Is static constructors exist in java or not?

Hi,
I would like to know the existence of static constructors in java.
If yes... reason
If no... reason
Can anyone throw some light on this topic.......?

This question hardly makes sense. A constructor isn't even a proper
method, i.e. it can only be called by the 'new' operator. In a way you
can consider ctors being static because you don't need an object to
invoke it on.
kind regards,
Jos

Similar Messages

Anyone heard of static Constructor? Pure Concept Question

Hi All,
I guess this is a little obscure but let me ask this anyway.
Has anyone heard about a "static constructor"? No I am not talking about a static block in your code. I am talking about a static method which will be called every time you make a static call on a particular class. Just like the constructor gets called every time you create an Object. The difference will be that the static code will be executed only once while the static constructor will be called every time you call a static method.
My question: Do you see a need, from the experience you have got, about such a construct being a feature of a language? I was talking to some people of a very well known company - who were telling me about this special feature - as they put it - being part of their Proprietary language. They couldn't convince me as to why this "special" feature was required. I seek help from the Community to help me think about this. I tried seeking an answer to this question on the net but to no avail.
I for one, am not going to stop my quest after posting here - but I would be grateful if any of you could help me.
Thanks for all your support.
Best Regards,
Manish

Hi All,
I am overwhelmed by the response. Thanks for spending your time thinking about this.
Some of the questions you asked were...
teknologikl : Did the people say about how is it useful?
javax.pert : No. They tried to tell me things like initializing static objects which I could have as well done in a common method which I call in the start of every static method. Basically they could not convince me about the use of a static constructor. May be they did not know too well why it was put in the first place. Because I was talking to programmers rather than Designers. But I did not want to stop at that. I wanted to tickle my gray cells and yours to find out why would someone put this as part of a language? I agree with most of your posts but instead of telling me that this is not going to be very useful ( which I already thought of), I would appreciate if you can help me think Why would someone have put it at all. You see what I am saying?
rjwr: static factory methods
javax.pert: Yup. I am aware and use static factory methods. But this is a little different. This is called automatically by the VM - just like a normal constructor - whenever a static method is called.
dubwai: This sounds pretty lame to me...
javax.pert: Sorry if I wasted your time. But please look at my response to teknologikl above.
DrClap:
javax.pert: Yup, yup. I thought just the way you are saying. I am actually trying to get in touch with some one who knows more about this proprietary language - maybe one of the designers. I would be glad to share the findings when it comes - if it is worth sharing of course. Thanks for your time though. :)
rvflannery: Security framework.
javax.pert: True. I agree with you about this being a wrapper for security purposes. Maybe this is what they thought of. One reason I see is that because they expose the APIs to third party vendors. These APIs can talk, by extending certain objects, to the sensitive areas of the database. I guess this could be one of the reasons. I will share it once I know more about it.
trejkaz: For debugging.
javax.pert: See my answer to rvflannery above.
Thanks all of you for spending your time with me. I will keep you informed whenever I get something worth sharing.
Thanks again,
Best Regards,
Manish

Unable to lookup home: Path to object does not exist at : java:comp#

Hallo,
I do not understand why I am getting the exception:
Unable to lookup home: Path to object does not exist at : java:comp#
if i have defined in the ejb-j2ee-engine.xml the jndi name:
<enterprise-beans>
     <enterprise-bean>
          <ejb-name>MyConverterBean</ejb-name>
          <jndi-name>MyConverterBean</jndi-name>
          <session-props/>
     </enterprise-bean>
</enterprise-beans>
and in the ejb-jar.xml :
<enterprise-beans>
   <session>
      <description>the converter bean</description>
      <display-name>MyConverter</display-name>
      <ejb-name>MyConverterBean</ejb-name>
      <home>converter.MyConverterHome</home>
      <remote>converter.MyConverter</remote>
      <local-home>converter.MyConverterLocalHome</local-home>
      <local>converter.MyConverterLocal</local>
      <ejb-class>converter.MyConverterBean</ejb-class>
      <session-type>Stateless</session-type>
      <transaction-type>Container</transaction-type>
    </session>
</enterprise-beans>
I am creating the EJB in this way:
ic = new InitialContext();
objRef = ic.lookup("java:comp/env/ejb/MyConverter");
home = (MyConverterHome)PortableRemoteObject.narrow(objRef, MyConverterHome.class);
converter = home.create();
I checked in the Administrator tool under JDNI / ejbContext and I can see MyConverterBean in the list.
Do you have any idea what I am doing wrong?
thanks a lot for your help,
SAPLernen

