Final as argument to a method....

Hi ,
For example .. i have the following method(constructor) - which is supposed to create a new sphere from an existing one:
Sphere(*final* Sphere oldSphere) {
radius = oldSphere.radius;
xCenter = oldSphere.xCenter;
yCenter = oldSphere.yCenter;
zCenter = oldSphere.yCenter;Additionally... i have the following questions....
1) In such situations... do we have to declare the class+object (oldSphere in the above example) as final....????
I mean whenerver we compare/copy/ ..e.t.c. one object with another one of the same class and this is done via a method then we have to use the final word....as qualifier to the existing object...???
2) Why do we use the final .. here??? In order to secure that it would not be changed during the exec of the above method (for example...)?
Thanks...
Sim

sgalaxy wrote:
2) Why do we use the final .. here??? In order to secure that it would not be changed during the exec of the above method (for example...)?Yes, to ensure that the local variable doesn't change during the method. You may be asking why this is necessary.
It's necessary to support nested classes. Nested classes can only use final local variables from the wrapping method.
Here's why. (This gets kind of esoteric.) Since they're final, the nested class can simply add its own final copy of the variable, and all will be correct. If it weren't final, then the nested class would have to maintain a reference back to the local variable, and that class might end up living longer than the invocation of the method. This could result in things on the heap referring to stack frames, which is a bad thing for reasons that are too complicated to go into right now. To support that, the entire Java execution model would have to change. So it's much simpler to require that nested classes can only use local variables in the wrapping method if the local variables are final.
If you want to learn more about this, read about the JVM, in particular how the JVM uses its heap and a collection of stacks (one per thread), and how they interact during execution of java code. Then it wouldn't hurt to read about how, say, a Scheme environment executes code, and then compare the two.
You don't really need to know all that much detail to code, although it helps.

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Thread Safety : Marking arguments of static method as final

Hi,
I have a class with static method. This class will be hit by several threads and I need to make the code thread safe. If I declare the arguments of this method as "final", will it guratnee that these variables cannot be changed by another thread calling this method?
Thanks in advance,
Rtameh

No, the only condtion where parameters or local variables might be shared with another thread is if you create a local class which uses them, and the compiler won't allow you to do that if they aren't final.
Local variables are always thread-safe.

Maximum # of arguments for a method

Is there a maximum # of arguments for a method?
I have the following signature for a method:
void process_l1_queue(int processnum, Scheduler level1[], Scheduler[] level2[], Scheduler[] level3[],Scheduler[] level4[],int index,int l2,int l3,int l4)when I call it with the following statement,
level1.process_l1_queue(process_count, level1,level2,level3,level4,l1ptr, l2ptr, l3ptr,l4ptr);
I get a cannot resolve symbol error pointing at the comma after l3ptr.
I've deleted the l4ptr and the same error points to the ).

wow. People can often be a bit too inflammatory with their replies here, but, at the risk of sounding like so, I would fire you on the spot if you develop an application class with that signature. There is no defense for such a signature- put some of those arguments in the constructor (this instance will always be of a certain calendar type, dollar currency), subclass- divide the functionality into smaller units. That signature is too complex and it will make every thing more difficult, particularly if some one else has to manage the code in the future. I would say, as a general rule, if you find yourself asking, will java let me put some thing this mammoth in it the way I intend, you're often using a poor design. All things being equal, you shouldn't normally have to test the limits of the JLS.

Passing final referance as argument to a method

Hi All,
I was wondering what is the benifit of declering a referance type in a method parameter as fianl.say
public void foo(final Point p)
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}also does this make any big differance .
public void foo(final Point p)
     this.p = new Point(p);
}

Hi All,
I was wondering what is the benifit of declering a
referance type in a method parameter as fianl.say
public void foo(final Point p)
     this.p = p;
Some people do that to avoid assignement to the argument by mistake.
E.g p = p;
>
also does this make any big differance .
public void foo(final Point p)
     this.p = new Point(p);
Not a big difference but it makes it impossible for others to manipulate your copy of the data. (If the constructor for Point is correctly implemented)
Kaj

Reflection in Numbers and Primitive Arguments in a Method

Hi ,
I am trying to invoke a method which has primitive or Number arguments, my problem is that when i do method.invoke( ) it gives an instantiation exception, because it was trying to do clazzT.newInstance( ) where clazzT happened to be int.class ... ? so how do i create a new Instance of such a primitive to add it to argument list while doing method.invoke ?
so what i mean is, have a method like :
public void doSomething(int x){
}and i am trying to do a method.invoke( ) in a for loop with all the methods of the classes ...
anyone!? please i am trying to figure this out for a while!? :)
Rick

