| Bug#365408: Millions of men use this |
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Index ‹ java-programmer
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- 2
- quartic polynomial solverHi,
I'm looking for a java method or Math lib which solves quartic
polynomial equations a4 x^4 + a3 x^3 + a2 x^2 + a1 x + a0 = 0.
My google results pointed to dead links. Any help appreciated.
Thanks,
Lothar Leidner
- 3
- SQL Server 2000 database connection problems: Can ANY one help?Environment: SQL Server 2000, Windows 2000, Eclipse, and Microsoft's SQL
Server 2000 driver for JDBC
Problem: Connection to any table in my SQL 2000 database hangs. If I stop
it, it produces the following exception:
com.sun.jdi.VMDisconnectedException: Got IOException from Virtual Machine
at
org.eclipse.jdi.internal.connect.PacketReceiveManager.getReply(PacketReceive
Manager.java(Compiled Code))
at
org.eclipse.jdi.internal.connect.PacketReceiveManager.getReply(PacketReceive
Manager.java:137)
at org.eclipse.jdi.internal.MirrorImpl.requestVM(MirrorImpl.java:168)
at org.eclipse.jdi.internal.MirrorImpl.requestVM(MirrorImpl.java:186)
at
org.eclipse.jdi.internal.ObjectReferenceImpl.invokeMethod(ObjectReferenceImp
l.java:350)
at
org.eclipse.jdt.internal.debug.core.model.JDIThread.invokeMethod(JDIThread.j
ava:647)
at
org.eclipse.jdt.internal.debug.core.model.JDIObjectValue.sendMessage(JDIObje
ctValue.java:67)
at
org.eclipse.jdt.internal.debug.eval.LocalEvaluationEngine.run(LocalEvaluatio
nEngine.java:231)
at
org.eclipse.jdt.internal.debug.core.model.JDIThread.runEvaluation(JDIThread.
java:562)
at
org.eclipse.jdt.internal.debug.eval.LocalEvaluationEngine.acceptClassFiles(L
ocalEvaluationEngine.java:218)
at
org.eclipse.jdt.internal.core.eval.RequestorWrapper.acceptClassFiles(Request
orWrapper.java:45)
at
org.eclipse.jdt.internal.eval.EvaluationContext.evaluate(EvaluationContext.j
ava:234)
at
org.eclipse.jdt.internal.eval.EvaluationContext.evaluate(EvaluationContext.j
ava:252)
at
org.eclipse.jdt.internal.core.eval.EvaluationContextWrapper.evaluateCodeSnip
pet(EvaluationContextWrapper.java:207)
at
org.eclipse.jdt.internal.debug.eval.LocalEvaluationEngine$1.run(LocalEvaluat
ionEngine.java:433)
at java.lang.Thread.run(Thread.java:498)
I have confirmed that server name is correct, and have pinged the port.
Looking at the following code snippet, what I am doing wrong?
Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
String url =
"jdbc:microsoft:sqlserver://niels-bngjqb9y1:1433;DatabaseName=Forester;";
Connection conn = null;
conn = DriverManager.getConnection(url,"sa","");
- 3
- jdbc on tomcatHi all,
I'm experiencing a unusual problem in
Apache Tomcat/4.1
sdk:1.4.1_03-b02
Linux 2.4.20-8 i386
I've got an application running on commons-DBCP
everything seems ok:
- libs in the commons/lib folder
- datasource in the context:
<Resource name="jdbc/devel4_minePooledDS" scope="Shareable"
type="javax.sql.DataSource"/>
<ResourceParams name="jdbc/devel4_minePooledDS">
<parameter>
<name>url</name>
<value>jdbc:oracle:thin:@10.10.45.4:1521:orlx</value>
</parameter>
<parameter>
<name>driverClassName</name>
<value>oracle.jdbc.driver.OracleDriver</value>
</parameter>
<parameter>
<name>factory</name>
<value>org.apache.commons.dbcp.BasicDataSourceFactory</value>
</parameter>
<parameter>
<name>maxIdle</name>
<value>30000</value>
</parameter>
<parameter>
<name>maxWait</name>
<value>500</value>
</parameter>
<parameter>
<name>maxActive</name>
<value>30</value>
</parameter>
<parameter>
<name>password</name>
<value>mine</value>
</parameter>
<parameter>
<name>username</name>
<value>mine</value>
</parameter>
</ResourceParams>
- enabled in web.xml:
<resource-ref>
<description>Resource for DB connections</description>
<res-ref-name>jdbc/devel4_minePooledDS</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
- used in this way:
InitialContext initCtx = new InitialContext();
DataSource ds =
(DataSource)initCtx.lookup("java:comp/env/jdbc/devel4_minePooledDS");
Connection conn = ds.getConnection();
- the application simply doesnt start with the following errors, not
so helpful, to be honest:
