In terms of scalabilty, will static method in normal java class better than

You only have one copy of the static method in memory, but you have a few copy of the stateless session bean, plus the overhead of those session bean.So isn't static method of normal java class more scalable than stateless session bean.

Then you have to take care of transaction management, connection pooling, etc other ejb services all by your self.
In fact stateless session beans acts more like a static class. They do not get destroyed when remove() method is called on client stub. Similarly they are not always gets created whenever someone calls create() method on home interface!! (Again it's specific to appserver implementation)
Thx.

Similar Messages

Can we call a static method without mentioning the class name

public class Stuff {
 public static final int MY_CONSTANT = 5;
 public static int doStuff(int x){ return (x++)*x;}
import xcom.Stuff.*;
import java.lang.System.out;
class User {
 public static void main(String[] args){
 new User().go();
 void go(){out.println(doStuff(MY_CONSTANT));}
}Will the above code compile?
can be call a static method without mentioning the class name?

Yes, why do it simply?
pksingh79 wrote:
call a static method without mentioning the class name?For a given value of "without mentioning the class name".
 public static Object invokeStaticMethod(String className, String methodName, Object[] args) throws Exception {
 Class<?>[] types = new Class<?>[args.length];
 for(int i=0;i<args.length;++i) types[i] = args==null?Object.class:args[i].getClass();
return Class.forName(className).getDeclaredMethod(methodName,types).invoke(null,args);

Access DataControls methods in a java class

Hi All,
Jdeveloper Version 11.1.5
I have created DataControls for SessionFacade web service.
Inside the datacontrol there is a method getAllDepartments() which have a Return type which includes DaertmentId,DepartmentName,....
I want to know how can i access this method inside a Java Class and create a list of only departmentId.

You would need to add the method in the data control as a method action in your pageDef.
After that, you could access the method as mentioned above.
Thanks,
Navaneeth

Generic static methods in a parameterized class

Is there anything wrong with using generic static methods inside of a parameterized class? If not, is there anything special about defining them or calling them? I have a parameterized class for which I'd like to provide a factory method, but I'm running into a problem demonstrated below:
class MyClass<T> {
 private T thing;
 public
 MyClass(T thing) {
 this.thing = thing;
 public static MyClass
 factoryMakeMyClass(U thing) {
 return new MyClass(thing);
class External {
 public static MyClass
 factoryMakeMyClass(U thing) {
 return new MyClass(thing);
class Test {
 public static void
 test()
 // No problem with this line:
 MyClass<String> foo = External.factoryMakeMyClass("hi");
 // This line gives me an error:
 // Type mismatch: cannot convert from MyClass<Object> to MyClass<String>
 MyClass<String> bar = MyClass.factoryMakeMyClass("hi");
}Does this code look ok to you? Is it just a problem with my ide (Eclipse 3.1M2)? Any ideas to make it work better?

I've been working on essentially the same problem, also with eclipse 3.1M2. A small variation on using the external class is to use a parameterized static inner class. I'm new enough to generics to not make definitive statements but it seems to me that the compiler is not making the correct type inference.
I think the correct (or at least a more explicit) way of invoking your method would be:
MyClass<String> bar = MyClass.<String>factoryMakeMyClass("hi");
See http://www.langer.camelot.de/GenericsFAQ/FAQSections/TechnicalDetails.html#FAQ401
See http://www.langer.camelot.de/GenericsFAQ/FAQSections/TechnicalDetails.html#FAQ402
Unfortunately, this does not solve the problem in my code. The compiler reports the following error: The method myMethod of raw type MyClass is no more generic; it cannot be parameterized with arguments <T>.
Note that in my code MyClass is most definitely parameterized so the error message is puzzling.
I would like to hear from more people on whether the sample code should definitely work so I would appreciate further comments on whether this an eclipse problem or my (our) misunderstanding of generics.

Static methods in data access classes

Are we getting any advantage by keeping functions of DAOs (to be accessed by Session Beans) static ?