public class AnnotationFinderLogger implements InvocationHandler{
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      * @param clazz
      * @throws Throwable
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               return;
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               T t = clazz.newInstance();
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               createProxy(t);
               Method[] methods = clazz.getMethods();
               for(Method method : methods){
                    if(method.getAnnotation(Log.class) != null && Modifier.isPublic(method.getModifiers())){
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                         // adds to the list of parameters by invoking clazz.newInstance( ) to gain the Object
                         List<Object> tempList = inspectParameterTypes(method);
                         args = tempList.toArray();
                         this.invoke(t, method, args);
      * @param <T>
      * @param t
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      * @param method
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}here's my proxy code. I am checking for @Log annotation and then invoking the methods, when i invoke the methods i have to pass in the argument types, in that case i would need to check if its a primitive or not etc ...
I am kinda lost now ... x_x
Regards
Vyas, Anirudh

Create an object with the name passed in as a string argument to a method

Hi,
I am sorry if it's too trivial for this forum , but I am stuck with the following requirements.
I have a method
void abc(String object_name, String key, String value)
method abc should first check if there exists in memory a hashmap object with the name passed in as argument object_name.
If yes ..just put the key and value there.
if not , then create the hashmap object called <object_name> and insert the key/value there.
Can anybody help me in the first step i.e, how to check if an object exists with the name passed in and if not then create it.
Will getInstance method be of any help?
Thanks in advance for your response.
-Sub-java

Dear Cotton.m,
Thanks for your suggesstion. I will remember that.
But somehow I have a strong belief that you still need to consult dictionary for exact meaning of the words like "upset" , "frustration" etc. Not knowing something in a language , that too as a beginner, does not yield frustration, but increases curiosity. And people like petes1234 are there to diminish that appetite.
To clarify above, let me compare jverd's reply to my doubt with petes1234's.
jverd said it cannot be done and suggested a work around (It was perfect and worked for me) While petes1234 , having no work in hand probably, started analysis of newbies mistakes.
jverd solved my problem by saying that it cannot be done. petes1234 acted as a worthless critic in my opinion and now joined cotton.m.
Finally, this is a java forum and I do not want to discuss human characteristics here for sure.
My apologies if I had a wrong concept or if I chose a wrong forum to ask, where people like petes1234 or Cotton.m show their geekdom by pointing out "shortfalls" rather than clearing that by perfect examples and words.
Again take it easy and Cotton.m , please do not use this forum to figure out others' frustration but be a little more focussed on solving others "Java related" problems :)
-Sub-java

Generic arguments in a Method on an interface.

Hi all,
I'm having trouble with the following code:
Basically this is what i want:
the Classes:
public class SuperClass
public class ClassA extends SuperClass
public class ClassB extends SuperClass
public class ClassC extends SuperClass
The interface
public interface interfaceX
   public methodX(SuperClass A);
Implementation of the interface
public class classX implements interfaceX
     public methodX(ClassA A)
}My problem is on the declaration of the interface interfaceX in the class classX.
How can i do such thing?
I'm trying to avoid the "correct" declaration. this is:
public methodX(SuperClass A)
        { ... }because I have a couple of class that extends that interface with deferents arguments, all of them extending from the SuperClass.
I know i could use the instanceof keywork, but i'm trying to avoid the extra checking...
Thanks in advance for any help!!
Edited by: ValdemarP on Mar 29, 2010 1:55 AM

i know I'm changing the contract, but only the arguments. if you notice, the new arguments is child of class SuperClass... How can I do this? Declare an method in an interface that accepts an arguments of some class and implement that interface, with argument that are children of the arguments declared in the interface... hope i was more clear this time... :(
Example. I can do this on an interface:
public void MethodListGeneric(List<? extends SuperClass> xpto )and during the implementation of the interface, I can declare the method using any arguments for the generic list, that extends SuperClass.
Example:
public class xpto extends InterfaceX
    public void MethodListGeneric(List<ClassA> xpto )
     // in here I've use ClassA insted of SuperClass
}Edited by: ValdemarP on Mar 29, 2010 3:15 AM
Edited by: ValdemarP on Mar 29, 2010 3:15 AM

