Queue returns blank strings from template VI

I have created a master VI which creates a named queue, this VI then spawns multiple copies of a template VI. These sub VIs all gain access to the queue and try writing data to it. I understood that the queue VI was protected so this should not cause a problem. Infact this does not work at all, when i extract element within the master VI it only finds a few of the elements and returns blank strings between. Help what is going on. I am not destroying the queue or such, it seems to be a problem with the protection of the queue when using template VIs.
Cheers Tom.

I have not been able to reproduce the problem on LV 6.0.2 Win98. Do you check the error cluster when an empty element is returned? Posting your code might help to find the problem.
LabVIEW, C'est LabVIEW

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Last edited by Pursuit (2010-09-27 23:05:39)

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Try as I might, I can't find any information on how to return two values from a function call (pretty sure I can't in Java).
SO, I tried to find out how to stuff the version string into a string object variable in the class object the DLL API is defined in. I can't figure out how to do that either...
e.g. the following Java code:
class LLDev {
/* --- Load the .DLL -------------------- */
static { System.loadLibrary("LLDev"); }
/* --- Error Codes ---------------------- */
public static final int LLDOk = 0;
public static final int LLDInitErr = -1;
/* --- Public Variables ----------------- */
public static String DLLVersion;
/* --- Public Methods ------------------- */
public native int InitLLDev();
When I invoke LLDev.InitLLDev() from Java I want the C .DLL function Java_LLDev_InitLLDev to put the DLL Version string in the LLDev object's DLLVersion field and return an error code as the function result.
Is this possible???? Is this the right way to do this?? I tried to define the API with methods that return strings instead of integer return codes but the customer using the class wants all of the methods to return a return code in case of some error (e.g. reading the serial number from the device could fail...)

1. In general, the java way to deal with errors is by throwing exceptions, not using return codes. But OK, you are stuck with the user requirement.
2. I suggest you have the native method take as an argument a java object which will accept a string as input. In other words, it has a string "setter".
3. So in your native method, if the function succeeds, it writes your string result to that object, and you can futrther process it when the native method returns a "success" code.
4. There are JNI methods for
o looking up the class of a java object.
o looking up the method of a java class.
o invoking the method.

Return String from values in int array

Hi
I am very new to Java and have been asked to carry out the following task.
Returns a string version of counterGroups. For each
group it gives its number (1 more than its index) and (in
parentheses) the number of counters currently in that group.
Each is followed by two spaces. Thus if there are 3 groups
with 7, 9 and 11 counters the string returned is
"1(7) 2(9) 3(11) "
I have created an array of type int referenced by counterGroups. It stores values 7,9 and 11.
I have made a start on my method but I am struggling. Any help would be appreciated. Please see my method below to see how far I have got. It does not compile.
public String toStr()
String output1;
String temp;
String other;
for (int i=0; i<counterGroups.length(); i++)
int num1 = counterGroups;
output1 = String.valueOf(num1);
other = "(" + output1 + ")";
temp =
int num1 = counterGroups[0];
output1 = String.valueOf(num1);
return "(" + output1 + ")";
regards
Paul

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Paste in the exact error message and clearly indicate which line it's complaining about.

Queue returns blank strings from template VI

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