Hi Vladimir,
do you have some example or tutorial of how can i implement java proxies from a java stand alone application.
i allready make everyting but i'm still having problem.
this line give me a null
queryOutLocalHome = (UsersSyncMI_PortTypeLocalHome)ctx.lookup("java:comp/env/ejb/UsersSyncMI_PortTypeBean");
this is my java class that invoke my ejb java proxy
package com.gsk.xi.demo;
import java.util.Properties;
import javax.naming.Context;
import javax.naming.InitialContext;
import com.sap.aii.proxy.xiruntime.core.MessageSpecifier;
public class InvokeProxy {
     private Object objRef = null;
     private InitialContext ic = null;
     public String getRole(String name, String pwd){
          String role="0";
          UsersSyncMI_PortTypeLocalHome queryOutLocalHome=null;
          UsersSyncMI_PortTypeLocal queryOutLocal=null;
          try{
               Context ctx = null;
               Object ref = null;
               Properties p = new Properties();
               p.put(Context.INITIAL_CONTEXT_FACTORY,"com.sap.engine.services.jndi.InitialContextFactoryImpl");
               p.put(Context.PROVIDER_URL, "buasapp012.gwamericas.corpnet1.com:50004");
               p.put(Context.SECURITY_PRINCIPAL, "J2EE_ADMIN");
               p.put(Context.SECURITY_CREDENTIALS, "was1234");
               ctx = new InitialContext();
               //objRef = ic.lookup("java:comp/env/ejb/UsersSyncMI_PortTypeBean");
               //queryOutLocalHome = (UsersSyncMI_PortTypeLocalHome)PortableRemoteObject.narrow(objRef, UsersSyncMI_PortTypeLocalHome.class);
               queryOutLocalHome = (UsersSyncMI_PortTypeLocalHome)ctx.lookup("java:comp/env/ejb/UsersSyncMI_PortTypeBean");
               queryOutLocal = queryOutLocalHome.create();
               MessageSpecifier msg = queryOutLocal.$messageSpecifier();
               msg.setSenderService("JAVA");
               queryOutLocal.$messageSpecifier(msg);
               UserDT_Type reqtype = new UserDT_Type();
               reqtype.setUsername(name);
               reqtype.setPassword(pwd);
               UsersDBMTResponse_Type response = new UsersDBMTResponse_Type();
               response = queryOutLocal.usersSyncMI(reqtype);
               role = role + response.getStatementResponse().getRow().getRole();
          catch(Exception ex){
               System.out.println(ex.getMessage());
          return role;
} //end of class
thanks for your time
Lionel

Why java does not force to declare atleast one abstract method

hi,
i can define an abstract class without declaring any abstract method in that class. But why wud i do this ? i mean when i have decided that a particular class should be inherited by other subclass and subclass should porvide implementation then there should be atleast one method in the abstract super class which requires implementation.
All i want to know is why java does not force to declare atleast one abstract method in abstract class.
there may be some situations where this restriction can create problem if it is like that then can anybody give some example.
manish

hi,
i didn't get u.
u r trying to say that i have an abstract class with
only static methods then my questions is why wud
declare such a class as 'abstract' class? because a
static method can't be abstract also. Even then if
somebody want to define such a class with only static
methods then compiler should force him to declare
atleast one abstract method which can be implemented
by subclass, because as i said before if sumbody
decide to define a class abstract then he wants that
it should be inhereted but as u r saying a class with
only static methods then it should not be an abstract
class it can be a simple class.there's no functional reason, really... actually, factory-like classes are often defined the way Ceci described
"abstract" only ensures that nobody can ever get an instance of that class (as a matter of fact, what would be the point of getting an instance, if no instance method exists ?)

"Java Class not found in classpath" Error in DESIGNER

Hello All,
I'm trying to connect in Designer using a JDBC connection to MS SQL Server 2008. As per the instructions, I updated my jdbc.sbo file with the path to the existing two JAR files. However, I still get the following error when I try and connect in Designer: "Java Class not found in classpath : C:\Program Files\Business Objects\BusinessObjects Enterprise 12.0\win32_x86\dataAccess\connectionServer\jdbc\Drivers\sqlsrv". Of course, this error includes the drive path with the location to my JAR files. Any help in resolving this nagging issue is very GREATLY appreciated. Also, if anyone needs it I can post a copy of the jdbc.sbo file to this thread.
Thank you,
Pankaj

Stratos,
Your suggestion didn't help. I tried to connect after restarting my machine and I still get the error. And, I've also tried adding a connection to MS SQL Server 2005 using this JDBC driver, and that didn't help either. Any other suggestions? Would it help to see my "jdbc.sbo" file? Thanks again for your and everyone else's help, and I look forward to your reply.
Regards,
Pankaj

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.

