jenv)->GetObjectArrayElement(jenv, libNames, idx);
/* Convert the object just obtained into a String */
const char libName = (jenv)->GetStringUTFChars(jenv,myObject,0);
strcpy(linuxLibName, "lib");
strcat(linuxLibName, libName);
strcat(linuxLibName, ".so");
printf("\nnative: Trying to open lib with name %s\n", linuxLibName);
void* handle = dlopen(linuxLibName, RTLD_LAZY|RTLD_GLOBAL);
if(handle == 0)
fputs ("\nnative: Could not load lib\n", stderr);
fputs (dlerror(), stderr);
else
printf("\nnative: Loaded lib %s\n", linuxLibName);
/* Free up memory to prevent memory leaks */
(*jenv)->ReleaseStringUTFChars(jenv, myObject, libName);
return;

Circular dependencies and structure

lots of performance problems are caused by convoluted code. circular dependencies between classes, especially large loops lead to problems during the runtime and maintenance. there were no tools on the market that would focus on structural stability of Java software before Small Worlds. it was just released a few weeks ago. check out www.thesmallworlds.com - there is nothing quite like it

Well, it seems he has got an email address:
[email protected]
Could everybody please send thousand copies of an email to this address?

How can I pass a String by reference in java?

Hello!
My question is how to pass a String by reference in java.
I tried to declare my variable, instead of using "String xxx = "f";", I used "String xxx = new String ("f");" :
public static void main (String []args)
String xxx = new String("f");
StatusEnum result2 = getErrorPointStr(xxx);
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buffer.append("123");
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How can I solve this? It is very important, the function will receive String and not something else.
Thanks!

Tolls wrote:
Which is why I said:
Which is why you only managed to change what 'text' referred to in the methodExcept that's not why. Even if String was mutable, doing text = whatever; would have the same effect; it would change what that variable refers to in the method, but it would not change the object's state.
I meant that, since there was no way to actually change the data (ie the char[] or whatever) within the object 'text' referred to, the OP was attempting to change what 'text' referred to and hoping it would be reflected outside the method...which we know won't happen as Java is pass-by-value.\Ah, now I see.
These by-value/by-reference threads tend to get confusing, because usually the person is passing a String, so the immutability of String tends to get in the way and just muddy the waters.

Why we need reference in java?

Hi
I faced one problem while I was doing heapdump analysis.I had to find memory leak suspect.
Somewhere in parent node I have found soft reference.
My question is that why we need reference in java?
and why IBM jdk1.4.2 and above have inbulit class like
softreference
weakreference
phatomreference

These Reference objects have special ways of interacting with the garbage collecor. A normal reference is, in comparison, called a "hard" reference. If an object is only reachable through a special reference it is said to be "softly reachable" or the like, and the garbage collector can collect it. When this happens the reference object is cleared, and will return null if you try to acccess the object through it.
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tks

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@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "argument")
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I need a mechanism to expose action script class reference to java script

I need a mechanism to expose action script class reference to java script

Adobe, I think, are quite happy leaving the StageWebView as a highly efficient and low-level component accessing native functionality, so I wouldn't hold my breath on them extending it.
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See UIWebView as per this thread; http://forums.adobe.com/message/4832821#4832821
http://darkredz.com/ios-uiwebview-and-videoplayer-native-extension-for-air-mobile/
G

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Hello,
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Hi,
Can you try to use the PassThru pipeline on this send port instead of XMLTransmit and share the results. It should not give you this error if
you use PassThru pipeline.
You only need to use XML Transmit when you want to promote any of the to-be-send messages to the context. If you don’t need
to promote any value while sending, then you can use PassThru transmit.
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Please mark as answer or vote as helpful if my reply does

Implementing circular-left shift in java

i'm an fresher currently in a project on SHA algorithm
i would like to know how to implement circular left shift in java
whether there is any method in java to implement this ,
if in case what package i have to import.
please reply me,
yours sincerely
hari hara ganesh.d
india

int number= ...;
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I want to see if anybody has some good ideas on how to solve this.
I have about 20,000 slocs in one main package and about 5 sub-packages.
All of the dialogs in the system originally set the parent component to null(i.e JOptionPane.showConfirmDialog(null,blah...). Which can create problems on some platforms of "loosing" the dialog...
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Depending on where you're constructing your dialogs, you may be able to loop on Component.parent() until you find a Dialog or Frame.

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Hi,
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The JAVA DC is wraped by a lib dc, and it is deployed and used as Library reference in Dynpro DC.
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     at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:160)
     at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:757)
Regards,
TS

How to resolve class reference in java?please join in!!

Hello all!
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class procedure TApp.basemethod(...)//override the method in TObj
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TProp=class(TObj);//TProp inherted from TObj too..;
class procedure TProp.basemethod(...) //override the method in TObj
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constructor TObjlist.Create(AClass : TObjclass);
begin
Itemclass:=AClass;
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itemclass.basemethod(); ////hardly writed in java to invoke class method;
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You need to study the javadocs for java.lang.Class and for java.reflect.*;
Each class in a program has an associated Class object which you can get from the classname as MyClass.class or from an object as myObject.getClass()
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I'm a very seasoned C/C++ developer who's just learning Java. I have this gnawing question that's bugging me. It's rather elementary but it requires someone with experience to answer it.
If I'm delivering a standalone executable (C/C++) to a Windows or Linux customer, it is possible to deliver simply a "*.exe" file (windows) or a Linux Executable file (Linux) which can be installed and run immediately with no dependencies not included in a typical installation. (although, on linux, if there is a gui involved, a typical default Linux install may be missing some dependencies for the gui )
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R2me2 wrote:
"Your questions cause me to suggest that you look into Java Web Start;"
No, this is exactly what I'm not asking. I mean really standalone ....as in the executable runs by itself without user having to install anything else* (via CD, web or anywhere). So I suppose the answer to my question is that NO, there's no such thing in the Java World and that whenever a java program is installed, it always has the JRE as a dependency and that the installation of a java executable is not complete until the JRE is installed.Not to sound like a noob but what were you expecting. Java runs on the JRE and that is what makes it portable as the JRE can be installed almost anywhere o.O
This is not the inconvenience that you are making it out to be. No user is gonna beef with you if they came to you asking for a java application to be installed and I most certainly have played the client role, having to download the latest JRE to run my bank applets. No so long as you provide the user with all the info they need like a link to JRE download etc you will be fine.. :)

Bytes to store object reference in java

How many bytes does java uses to store a reference of an object?
I am calculating the load on my application server from my application.

How many bytes does java uses to store a reference of
an object?
I am calculating the load on my application server
from my application.It depends on the size of the object itself, and its not a easy thing to do :S *sigh
read this...
http://developer.java.sun.com/developer/qow/archive/107/

Circular dependencies reference in Java

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