Java Array/Variable question

I posted in the wrong forum maybe. I have a post in the learning/training area at Using multiple variable names in a for statement?
Can anyone from this forum give any input as well and post it on that thread? Thanks!

Done. You should use the solution that has already been suggested.

Similar Messages

[JNI Beginner] GC of Java arrays returned by the native code

Hello all,
I am beginning with JNI, to integrate a C library that pilots an industrial equipment, into a java UI. This library enables to exchange various proprietary PDUs (protocol data units), with the equipment, up and down (request/replies). Both requests and replies are arrays of bytes (+char*+).
"Request" byte arrays are constructed by Java code, which passes them to the JNI code that glues with the lib. "Reply" byte arrays are returned to the Java code, which analyzes them.
The "return reply" part is very similar to this [tutorial example|http://java.sun.com/developer/onlineTraining/Programming/JDCBook/jniexamp.html] , which returns bytes read from a file. However there's something I don't understand with regard to garbage collection of the returned byte array:
- in this stock example, the C code creates a Java byte array fills it, and simply returns it (example code stripped to highlight only the parts relevant to my question):
    jByteArray=(*env)->NewByteArray(env, size);
    (*env)->SetByteArrayRegion(env, jByteArray, 0, size, (jbyte *)sourceBytes);
    return (jByteArray);What will happen to this Java array (jByteArray) with regard to garbage collection?
- if it's no more referenced (the example Java code just systemouts it and forgets it), will it be eligible to GC?
- if it is referenced by a Java variable (in my case, I plan to keep a reference to several replies as the business logic requires to analyze several of them together), do regular Java language GC rules apply, and prevent eligibility of the array to GC as long as it's referenced?
That may sound obvious, but what mixes me up is that the same tutorial describes memory issues in subsequent chapters: spécifically, the section on "passing arrays states that:
[in the example] the array is returned to the calling Java language method, which in turn, garbage collects the reference to the array when it is no longer usedThis seems to answer "yes" to both my questions above :o) But it goes on:
The array can be explicitly freed with the following call:
{code} (*env)-> ReleaseByteArrayElements(env, jByteArray, (jbyte *)sourceBytes, 0);{code}Under what circumstances would one need to explicitly free jByteArray when it's about to be returned to the Java calling method? Or does this sentence apply to completely different situations (such as, when the array is +not+ returned as is to a Java method)?
The tutorial's next section has a much-expected +memory issues+ paragraph, from which I quote:
By default, JNI uses local references when creating objects inside a native method. This means when the method returns, the references are eligible to be garbage collected.I assume this means, +unless the references are assigned, in the Java code, to a Java variable+, right?
If you want an object to persist across native method calls, use a global reference instead. A global reference is created from a local reference by calling NewGlobalReference on the the local reference.I assume this enables the C code to maintain a global reference to a java object even if it's not referenced anymore from the Java variables, right?
I also checked the [JNI specification|http://download-llnw.oracle.com/javase/6/docs/technotes/guides/jni/spec/design.html#wp1242] , but this didn't clear the doubt completely:
*Global and Local References*
The JNI divides object references used by the native code into two categories: local and global references. Local references are valid for the duration of a native method call, and are automatically freed after the native method returns. Global references remain valid until they are explicitly freed.
Objects are passed to native methods as local references. All Java objects returned by JNI functions are local references. The JNI allows the programmer to create global references from local references. JNI functions that expect Java objects accept both global and local references. A native method may return a local or global reference to the VM as its resultAgain I assume the intent is that Global references are meant for objects that have to survive across native calls, regardless of whether they are referenced by Java code. But what worries me is that combining both sentences end up in +All Java objects returned by JNI functions are local references (...) and are automatically freed after the native method returns.+.
Could you clarify how to make sure that my Java byte arrays, be they allocated in C code, behave consistently with a Java array allocated in Java code (I'm familiar already with GC of "regular" Java objects)?
Thanks in advance, and best regards,
J.