I prefer to have a class of static methods that
require a Connection to do their work. Usually, there
is a SessionBean that 'wraps' this DAO. The method
signatures for the SSB are the same, minus the need
for a Connection, which the SSB gets before delegating
to the Static Class.Uggh, passing around a connection. I've had to refactor a bunch of code that used this pattern. We had classes in our system that took a class in their constructor simply because one of their methods created an object that needed the connection. Bad news--maintenance nightmare--highly inflexible.
What we've done is create ConnectionFactory singletons that are used throughtout the application in order to get connections to the database. All connection factory implementations implement the same interface so they can be plugged in from other components at runtime.
In my opinion, classes that use connections should manage them themselves to ensure proper cleanup and consistent state. By using a factory implementation, we simply provide the DAO classes the means by which they can retrieve connections to the database and even the name of the database that needs to be used that is pluggable. The DAO classes do their own connection management.
For similar reasons, I eschew the static method concept. By using class methods, you make it difficult to plug in a new implementation at runtime. I much prefer the singleton pattern with an instance that implements a common interface instead of a class full of static methods.
I recently needed to dynamically plug in new connection factory implementation so that we could use JNDI and DataSources within the context of the application server (pooled connections) but use direct connections via the Driver manager for unit testing (so the application server didn't need to be running). Because of the way this was coded, I simply changed the original factory to be an abstract factory and changed the getInstance() method to return a different implementation based on the environment (unit test vs live). This was painless and didn't require changing a single line of client code.
If I had to do this using the previous code that I refactored, I would have had to change about 200 jsp pages and dozens of classes that were making calls to the static method of the previous factory or hacked in something ugly and hard to maintain.
YMMV

Invoking a method from a java class to a jsp file

Maybe i'm going through a very basic error, but as i've looked for in some forums and nothing found decided to post. So let's go to the problem.
Well, i have a form in a jsp file, it's basicaly html, but as i need some select boxes populated with data from the database i decided to create some methods in java classes. This is the point.
My method receive some attributes, like the table and colums names, the name of the select box and the HttpServletResponse object.
So after making all the database process. The method is supposed to write the result through the out.println(); object
It goes everything all right except that the method seems to be called first than the html code coz' my select boxes comes above the head in the begin of the page and was supposed to come in the middle.
part of the code:
package pacote;
import java.packages.*
public class Class{
public void metodo(HttpServletResponse response, String tableName, String column name, String selectName){
PrintWriter out = response.getWriter();
openConnection();
//After making the query stuff
//caso n�o haja nada na consulta
 if(rst == null)
 out.println("N�o h� registros.");
 else{
 out.println( "<select name='" +SelectName + "' id='" +SelectName + "' class=\"input_ob\" >");
 out.println( "<option value=''>Escolha: "+objeto+"</option>");
 //fill the select body with options; A while that sweap the resultSet and use the out object to write the results
 getSelectBody(out,rst, selectValue);
}This method is called this way:
<tr valign="baseline">
 <td nowrap align="right">Grupo</td>
 <jsp:useBean id="m" scope="page" class="pacote.Class" />
 <td>
 <%
 try{
 m.metodo(response, "tabela","grupo","id_grupo);
 } catch (IOException e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
 %></td>I'd like to know what i'm missing here. why the answer doesn't go in the place It's supposed to go.
any answer will be greatly apreciated

The issue is caused because you are using the response to get the writer directly.
The JSP has gotten the same writer, but has wrapped it in a JSPWriter class. That class has got a buffer.
So it writes the beginning html to the JSPWriter buffer.
You write your stuff to the response writer - gets sent to the output.
It writes more stuff to the JSPWriter buffer, then flushes that buffer - at which point all the text written into the JSP writer now gets added to the response.
You see how your code is coming out first?
Solution - instead of getting the writer from the response, pass the writer into your method (maybe instead of response if you don't use response for anything else)
public void metodo(Writer jspWriter, String tableName, String column name, String selectName){
PrintWriter out = new PrintWriter(jspWriter);
...That means that you will be writing to the same writer, and the text should come out in sequence.
Cheers,
evnafets