Trying to pass arguments into a method call and failing

Hi everyone, I'm fairly new to programming, and newer to Java. I'm currently working on a project that pulls fields from a database based on a name, and I'm having some trouble getting the connection string set up.
Statically defined, the database connects and the program logic that follows works just fine. The problem is that to future-proof this application, I need to pass the database URL, port, db instance, username, and password into the program as arguments from the batch file that will then be scheduled to run the program on a job-by-job basis.
Product Version: NetBeans IDE 6.1 (Build 200805300101)
Java: 1.6.0_06; Java HotSpot(TM) Client VM 10.0-b22
System: Windows XP version 5.1 running on x86; Cp1252; en_US (nb)
Userdir: C:\Documents and Settings\xxxxxxxxxxx.SPROPANE\.netbeans\6.1
Here's my current working source (with the network addresses obfuscated):
package processsqrjob;
import java.io.*;
import java.sql.*;
import java.util.Date;
public class Main {
     * @param args jobname, jobparameters, HYPusername, HYPpassword, HYPservername, HYPport, oracleDBURL, oracleport (default 1512), SID (dbb?), oracleusername, oraclepass
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    public static void main(String[] args) throws SQLException
        DriverManager.registerDriver (new oracle.jdbc.driver.OracleDriver());
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        Statement stmt = con.createStatement();
        Date date = new Date(); //get the system date for output to both the error log and the DB's lastrun field
        System.out.println(date); //print the date out to the console
        System.out.println(args[0]); //print the job name to the console
        String sourcefolder=""; //we're going to load the job source folder into this variable based on the job's name
        String destfolder="";//same with this variable, except it's going to get the destination folder
        try {
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            while ( rs.next() ) {
                sourcefolder = rs.getString("sourcefolder");
                destfolder = rs.getString("destfolder");
            stmt.executeQuery("UPDATE myschema.jobs SET lastrun ='"+date+"' WHERE name ='"+args[0]+"'");//put this after hyp code
//            System.out.println(sourcefolder);
//            System.out.println(destfolder);
//            System.out.println(description);
            stmt.close(); //close up the socket to prevent leaks
        }catch(SQLException ex){
            System.err.println("SQLException: " + ex.getMessage());
            logError(args[0], ex.getMessage());
}That works, and it connects to the database and everything. But when I pass the variables in from the project properties run settings, I get the following exception:
Exception in thread "main" java.sql.SQLException: invalid arguments in call
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:111)
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:145)
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:207)
        at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:235)
        at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:440)
        at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:164)
        at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:34)
        at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:752)
        at java.sql.DriverManager.getConnection(DriverManager.java:582)
        at java.sql.DriverManager.getConnection(DriverManager.java:207)
        at processsqrjob.Main.main(Main.java:42)
Java Result: 1That is with Connection con = DriverManager.getConnection("jdbc:oracle:thin:@oracleserver.local.intranet.com:1521:dbname", "username", "pass"); changed to Connection con = DriverManager.getConnection("jdbc:oracle:thin:@"+args[6]+":"+args[7]+":"+args[8]+"\", \""+args[9]+"\", \""+args[10]+"\"");{code}, with args 6 7 8 and 9 set to url, port, dbinstance, username, and password respectively.
Perhaps it's the way I'm escaping the quotation marks, but I put that same line inside a System.out.println() and it output it exactly as I had typed it in statically before, so I don't know what it could be.
I would really appreciate any advice. Thanks in advance for your time.

I think you're mixing up SQL and Java. The Java method expects the user name and password as separate parameters, not encoded in one String. So you shouldn't be concatenating args[9] and args[10] at all, they should remain as separate parameters.
The call should be:DriverManager.getConnection("jdbc:oracle:thin:@" + args[6] + ":"+ args[7] + ":" + args[8], args[9], args[10]);
                                                 parameter 1                                  2         3

Passing arguments to a method

I need to pass an ip address into a method. So I know its type InetAddress. If the IPAddress is 10.100.50.33. how would I pass it in to the method. eg:
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SysNameScanCommand(InetAddress 10.100.50.33 )

It depends what kind of argument your function is expecting. If it wants a String, you could call
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SysNameScanCommand(new InternetAddress("10.100.50.33"));

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Problem:
A COM’s object method is expected to receive two
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According to CFMX documentation, you pass variables ‘by
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types, but not for objects.
Any idea how to pass an object by reference?

Would it help to convert it to a string while passing between Python and LabVIEW?
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I have somewhat of a problem. I'm trying to create a method, stringQuery, and I do not know how many arguments the method will take.
Allow me to explain my goal, so you can have some idea of what I'm talking about.
I want to create a method that will basically generate a SQL query (no, this is NOT a JDBC question) from text. This method should be able to take a large number of String arguments, because the user might want to select one thing from the database, or he or she might want to select five things, or he or she might want to select twenty things.
Because of this, there is not a set number of arguments for my stringQuery method.
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Also, please let me know if this didn't make much sense, and what part of it didn't make sense.
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Dan

I'm not too sure what you mean by this. Do you know
of any links or resources that can explain this
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Leo

I'd like to add the the webservice being invoked by the generated client stubs is rpc/encoded.

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Final Cut Studio Crossgrade - Best method for upgrade?

Hi,
I've received my new Final Cut Studio crossgrade disks after surrendering my old ones to Apple and paying my £40 plus p&p (seems a bit antiquated doesn't it) and now I'm wondering how to go about installing.
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I would appreciate advice from anyone who has tried their method and is certain it definitely works!
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Final as argument to a method....

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