jduprez wrote:
Hello all,
I am beginning with JNI, to integrate a C library that pilots an industrial equipment, into a java UI. This library enables to exchange various proprietary PDUs (protocol data units), with the equipment, up and down (request/replies). Both requests and replies are arrays of bytes (+char*+).
"Request" byte arrays are constructed by Java code, which passes them to the JNI code that glues with the lib. "Reply" byte arrays are returned to the Java code, which analyzes them.
The "return reply" part is very similar to this [tutorial example|http://java.sun.com/developer/onlineTraining/Programming/JDCBook/jniexamp.html] , which returns bytes read from a file. However there's something I don't understand with regard to garbage collection of the returned byte array:
- in this stock example, the C code creates a Java byte array fills it, and simply returns it (example code stripped to highlight only the parts relevant to my question):
    jByteArray=(*env)->NewByteArray(env, size);
(*env)->SetByteArrayRegion(env, jByteArray, 0, size, (jbyte *)sourceBytes);
return (jByteArray);What will happen to this Java array (jByteArray) with regard to garbage collection?It will be collected when it is no longer referenced.
The fact that you created it in jni doesn't change that.
The array can be explicitly freed with the following call:
(*env)-> ReleaseByteArrayElements(env, jByteArray, (jbyte *)sourceBytes, 0);Under what circumstances would one need to explicitly free jByteArray when it's about to be returned to the Java calling method? Or does this sentence apply to completely different situations (such as, when the array is not returned as is to a Java method)?
Per what the tutorial says it is either poorly worded or just wrong.
An array which has been properly initialized it a just a java object. Thus it can be freed like any other object.
Per your original question that does not concern you because you return it.
In terms of why you need to explicitly free local references.
[http://download-llnw.oracle.com/javase/6/docs/technotes/guides/jni/spec/design.html#wp16785]
The tutorial's next section has a much-expected memory issues paragraph, from which I quote:
By default, JNI uses local references when creating objects inside a native method. This means when the method returns, the references are eligible to be garbage collected.I assume this means, unless the references are assigned, in the Java code, to a Java variable, right?As stated it is not precise.
The created objects are tracked by the VM. When they are eligible to be collected they are.
If you create a local reference and do NOTHING that creates an active reference elsewhere then when the executing thread returns to the VM then the local references are eligible to be collected.
>
If you want an object to persist across native method calls, use a global reference instead. A global reference is created from a local reference by calling NewGlobalReference on the the local reference.That is not precise. The scope is the executing thread. You can pass a local reference to another method without problem.
I assume this enables the C code to maintain a global reference to a java object even if it's not referenced anymore from the Java variables, right?
It enables access to it to be insured across multiple threads in terms of execution scope. Normally you should not use them.

Working with array variables defined in the BPM process

Hello,
I have created an array variable in my process. This array was created based on a custom type that contains 2 strings variables.
How can I set/get and add new items to this array variable using java code?
The only thing I know is that, if this was a simple variable I would do something like this:
DCBindingContainer bc = (DCBindingContainer)FacesContext.getCurrentInstance().getApplication().evaluateExpressionGet(FacesContext.getCurrentInstance(), "#{bindings}", BindingContainer.class);
JUCtrlAttrsBinding dc = (JUCtrlAttrsBinding) bc.findNamedObject("myVar");
dc.setInputValue("theValue".toString());
thank you
fwu

Hi
I've been working on TZ's recently... see this post:
https://supportforums.cisco.com/discussion/12474756/how-check-daylight-saving-within-uccx-script
My approach in the scripts was that basically I allow the department to set their opening hours in the timezone of their choice.
They have a management web page served from CCX that accepts start/end times each day, and a timezone. That all gets stored in XML.
In the script, based on that information I get the current time in whatever timezone is set, and compare that to the XML open/close times.
Similarly for holidays, I get the current date/time in the holiday TZ and compare the holidays to that.
Aaron

Manipulating java array object in an oracle procedure

hi there,
i have a java store procedure that returns an array of filenames, and i have an oracle stored procedure that will for each filename returned in the java array object, open that file do some processing and load the data into database tables, now my question is, would an oracle 9i varray object be compatible with a java array, or should i pass in a pl/sql table to store the filnames returned?
i really am stuck at this point and need help !!!!
Thanx

Wole,
Have you searched the code samples available at the Technet Web site? Could you not find a relevant one?
Have you tried searching the Ask Tom Web site?
Good Luck,
Avi.