Synchronized method in a java class used by many interfaces

My interface (idoc to file) is using a java class, which has one method that reads a table from a central database and after doing some calculations updates it.
(The interface instantiate the class inside a user-defined function and calls the method there.)
The problem is that if somebody sends 100 idocs at the same time, there can be a dirty read, I mean, a read just before other interface updates the table.
We want the following:
Interface 1:
- Read counter from the table (counter = 5 )
- Increment counter (counter = 6)
- Update table with that counter (table with counter = 6)
Interface 2:
- Read counter from the table (counter = 6 )
- Increment counter (counter = 7)
- Update table with that counter (table with counter = 7)
RESULT: The table has the counter = 7
But what is happening is the following:
- Interface 1 reads (counter = 5)
- Interface 2 reads (counter = 5)
- Interface 1 increments counter (counter = 6)
- Interface 2 increments counter (counter = 6)
- Interface 1 updates table (table with counter = 6)
- Interface 2 updates table (table with counter = 6)
RESULT: The table has the counter = 6 (WRONG)
I made the method synchronized. What I was expecting was that only one interface (i1) could enter the method (read the table and update it) while other interfaces running at the same time would have to wait until i1 finished that method.
My first test indicates that's not happening. Can anybody help me to find a solution?

Hi Bhavesh,
If the QOS is EOIO this means that the integration engine manage the call to the mapping program (and all the other blocks) inside an "internal" synchronized method.
So this means that in this case you do not need to manage the queued access (synchronization) inside your custom java code because it is already enveloped in a queued block by XI.
The problem that Jorge had can be easily reproduced using the sample code that follows:
class Synch Object
import java.util.Date;
public class SynchObject {
 String strName;
 public SynchObject(String strName){
 this.strName = strName;
 public synchronized void syncWrite(String strCaller) throws InterruptedException{
 Date now;
 now = new Date();
 System.out.println("-- " + now.toLocaleString() + " " + strCaller + " entering syncWrite of " + strName);
 System.out.flush();
 Thread.sleep(1000);
 now = new Date();
 System.out.println("-- " + now.toLocaleString() + " syncWrite of " + strName + " called by " + strCaller );
 System.out.flush();
 Thread.sleep(1000);
 now = new Date();
 System.out.println("-- " + now.toLocaleString() + " " + strCaller + " leaving syncWrite of " + strName);
 System.out.println("");
 System.out.flush();
class Caller
public class Caller implements Runnable {
 String strName;
 SynchObject target;
 int intMax;
 public Caller(String strName, SynchObject target, int intMax) {
 this.strName = strName;
 this.target = target;
 this.intMax = intMax;
 public void run() {
 for(int i=0; i<intMax;i++)
 try {
 target.syncWrite(strName);
 } catch (InterruptedException e) {
 e.printStackTrace();
class Workbench
public class Workbench {
 public static void main(String[] args) {
 // TODO Auto-generated method stub
 SynchObject sObj1 = new SynchObject("syncObj1");
 SynchObject sObj2 = new SynchObject("syncObj2");
 Caller c1 = new Caller("caller1",sObj1,2);
 Caller c2 = new Caller("caller2",sObj1,2); '[*CHANGE*]
 Thread ct1 = new Thread(c1);
 Thread ct2 = new Thread(c2);
 ct1.start();
 ct2.start();
Run the workbench class to see what happen when setting QOS EOIO (the synch object is the same).
To see instead what happen now (missing synchronization) you have to change in Workbench class the statement
Caller c2 = new Caller("caller2",sObj1,2); '[*CHANGE*]
with
Caller c2 = new Caller("caller2",sObj2,2); '[*CHANGE*]
The reason is that every instance of the mapping program declare a new instance of the "Synchronized object" so the calls are synchronized inside the same mapping program but not between several mapping program.
Hope this give you a better idea on this problems with java synchronization, but if you have further doubts (I know it's a little bit tricky ) feel free to ask.
Kind Regards,
Sergio

Calling a static method when starting the server???

Hi,
i wanted to call a static method of a java class,
whenever i start the server.
plz give some input on this.
thanks and regards
siva

Siva -- Can you be more specific as to the problem you are trying to solve (why do you want to call this static method,.)
The reason I ask is that there are some ways to make this happen but they may have limitations
that won't work for you. For instance, you can create a servlet that calls your class' static method and then make the
servlet be loaded on startup.
Thanks -- Jeff

Can't get ClassLoader from static method.