Java program not running by the Ant

i have a small java program.
its a classpath problem.
cant figure out where is the problem.
i am running the code via Ant.
build.xml
<?xml version="1.0"?>
<project name="myproject" basedir="." default="all">
    <property name="src.dir"     value="src"/>
     <property name="classes.dir" value="classes"/>
     <property name="lib.dir"     value="C:/tomcat/webapps/axis/WEB-INF/lib"/>
     <property name="runclass" value="TestClient"/>
     <target name="all" depends="clean,compile"/>
     <target name="clean">
        <delete dir="${classes.dir}"/>
    </target>
    <path id="classpath">
        <fileset dir="${lib.dir}" includes="**/*.jar"/>
    </path>
    <target name="compile">
        <mkdir dir="${classes.dir}"/>
     <javac srcdir="${src.dir}"
      destdir="${classes.dir}"
      deprecation="on"
      debug="on">
   <classpath><path refid="classpath"/></classpath>
</javac>
     </target>
     <target name="run" depends="compile">
   
   <java classname="${runclass}">
        <classpath>
          <pathelement path="${classpath}"/>
          <fileset dir="${lib.dir}">
            <include name="**/*.jar"/>
        </fileset>
          </classpath>
       </java>
</target>
     </project>i invoked
ant runand got this
Buildfile: build.xml
compile:
run:
     [java] Could not find TestClient. Make sure you have it in your classpath
     [java]     at org.apache.tools.ant.taskdefs.ExecuteJava.execute(ExecuteJava
.java:170)
     [java]     at org.apache.tools.ant.taskdefs.Java.run(Java.java:710)
     [java]     at org.apache.tools.ant.taskdefs.Java.executeJava(Java.java:178)
     [java]     at org.apache.tools.ant.taskdefs.Java.execute(Java.java:84)
     [java]     at org.apache.tools.ant.UnknownElement.execute(UnknownElement.ja
va:275)
     [java]     at org.apache.tools.ant.Task.perform(Task.java:364)
     [java]     at org.apache.tools.ant.Target.execute(Target.java:341)
     [java]     at org.apache.tools.ant.Target.performTasks(Target.java:369)
     [java]     at org.apache.tools.ant.Project.executeSortedTargets(Project.jav
a:1216)
     [java]     at org.apache.tools.ant.Project.executeTarget(Project.java:1185)
     [java]     at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(De
faultExecutor.java:40)
     [java]     at org.apache.tools.ant.Project.executeTargets(Project.java:1068
     [java]     at org.apache.tools.ant.Main.runBuild(Main.java:668)
     [java]     at org.apache.tools.ant.Main.startAnt(Main.java:187)
     [java]     at org.apache.tools.ant.launch.Launcher.run(Launcher.java:246)
     [java]     at org.apache.tools.ant.launch.Launcher.main(Launcher.java:67)
BUILD SUCCESSFUL
Total time: 2 secondsso, code is not running......its dfinitely a classpath problem , because error message says "Could not find TestClient. Make sure you have it in your classpat".
TestClient is the name of main class file.
not sure whats wrong with this build.xml ? whats wrong in it ?
one thing , i guess, i did not mention "." , current directory in the build.xml ......is it because of that ?
i browsed apache manual......To Run a Java program.....first, they are making a JAR file ...and then they are executing the JAR.
i really, dont need the JAR file......i just want to run it.....thats enough.
somewhere, i have to do some modification in this buld.xml.......do you have any idea ?
thank you

TestClient folder has
1)src
2)classes
3)build.xml
i have posted the build.xml already.
now, src folder has TestClient.java
TestClient.java
==================
import org.apache.axis.client.Call;
import org.apache.axis.client.Service;
import javax.xml.namespace.QName;
public class TestClient {
   public static void main(String [] args) {
     try {
       String endpoint =
           "http://ws.apache.org:5049/axis/services/echo";
       Service service = new Service();
       Call     call    = (Call) service.createCall();
       call.setTargetEndpointAddress( new java.net.URL(endpoint) );
       call.setOperationName(new QName("http://soapinterop.org/","echoString"));
       String ret = (String) call.invoke( new Object[] { "Hello!" } );
       System.out.println("Sent 'Hello!', got '" + ret + "'");
     } catch (Exception e) {
       System.err.println(e.toString());
}and i did
ant runand i got those errors.
clearly, its not able to run it.
looked the manual....did not find anything special about java task....still not working.