Java arrays contiguous in memory?

are java arrays always contiguous in memory? or how does java save his arrays?
i need to know because i wrote an algorithm with a lot of array length changing, and i wonder if it consumes a lot or not, maybe java uses virtual memory arrays like those here :
http://developers.sun.com/solaris/articles/virtual_memory_arrays.html
any answer is welcome,
Nck.

The internal layout of objects (including arrays) is explicitly undefined by the JVM standard:
http://java.sun.com/docs/books/vmspec/2nd-edition/html/Overview.doc.html#16066
So you can't assume that arrays are implemented in any particular way on any given JVM. But the Get<Type>ArrayElements JNI functions can give you a clue about it for the current JVM.
But I don't really understand the background of the question. What do you mean by "a lot of array length changing"? Java arrays can't be resized, whether from bytecode or JNI.
-slj-

The Mysterious java array implementation

In java when we create an array of primitive data type
e.g long[] x = new long[10];
we can reterieve the lenght of the array using x.length. Does someone know where this variable length is declared. As in java arrays are implemented as an Objects. Even i treid to find out the class reference variable "x" belongs to, and I came to know that it is "[J" and this class implements Cloneable and Seriaziable interface. But there is no field or variable like "length".

Java-Aspirant wrote:
. Even i treid to find out the class reference variable "x" belongs to, and I came to know that it is "[J" and this class implements Cloneable and Seriaziable interface. But there is no field or variable like "length".
If you want to use reflection on arrays, there's [java.lang.reflect.Array|http://java.sun.com/javase/6/docs/api/java/lang/reflect/Array.html which allows you to interrogate the length pseudo-field and access elements.

Incrementing an array variable!!!

Hello,
I wanna know if we can increment an array variable by more than 1.
When I use for(i=0;i<10;i+4) it is giving me an error.Just wanted to know if we can increment an array variable by any value other than 1.
Thanks

Your are right, I see that thank you
Ok sorry guys for pasting the assignment. I have done some thing but me not sure weather I am doing right way or not. here is my code. And by the way how to return the integer to the main function "public static void main(String args[]){" from static integer function "static int isCentered(int[] a){"
Code for Q. 1)
Out put:
{1,2,3,4,5} => 0(the middle element 3 is not strictly less than all other elements)
{3,2,1,4,5} => 1(the middle element 1 is strictly less than all other elements)=>
{3,2,1,4,1} => 0(the middle element 1 is strictly less than all other elements)
{3,2,1,14,6} => 0(no middle element since array has even number of elements)
{} => 0(no middle element)
{1} => 1(satisfies the condition vacuously)
import java.io.*;
public class isCenteredArray{
public static void main(String args[]){
isCentered(new int[]{1, 2, 3, 4, 5});
isCentered(new int[]{3, 2, 1, 4, 5});
isCentered(new int[]{3, 2, 1, 4, 1});
isCentered(new int[]{3, 2, 1, 1, 4, 6});
isCentered(new int[]{});
isCentered(new int[]{1});
static int isCentered(int[] a){
int ar=0;
if(a.length%2 ==0){
return ar;
int j=1;
for (int i=0; i<a.length; i++){
if(j != a.length/2){
if(a[i] > a[a.length/2]){
ar = 1;
}else{
ar = 0;
return ar;
j=j+1;     }
return ar;
Code for Q. 2)
Out put:
{1,2,3,0} => 1(because 1+2 = =3+0= =3)
{1,2,2,1,3,0} => 1(because 1+2 = =2+1= =3+0= =3)
{1,1,2,2} => 0(because 1+1 = =2 != 2+2)
{1,2,1} => 0(because array does not have any even number of elements)
{} => 1
import java.io.*;
public class isDualArray{
public static void main(String args[]){
isDual(new int[]{1, 2, 3, 0});
isDual(new int[]{1, 2, 2, 1, 3, 0});
isDual(new int[]{1, 1, 2, 2});
isDual(new int[]{1, 2, 1});
isDual(new int[]{});
static int isDual(int[] a){
int ar=0;
for(int i=0; i<=a.length; i++){
if(i%2 !=0){
if((a[i-1] + a) == a[i+1]){
ar = 1;
}else{
ar = 0;
return ar;
return ar;
Code for Q. 3)
Out put:
{1} => 1(true vacuously)
{2} => 0(contains no odd elements)
{1,1,1,1,1,1} => 1
{2,4,6,8,11} => 1
{-2,-4,-6,-8,-11} => 0
import java.io.*;
public class idOddHeavyArray{
public static void main(String args[]){
isOddHeavy(new int[]{1});
isOddHeavy(new int[]{2});
isOddHeavy(new int[]{1, 1, 1, 1, 1, 1});
isOddHeavy(new int[]{2, 4, 6, 8, 11});
isOddHeavy(new int[]{-2, -4, -6, -8, -11});
static int isOddHeavy(int[] a){
int ar=0;
int oddheavynumber=0;
for (int i=0; i<a.length; i++){
if(a>oddheavynumber){
oddheavynumber = a[i];
     }else{
oddheavynumber=oddheavynumber;
if(oddheavynumber%2==0){
ar=0;
     }else{
ar=1;
System.out.println(ar);
return ar;
Please check the way out how I did and let me know if I am going the wrong way...
Thanks,
Indoman