2004-05-04 09:46:06 StandardWrapperValve[action]: Allocate exception
for servlet action
javax.servlet.ServletException: Servlet.init() for servlet action
threw exception
at org.apache.catalina.core.StandardWrapper.loadServlet(Unknown
Source)
at org.apache.catalina.core.StandardWrapper.allocate(Unknown Source)
at org.apache.catalina.core.StandardWrapperValve.invoke(Unknown
Source)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(Unknown
Source)
at org.apache.catalina.core.StandardPipeline.invoke(Unknown Source)
at org.apache.catalina.core.ContainerBase.invoke(Unknown Source)
at org.apache.catalina.core.StandardContextValve.invoke(Unknown
Source)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(Unknown
Source)
at org.apache.catalina.core.StandardPipeline.invoke(Unknown Source)
at org.apache.catalina.core.ContainerBase.invoke(Unknown Source)
at org.apache.catalina.core.StandardContext.invoke(Unknown Source)
at org.apache.catalina.core.StandardHostValve.invoke(Unknown Source)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(Unknown
Source)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(Unknown
Source)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(Unknown
Source)
at org.apache.catalina.valves.ErrorReportValve.invoke(Unknown Source)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(Unknown
Source)
at org.apache.catalina.core.StandardPipeline.invoke(Unknown Source)
at org.apache.catalina.core.ContainerBase.invoke(Unknown Source)
at org.apache.catalina.core.StandardEngineValve.invoke(Unknown
Source)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(Unknown
Source)
at org.apache.catalina.core.StandardPipeline.invoke(Unknown Source)
at org.apache.catalina.core.ContainerBase.invoke(Unknown Source)
at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:594)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:392)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:565)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:619)
at java.lang.Thread.run(Thread.java:536)
----- Root Cause -----
java.lang.StackOverflowError
at gnu.xml.pipeline.ValidationConsumer$ChildrenRecognizer.acceptElement(ValidationConsumer.java:1795)
at gnu.xml.pipeline.ValidationConsumer$ChildrenRecognizer.acceptElement(ValidationConsumer.java:1795)
at gnu.xml.pipeline.ValidationConsumer$ChildrenRecognizer.acceptElement(ValidationConsumer.java:1795)
at gnu.xml.pipeline.ValidationConsumer$ChildrenRecognizer.acceptElement(ValidationConsumer.java:1795)
at gnu.xml.pipeline.ValidationConsumer$ChildrenRecognizer.acceptElement(ValidationConsumer.java:1795)
at gnu.xml.pipeline.ValidationConsumer$ChildrenRecognizer.acceptElement(ValidationConsumer.java:1795)
..
.
.
I didn't find anything similar
any helop will be appreciated
thanks in advance
jc
- 4
- Regular Expression to match the domain part of an email addressHi,
I'm trying to compile a regular expression that will match the domain
part of an email address. The email address has been split into 2
strings, the part before the @ sign and the part after the @ sign.
This regular expression is just working with the part after the @ sign.
The pattern that I have compiled appears to work for all combinations
except for something like:
a.com
b.com
However, the following do get matched:
a.co.uk
b.co.uk
I think the problem I have is because this combination is only a single
character long. The regular expression is truly horrendous, but I'm now
stuck with the way it has been done and need to figure out how to
modify it to accept the combination of "a.com" as a domain part of an
email address.
Can anyone tell me what's causing this problem from the expression
below?
Pattern.compile("^([\\*\\w]([\\*\\w\\-]{0,61}[\\*\\w])?\\.)*[\\*\\w]([\\*\\w\\-]{0,61}[\\*\\w])\\.[\\*\\w]([\\*\\w\\-]{0,61}[\\*\\w])?$");
Many thanks,
Emma
- 6
- 6
- Problem With Eclipse IDE and perforce plugin.Hi I am running Eclipse SDK Version: 3.1.0 Build id: I20050627-1435
It has perforce plugin P4WSAD Client API Team provider core and
Provider UI all version 2005.2.3573
Each time I compile the project I got follows exception. I does not
prevent from working successfully but kind annoing.