Java static variables in Stored Java

I'm wondering if someone in Oracle could relate their thinking with regards to static variables in stored java and why were these implemented as they were. The aspect I'm referring to specifically is how these are basically working as PLSQL package variables, i.e. with state maintained for the life of the session.
Outside the database, in the "normal" Java world, statics will only live as long as the program is running. But in the Oracle DB world, the static continues to live as long as the session. With this in mind, doesn't this difference compromise the idea of just inserting working Java code into the Database? i.e. static variables now have to be initialized every time a method is called, and cannot be assumed to have default values. Does that not seem like a rather large departure from what a non-DB java programmer would be doing?
Thanks in advance for your thoughts on this.
Joe Tseng

It should generally be the case that all calls in a session see the same static variable values. Some actions will terminate the java session (and lose the static variable state) without ending the RDBMS session, such as calling System.exit from java, but normally this can't happen within a single RDBMS call. Perhaps if you give more details on how you are making the call from java to PLSQL one could say more. In particular, if the call happens to be via the JDBC thin driver then the session running in the JDBC connection will be distinct from the calling session.

Java Does Not Throw Exception When Writing To Read-Only Files

I have noticed that when I try to write to a read-only file in a window environment, Java does not throw an IOExcpetion, it just dosn't write to the file.
I am writing an FTP server and here is the code:
     public static long copyStream(InputStream in, OutputStream out)throws IOException
          IOException exception = null;
          long copied = 0;
          try
               byte buffer[] = new byte[1024];
               int read;
               while((read = in.read(buffer)) != -1)
                    out.write(buffer, 0, read);
                    copied += read;
          catch(IOException e)
               //ensures that the streams are closed.
               exception = e;
          try
               in.close();//ensures output stream gets closed, even if there is an
               //excption here.
          catch(IOException e){exception = e;}
          out.close();//try to close output.
          if(exception != null)
               //exception is not null, an exception has occured.
               //rethrow exception.
               throw exception;
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I have noticed that when I try to write to a read-only file in a window environment,
Java does not throw an IOExcpetion, it just dosn't write to the file.C:\source\java\Markov>attrib readonly.out
A R C:\source\java\Markov\readonly.out
�C:\source\java\Markov>java b
java.io.FileNotFoundException: readonly.out (Access is denied)
at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.<init>(Unknown Source)
at java.io.FileOutputStream.<init>(Unknown Source)
at b.main(b.java:5)
import java.io.*;
public class b {
    public static void main(String[] args) {
     try     {
          OutputStream os = new FileOutputStream ( "readonly.out");
     catch (Exception e) {
          e.printStackTrace();
}

Getting 'taglib directive for "f" does not exist or TLD is not found'

Hi,
I'm using Eclipse 3.4 and when I open my JSF page in Eclipse, I'm getting red "x"'s next to my JSF directives. For example,
<f:view>
has a red "x" along the left margin and when I roll over it, it gives me the error, 'taglib directive for "f" does not exist or TLD is not found.' This is odd because I have the appropriate directives, including
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %>
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Hi, I went to the link
http://java.sun.com/javaee/javaserverfaces/download.html
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JAVA Stack not starting up after System Copy

Hi,
We have done the system copy from Production to Sandbox and we are facing an issue with the JAVA Stack not starting up.
Following is the error in the SAPInst log file.
INFO
2014-09-07 18:06:48.86 [iaxxbfile.cpp:538]
CIaOsFile::chmod_impl(0755)
Authorizations set for /usr/sap/CS0/DVEBMGS00/data/icmandir/its/lsgui/images/list/symbols.
INFO
2014-09-07 18:06:50.494 [iaxxbfile.cpp:538]
CIaOsFile::chmod_impl(0755)
Authorizations set for /usr/sap/CS0/DVEBMGS00/data/icmandir/its/lsgui/js.
INFO
2014-09-07 18:06:50.819 [iaxxbfile.cpp:538]
CIaOsFile::chmod_impl(0755)
Authorizations set for /usr/sap/CS0/DVEBMGS00/data/icmandir/its/lsgui/js/texts.
ERROR
2014-09-07 18:06:55.22 [syxxcfsmgt.cpp:211]
CSyFileSystemMgtImpl::getNode(const CSyPath & path, CSyPath::NodeType nodeType) const
lib=syslib module=syslib
FSL-02015 Node /usr/sap/CS0/DVEBMGS00/data/stat46 does not exist.
INFO
2014-09-07 18:46:32.15 [iaxxbfile.cpp:538]
CIaOsFile::chmod_impl(0755)
Authorizations set for /usr/sap/CS0/DVEBMGS00/work/co.sapCS0_DVEBMGS00.
INFO
2014-09-07 18:46:35.895 [iaxxbfile.cpp:538]
CIaOsFile::chmod_impl(0755)
Authorizations set for /usr/sap/CS0/DVEBMGS00/work/dw.sapCS0_DVEBMGS00.
WARNING
2014-09-07 18:46:36.218
CJSlibModule::writeWarning_impl()
Broken link /usr/sap/CS0/DVEBMGS00/work/ig.sapCS0_DVEBMGS00 -> /usr/sap/CS0/DVEBMGS00/exe/igswd_mt detected.
Please guide.
Thanks,
CJ