I'm trying to get the ClassLoader within a static method getInstance().
public class PropertyManager {
public static PropertyManager getInstance(String fileName) {
//The following line returns null
ClassLoader cl = (new Object()).getClass().getClassLoader();
URL url = cl.getResource(fileName);
etc...
However if getInstance gets called from e.g. a statless session bean, a null
is returned instead of a valid ClassLoader.
The same code executed from a standalone java program (e.g. from
main(String[] args)) returns a valid ClassLoader
Why does getClassLoader behave differently in WebLogic than in a standalone
java program?
Thanks for you help.
Bernie

Sorry for the confusion. I wrote a couple of more test programs and was able
to confirm that WL behaves exacltly the same as java does. For some reason
my intial tests were messed up...
getClassLoader() executed from a static method always returns null (in WL as
well as in a java standalone program).
In this case ClassLoader.getSystemClassLoader() will return a valid class
loader.
Thanks for your help.
Bernie
"Rob Woollen" <[email protected]> wrote in message
news:[email protected]..
Bernhard Lenz wrote:
I tried that as well, but getClassLoader() still returns null when
executed
in WL.
I'm still not clear how getClassLoader() gets affected by running withinWL.
>>
>
Very odd. Where is this class located? in the server's classpath, in ajar or
war file? Does getClass().getClassLoader work from a non-static method inthis
class?
-- Rob
"Rob Woollen" <[email protected]> wrote in message
news:[email protected]..
You want PropertyManager.class.getClassLoader()
-- Rob
Bernhard Lenz wrote:
I'm trying to get the ClassLoader within a static method
getInstance().
>>>>
public class PropertyManager {
public static PropertyManager getInstance(String fileName) {
//The following line returns null
ClassLoader cl = (new Object()).getClass().getClassLoader();
URL url = cl.getResource(fileName);
etc...
However if getInstance gets called from e.g. a statless sessionbean, a
null
is returned instead of a valid ClassLoader.
The same code executed from a standalone java program (e.g. from
main(String[] args)) returns a valid ClassLoader
Why does getClassLoader behave differently in WebLogic than in astandalone
java program?
Thanks for you help.
Bernie

OOPs Concept ! - Why Static Methods can't be redefined in its subclass ?

Dear Experts ,
I had searched the SDN , but unable to find out the satisfactorily answers ..
Can anybody let me know the reason for the following Confusion in Oops Concept
Question 1: As we know , We can Inherit the Static Methods in the Sub Class , But we can't redefine it in the base class or Sub Class ?
Question 2 : Why can't Static Method be Abstract ?
Question 3 : Can a Class be Abstract or Final Both, If yes, then why ?
Thanks in Advance
Saurabh Goel

As per the above discussion two of your doubts have already been clarified so I am taking only third one.
A class cannot never be Abstract and final both coz Abstract signifies that the implementation of the class has not been defined completelyi.e. may be some methods have been defined but few methods are still missing implementation. 'Final' is used for those classes/methods which cannot be redefined means the complete implementation of the method has been defined no one can implement further logic under the same method.
If you are saying your method is Final then it cannot be overridden and Abstract implies that method implementation is yet to be defined which can only be implemented if that class/method is not 'Final'. So both the terms are contradictory.
Hope it clarifies!!!
Thanks,
Vishesh

Drawbacks of static methods?

What's the better approach for utility methods:
a) write abstract class with static methods
b) write class with non-static methods and instantiate this class to call the public methods.
?

What's the better approach for utility methods:Define "utility methods".
a) write abstract class with static methodsProbably not - surely a final class would be better than an abstract one?
b) write class with non-static methods and instantiate
this class to call the public methods.Do you (or might you ever) want to be able to plug in different implementations? If so, then this is the better option. If not, then a final class with all methods static will probably do the job very well.