How do I use an array variable in the assignment target?

Hi,
I am creating a BPEL process in which I have to use an array variable. The array variable needs to be initialized based on some condition.
The issue is I cannot find a way to set the value of the array variable. There are ways to GET the value of an array variable indexing into it.
But how do I set the value by using the Array variable in the <to> tag?
Any help is appreciated. I am using BPEL 10.1.2.0.2.
Thanks.

You can declare a variable of type integer which will server as your index. Figure out based on some condition in your process which index of array to update. Assign to your integer variable you created.
And have Assign copy operation like this -
<copy>
<from variable="Var_Output_FetchDueDate"
part="OutputParameters"
query="/ns18:OutputParameters/ns18:DUEDATE"/>
<to variable="outputVariable" part="payload"
query="/client:GetCustomerAccountInformationProcessResponse/client:customer/client:accounts/client:account[$Var_Counter]/client:dueDate"/>
</copy>
I have been using this in my processes.

How do I load values from a database column to an array variable in TS?

I'm trying to get the values from the column in a database into an array variable in TS using the property loader.
The Open Database, Open SQL Statement, and Property loader steps all complete and say "done". But my array is empty when it's all over.
Using TestStand 2010
Microsoft SQL Management Express 2008
Database configured by my company, I can not change it only read from it.
Thank you,
Newb-D

The database has to be in a form that will work with the PropertyLoader and it sounds like it isn't.
Try using the Import/Export Properties tool found in the Tool menu, to export some data to a database and then you can see if your database is compatible.
My guess is you will have to write your own loader.
Regards
Ray Farmer

How to access a JAVA Script variable in JSP Code

How to access a JAVA Script variable in JSP Code. I have been unable todo this.
Plz Suggest a way.
Thanks
Soumya

try to do this code
String s=request.getParameter("javascriptvariablename");

How to use array variable in Oracle

Hi,
I want to use a array variable to store many string values i.e. values like ( "my name is hhhyy and i have a tack", "My data is valid" , "hhggg gaya hujjjs")
currently all these values are in seperate variables , I want to consolidate them in one array and use it in further , after replacing some values from them.
I want to take data too. I am thinking of using "Varchar array" with values are in one cursor i want to take them in single array.
varchar array is throwing some exception once it has taken all the value. I had extended it upto 100 values.
What could be the possible solution.
create or replace function testet
( value varchar2) return varchar2
as
x_value Varchar2(2000);
x_value2 varchar2_array := varchar2_array();
x_value3 number;
cursor c1 is
SELECT val
FROM table A
WHERE A.coulmn= 'val';
begin
x_value2.EXTEND(100);
x_value3 := 1;
for indx IN c1
loop
x_value2(x_value3):= indx.val;
dbms_output.put_line(x_value2(x_value3));
x_value3 := x_value3 + 1;
end loop ;
end;