For system of the J2EE stack did you use sapinst export and import ?
If the Java doesn't start then check the trace files (dev_server, std_server, bootstrap logs) present at /usr/sap/CS0/DVEBMGS00/work
Regards
RB

Do Static Classes exist?

Does Java allow the creation of static classes, and if so does that mean an instance of the class cannot be created? I know that a class can have static methods that only access static instance variables, but I don't know if that means that the class itself is static. I ask because I realized that you can't declare a static class like "public static class A {...}"

@OP. An inner class can be declared to be static,but
top level classes can't be static.
But that doesn't mean the static inner class
can't be instantiated (which seems to be what the OP
is thinking of).That was an answer to the topic - "Do static classes exist?", and the question does also say:
"Does Java allow the creation of static classes, and if so does that mean an instance of the class cannot be created?"
So I thought that the OP also wanted to know if static classes existed.
Kaj

How to add images into a java application (not applet)

Hello,
I am new in java programming. I would like to know how to add images into a java application (not an applet). If i could get an standard example about how to add a image to a java application, I would apreciated it. Any help will be greatly apreciated.
Thank you,
Oscar

Your' better off looking in the java 2d forum.
package images;
import java.awt.*;
import java.awt.image.*;
import java.io.FileInputStream;
import javax.imageio.ImageIO;
import javax.swing.*;
/** * LogoImage is a class that is used to load images into the program */
public class LogoImage extends JPanel {
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          super.paintComponent(g);
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          Graphics2D g2D = (Graphics2D) g;
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          LogoImage logoImage = new LogoImage();
          BufferedImage image;
          try {
               FileInputStream fileInput =
                    new FileInputStream("images/" + filename);
               image = ImageIO.read(fileInput);
               logoImage =
                    new LogoImage(
                         new Dimension(image.getWidth(), image.getHeight()));
               fileInput.close();
               logoImage.setImage(image);
          } catch (Exception e) {
               System.err.println(e);
          return logoImage;
     public static void main(String[] args) {
          JFrame jf = new JFrame("testImage");
          Container cp = jf.getContentPane();
          cp.add(LogoImage.createImage("logo.gif"), BorderLayout.CENTER);
          jf.setVisible(true);
          jf.pack();
}Now you can use this class anywhere in your pgram to add a JPanel

Invalid Class -Java Bean not available for import

hai friends,
i have declared the bean but unable to import into webdynpro application
i am geting the error invalid Class-java bean Not available for improt
i am try for this since more than 10 days , i get the same error
even i thought there may be issues with nwds , i have installed thrice.
there is application download from the sdn tu_bonus calculation it is working
plz help me neede very urgently

Hi,
Go thro' these solved threads dealing with similar type of problem,
Import JavaBean Error : Invalid Class
invalid class - ..as Model Class already exist
Hope it helps to fix the error !
Regards
Srinivasan T

PriorityQueue constructor in the java 5 api

Hi there.
I had a look at the following overloaded priorityqueue constructor in the Java 5 Api
as I am doing some practice and am playing around with them.
PriorityQueue(int initialCapacity, Comparator<? super E> comparator)I cant seem to find out what exactly the initialCapacity parameter does?
Any info appreciated.
Thanks & kind regards.

Did you read the [API docs|http://java.sun.com/javase/6/docs/api/java/util/PriorityQueue.html]?
A priority queue is unbounded, but has an internal capacity governing the size of an array used to store the elements on the queue. It is always at least as large as the queue size. As elements are added to a priority queue, its capacity grows automatically. The details of the growth policy are not specified.The initialCapacity would be the internal capacity the queue starts out with when constructed.

Is static constructors exist in java or not?

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