Abstract static methods

Hello,
I've written an abstract class, called AbstractNetworkParticipant. I've also written two sub classes that extend this class. I'm in the process of writing a Viewer class that I'm intending to parameterized with some subclass of AbstractNetworkParticipant,
public class Viewer<T extends AbstractNetworkParticipant> I would like to include a couple of static methods that return Strings for Labeling information to a particular subclass in the Viewer.
So for example, if I have NetworkUser and NetworkAdministrator, both of which extend AbstractNetworkParticipant, I would like to set the text of a JLabel labeling the participant's name to "User Name", or "Administrator Name" depending on the type of participant being viewed.
I would like the method that returns these strings to be static, so that I don't have to have an instance of the current subclass when I initializes the JLabel. An abstract method cannot be static. I attempted to make a non-abstract static method in the abstract class,
public static getDescriptor() {
 return "Participant";
}and then override it in each sub class to a more descriptive string (User, or Administrator). However, when I reference the method, it always invokes the method defined in the abstract parent class, rather than in the subclass, whichever it may be.
Can anyone suggest a solution. Should I just forget about the method being static? Is there a better way to implement a solution to this problem?
Thanks
Edited by: paulwooten on Mar 27, 2009 9:58 AM

paulwooten wrote:
The whole point of my original post was in order to learn something about Java that I'm not particularly familiar with. I was having a difficult time articulating the problem precisely, so I tried to draw an analogy between C++ and Java. It turns out I was mistaken in the way C++ works. Fortunately I described my problem adequately enough to both 1. be corrected about how virtual functions actually work in C++, and 2. get advice on how to approach the problem in Java. I never claimed I was a C++ expert, or that I was asking a question about C++. I was just trying to explain my problem as precisely as possible.
I don't mean to disrespect, but your post, and slimy's aren't nearly as constructive as all the other posts that actually addressed my question; either to me personally, or to anyone else who has a similar question and may happen to read this thread. It's not like I dumped a bunch of C++ code here and begged someone to translate it for me. I asked a question, to the best of my ability, several other forum members replied (without giving me a mini lecture on how to learn Java), and now the problem is resolved.Sorry for the confusion. I wasn't complaining about your post. My post wasn't directed at you at all. It's fine to know C++, and to ask how to do something similar in Java. As you said, that wasn't even how you asked your original question. You asked a legitimate question to learn Java, a few people made suggestions, you made a comparison to C++, and people corrected your understanding both of C++ and Java. That's all well and good, and it's a fair way to learn. I see no problem with any of that.
What exactly does "learn Java properly" mean? Read the tutorials and pretend like no other programming languages exist?I was referring to slimy's post where he talked about "knowing C++ properly if you use it as an input to Java". The point of my post was supposed to be that "you can know C++ properly, but +you shouldn't always use that as your input to Java+". A very simple example I've seen of what I meant by "non-proper" Java code, in real [but +bad+ ] Java code at a real company is for String comparison:
String abc = "abc";
String xyz = "xyz";
String another = "xyz";
if (abc.compareTo(xyz) != 0) { // Not "proper" Java
 doSomething();
if (xyz.compareTo(another) == 0) { // Not "proper" Java
 doSomethingElse()
}To me, that looks like someone who copied their C++ knowledge (or, at least, C knowledge) to the extreme. In C, the only function to test equality of two C "strings"--i.e., "null-terminated char arrays" is 'strcmp', and you test equality of the strcmp result to 0 to determine whether two "null-terminated char arrays" represent the same thing:
char abc [] = "abc";
char xyz [] = "xyz";
char another [] = "xyz";
if (strcmp(abc, xyz)) { // could include explicit != 0, but not needed in C
 doSomething();
if (!strcmp(xyz, another)) { // anything non-zero is true in C, so !0 is true
 doSomethingElse();
}"compareTo" sounds like "strcmp", and the comparison to 0 is the same in my above examples.
But, in Java, there is a real "equals" method for Strings, and it should be used:
String abc = "abc";
String xyz = "xyz";
String another = "xyz";
if (!abc.equals(xyz)) { // "proper" Java
 doSomething();
if (xyz.equals(another)) { // "proper" Java
 doSomethingElse()
}I would argue that using "compareTo" to test equality of Strings in Java is "non-proper" Java, and using "equals" to test equality of Strings in Java is "proper" Java. That was my definition of "learning Java properly".
I certainly don't think anyone learning Java needs to pretend that no other programming languages exist--it is fine to know other languages, and to look for the similarities (and differences). However, someone learning Java (or any other language new to them) does need to know that things don't work the same in all languages, so, if they base all of their knowledge by trying to get Java to work exactly the same as C++ (or whatever previous language they knew), their Java will not be "proper" Java. There are often multiple ways to do things "properly" in Java, but copying a C++ program verbatim into Java syntax is not necessarily going to result in the best Java code that you could have. When doing the translation from another language to Java (I realize that isn't your goal, but for some people, that is the goal), you need to be sure that your Java code follows Java rules and standards, and not just assume that the architecture of your Java code should be the same as the architecture of your code in the original language.
I hope that clarifies my intentions. As I said, I wasn't directing my previous comment to you. I think your question and learning approach are absolutely fine.