user12403816 wrote:
actual error :
ORA-06533: Subscript beyound count
ORA - 06512 " at Function name , line 23
ora - 06512: at line 3
06533, 00000, "Subscript beyond count"
// *Cause: An in-limit subscript was greater than the count of a varray
// or too large for a nested table.
// *Action: Check the program logic and explicitly extend if necessary.code contains bug.
after code is fixed, then no error gets thrown

Mapping Java Arrays

I was given an object model generated by an apache product, Axis. The generated java files use the Java Array in the following fashion:
Class Zoo {
private ArrayOfAnimals animals;
// â¦ public get/set methods cut
Class ArrayOfAnimals {
private Animal animals[];
// â¦ public get/set methods cut
Class Animal {
private String name;
// â¦ public get/set methods cut
I was tasked with mapping the one-to-many relationship between zoo and an array of animals using the Animal array. I canât find a mapping in TopLink to do this type of association. I am NOT allowed to modify the generated source code. I may be able to extend the generated classes, and perhaps provide a different superclass.
I am allowed to create the relational model for these domain classes. Can anyone help with this type of mapping?
Thanks

TopLink does not directly support arrays as the mapping type for a collection, only collection types that support the Collection and Map interfaces.
In general it seems odd to use an array instead of a Java collection which would be much more efficient (in terms of adding and removing) and much more functional. I would definitely suggest changing the generated code, or the way the code is generated if at all possible.
The easiest way to map the array in TopLink would be the use get/set methods for the 1-m mapping on the Zoo class that converted the array to/from a Collection.
i.e. something like,
public List getAnimalsList() {
return new Arrays.asList(animals.animals);
public void setAnimalsList(List list) {
animals.animals = (Animal[]) list.toArray();
In general TopLink uses its ContainerPolicy class to handle collections. It may also be possible (but advanced) to write a custom container policy for your 1-m mapping that handles arrays.

Conversion of java Array to oracle SQL Array while calling Stored Procedure

How java Array can be converted to oracle SQL array while calling Stored procedure with callable statement.
i.e java Array ---> Sql Array in Oracle while setting the datatypes to callable statement arguments.

Look at:
http://forum.java.sun.com/thread.jsp?forum=48&thread=376735&tstart=0&trange=15
Paul

How to call a C sort function to sort a Java Array.