Static methods in multi-threaded environment

Hi,
I am wondering what happens when several threads try to access the same static method ?
The static method is not synchronized.
Will this create any performance issues ?
The actual scenario is of a J2EE server, where several Session Bean instances try to access a static method in a utility class. Will some session beans have to wait till others are being serviced ?
thnx n regards
s giri

thanx for replying.
yes. the operations are thread-safe. we do not change the state of any object.
but we make an rmi call to another application thru this static method.
is it ok?
Currently, my session bean has too many private methods - each calling the other application. Due to some quality metrics (a class must be restricted to 700 lines) we have to consider moving these private methods into some Helper class in the form of "public static methods". We have made many utility methods as static, but have some reservations abt doing a similar thing for these methods that call other application.
regards
Shivraman

Static methods in encoded XML output stream

I have a class designed to be instantiated, then initialized in several steps, one of them being the use of a static method declared in a separate class. The approach works fine in a Java program but when I attempt to devise a persistence delegate to handle the XML encoding of those steps, XMLEncoder objects to the use of a Statement object specifying a method that is not a member of the class being encoded. It keeps looking for the method in the target class and, not finding it, posts a failure.
The persistence delegate exists in a separate module being designed to support serialization of classes in the target package. I can do a workaround by inserting a member method in the target class to wrap the static method in the other class but for reasons of coding economy prefer not to do that. And it seems to me this defeats the purpose of the persistence delegate. I want to design the persistence support module to fit the target package, not the other way around.
Is it possible to encode a Statement object to invoke a separately-defined static method? If so, how do I code it?

I'm trying to produce a statement instantiated as:
*Statement stmt = new Statement(oldInstance, "myMethod", new Object[]{arguments});*
where oldInstance is the instance of targetClass being persisted and myMethod is the name of a utility static method in a separate class that performs certain initializations. Next line is
out.writeStmt(stmt)
where out is the Encoder instance passed in to the initialize method of the persistence delegate. Encoder expects to find myMethod as a member of targetClass. When it doesn't it issues a message of the form:
java.lang.Exception: Encoder: discarding statement targetClass.myMethod( arguments );
The Javadoc description for Encoder.writeStatement confirms this, that the statement
"... should be written entirely in terms of the callers environment ..."
The Encoder doesn't have the other class in context at this point in the object graph being written and evidently isn't endowed with the ability to look outside of that context. If, instead of oldInstance in the Statement construction I put something like OtherClass.class, the result is that Encoder doesn't complain but simply ignores the statement and generates no output for it.
Without going into discussion of why the target class and the utility method are designed like this, let me just say they are based on prudent design considerations and work well. I was hoping to write a persistence delegate without contorting the target class but thus far haven't found a way.

Can you override a public static method?

Can you override a public static method?

A static method belongs to a class, not to a particular object, because you can call them without having an object instantiated. Methods are over rided which are inherited from an object. Since Static methods (although inherited) are not bound to a particular object, are not overridden.
Though you have a method in the subclass with the same signatures but if you try to call super.____() you will get the error
non-static variable super cannot be referenced from a static context

In terms of scalabilty, will static method in normal java class better than

Similar Messages

Maybe you are looking for