My name is David, I'm interning this summer doing some High Performance Computing work. I'm significantly out of my comfort zone here; I am primarily a network/network security geek, not a programming guy. I took one Java based class called problem solving with programming where we wrote like 3 programs in Java and did everything else in pseudocode and using a program called Alice http://www.alice.org/ to do things graphically. Learned basically no actual programming syntax. Also have done some self-taught perl, but only through one book and I didn't finish it, I only got about half way through it. So my expertise in programming are pretty much null.
That being said, I currently am tasked with having to figure out how to make JNI work... specifically at this time I am tasked with writing an array in Java, and designing a C program that can be called by means of JNI to sort the array. I have chosen to work with the Merge Sort algorithm. My method of coding is not one where I write the entire thing from scratch, I don't particularly have a need to master languages at this point, rather I just need to make them work. I am interested in learning, but time is of the essence for me right now. So thus far what I have done is take sample codes and tweak them to meet my purpose. However, I currently am unable to make things work. So I am asking for help.
I am going to paste 3 codes here, the first one will be my basic self-written instructions for JNI (Hello World Instructions), the second one will be my Java Array, and the third one will be my MergeSort function. I am not asking for you to DO my work for me by telling me how to manipulate my code, but rather I am asking for you to send me in the direction of resources that will be of some aid to me. Links, books (preferrably e-books so I don't have to go to a library), anything that you can send my direction that may help will be deeply appreciated. Thanks so much!
JNI Instructions:
/*The process for calling a C function in Java is as follows:
1)Write the Java Program name. Eg. HelloWorld.java
2)Compile it: javac HelloWorld.java
3)Create a header file: javah -jni HelloWorld
4)Create a C program eg. HelloWorld.java
5)Compile the C program creating a shared library eg. libhello.so (My specifc command is cc -m32 -I/usr/java/jdk1.7.0_05/include -I/usr/java/jdk1.7.0_05/include/linux -shared -o libhello.so -fPIC HelloWorld.c
6) Copy the library to the java.library.path, or LD_LIBRARY_PATH (in my case I have set it to /usr/local/lib.
7)Run ldconfig (/sbin/ldconfig)
8)Run the java program: java HelloWorld. */
//Writing the code:
//For the HelloWorld program:
//In java:
//You need to name a class:
class HelloWorld {
//You then need to declare a native method:
public native void displayHelloWorld();
//You now need a static initializer:
static {
//Load the library:
System.loadLibrary("hello");
/*Main function to call the native method (call the C code)*/
public static void main(String[] args) {
new HelloWorld().displayHelloWorld();
//In C:
#include <jni.h> //JNI header
#include "HelloWorld.h" //Header created by the javah -jni command parameter
#include <stdio.h> //Standard input/output header for C.
//Now we must use a portion of the code provided by the JNI header.
JNIEXPORT void JNICALL
Java_HelloWorld_displayHelloWorld(JNIENV *env, jobject obj)
//Naming convention: Java_JavaProgramName_displayCProgramName
    printf("Hello World!\n");
    return;
}Java Array:
class JavaArray {
     private native int MergeSort(int[] arr);
     public static void main(String[] args)
         int arr[] = {7, 8, 6, 3, 1, 19, 20, 13, 27, 4};
     static
         System.loadLibrary("MergeSort");
}Hacked and pieced together crappy C Merge Sort code:
#include <jni.h>
#include <stdio.h>
#include "JavaArray.h"
JNIEXPORT jint JNICALL
Java_JavaArray_MergeSort(JNIEnv *env, jobject obj, jintArray arr[],jint low,jint mid,jint high)
   jint i,j,k,l,b[10];
l=low;
i=low;
j=mid+1;
while((l<=mid)&&(j<=high))
    if(arr[l]<=arr[j])
       b=arr[l];
l++;
else
b[i]=arr[j];
j++;
i++;
if(l>mid)
for(k=j;k<=high;k++)
b[i]=arr[k];
i++;
else
for(k=l;k<=mid;k++)
b[i]=arr[k];
i++;
for(k=low;k<=high;k++)
arr[k]=b[k];
void partition(jint arr[],jint low,jint high)
jint mid;
if(low<high)
mid=(low+high)/2;
partition(arr,low,mid);
partition(arr,mid+1,high);
sort(arr,low,mid,high);

You're doing OK so far up to here:
Java_JavaArray_MergeSort(JNIEnv *env, jobject obj, jintArray arr[],jint low,jint mid,jint high)This is not correct. It is not what was generated by javah. It would have generated this:
Java_JavaArray_MergeSort(JNIEnv *env, jobject obj, jintArray arr,jint low,jint mid,jint high)A 'jintArray' is already an array, embedded in an object. You don't have an array of them.
So you need to restore that, and the header file, the way 'javah' generated them, then adjust your code to call GetIntArrayElements() to get the elements out of 'arr' into a local int[] array, sort that, and then call ReleaseIntArrayElements() to put them back.

How to use array variable in Business Rule

Hi,
I have read a lot about Array variable. But everywhere declaration of array variable in described. I can declare that. It works fine. But i can't implement that array variable.
Can any one please provide me an example of implementation of array variable?
Regards,
Rubi
Edited by: Rubi Banerjee on Mar 30, 2012 3:35 AM

forget about all varible in essbase CSC
it's bad practics.^^^Is it?
Essbase cube are self big array )^^^That's what makes ARRAY so cool -- you can set up an array that encompasses a dimension.
Example straight from a HBR:
ARRAY SomeArray["Entity"] ;
Regards,
Cameron Lackpour

Java Array/Variable question

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