Error 2006-10-19 10:46:56.703 Problems occurred when invoking code from
plug-in: "org.eclipse.core.resources".
java.lang.NullPointerException
at
com.perforce.team.ui.actions.TeamAction.getShell(TeamAction.java:154)
at
com.perforce.team.ui.actions.AddEditDeleteAction.doAddEditDelete(AddEditDeleteAction.java:70)
at
com.perforce.team.ui.PerforceMarkerManager.resourceChanged(PerforceMarkerManager.java:111)
at
org.eclipse.core.internal.events.NotificationManager$2.run(NotificationManager.java:276)
at
org.eclipse.core.internal.runtime.InternalPlatform.run(InternalPlatform.java:1044)
at org.eclipse.core.runtime.Platform.run(Platform.java:783)
at
org.eclipse.core.internal.events.NotificationManager.notify(NotificationManager.java:270)
at
org.eclipse.core.internal.events.NotificationManager.broadcastChanges(NotificationManager.java:144)
at
org.eclipse.core.internal.resources.Workspace.broadcastBuildEvent(Workspace.java:185)
at
org.eclipse.core.internal.events.AutoBuildJob.doBuild(AutoBuildJob.java:140)
at
org.eclipse.core.internal.events.AutoBuildJob.run(AutoBuildJob.java:200)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:76)
Thank u Vlad.
- 6
- Specify security access in JNLPIs it possible to specify what access the web start application needs to
run?
Using the JNLP code
<security>
<all-permissions/>
</security>
All access can be gained, but I would like to restrict it to contacting
certain servers and clipbaord access. More like 'java.awt.AWTPermission
"accessClipboard"'. Is it possible to use this policy code in the JNLP file?
G
- 6
- What is meant by 'canonical representation'Hi,
I was reading the sun java api 1.4.2 and found the following for
String.intern().
public String intern()
Returns a canonical representation for the string object.
What is a canonical representation? Any example?
//Mikael
- 12
- Register Now - BOF 36 JBoss SEAM and JavaServerFacesHello world,
This is a quick reminder that the BOF 36 is still on track as
scheduled for the 16th of April. If you are in or around London area
and think you would like to attend but missed the initial
announcement, well here's the link again
ttp://www.jroller.com/javawug/entry/javawug_bof_36_jboss_seam.
Secondly, I would also like to formally announce that there is a Code
Camp holding on the 19th of April at the same venue. More about the
Code Camp later.
Please note that these are TOTALLY FREE events organised by the London
based JavaWUG. So, just put your name down and come along.
http://www.jroller.com/javawug/entry/javawug_bof_36_jboss_seam#register
If you have any queries or need something clarified, please leave a
comment on this page.
Evans Anyokwu
http://www.javawug.org
- 13
- Trying to store fixed dates in calendar....hi,
sorry to bother you with a question somebody should have already ask,
but i was unable to find it in groups.google.com.. so ;)=
well, my problem is that i'm trying to store dates values in Calendar
(more exactly GregorianCalendar) class instances.
BUT... the stored dates keep on running upon the system date :
ie : i store 2h 34m 5s 324ms
4s later, when i print the date, it will give me something like
2h 34m 9s 450ms
it is very bothering for me...
how can i make Calendar class to store "fixed" dates... ?
or which class should i use to store "fixed" dates ?
Thanx for your help.
Pierre-Yves
- 13
- ORBSocketFactory in JDK15I've created an ORBSocketFactory for use in JDK14. I now need to create one
for JDK15. It seems that the interface has substantially changed and that
it no longer provides the IOR, which I need access to to decide what kind of
socket to create.
The JDK14 classes had extensive javadocs. The JDK15 classes have zippo.
Can someone provide some useful tips on porting?
Regards,
Alan
- 14
- applet doesn't find jars !!Greetings, I'm trying to create graphics with jfree in an applet
here are the facts :
<HTML>
<HEAD>
<TITLE>Hello to Everyone!</TITLE>
</HEAD>
<BODY>
<APPLET codebase="http://localhost/applets/classes"
CODE="AppletBarChartDemo.class"
WIDTH="400"
HEIGHT="325"
archive="jfreechart-0.9.18.jar, jcommon-0.9.3.jar, log4j-1.2.8.jar>
<PARAM name="sourcexml" value="donnees.xml" >
</APPLET>
</BODY>
</HTML>
My console says :
java.io.IOException: Server returned HTTP response code: 400 for URL:
http://localhost/applets/classes/log4j-1.2.8.jar>
java.lang.NoClassDefFoundError: org/apache/log4j/Logger
java.lang.NoClassDefFoundError at
org.jfree.chart.ChartFactory.createBarChart(ChartFactory.java:386)
java.lang.NoClassDefFoundError at
org.jfree.chart.ChartFactory.createBarChart(ChartFactory.java:386)
but my webserver (IIS on w2K) structure is thus :
root/applets/classes/
in it, I got the class files and the afore mentioned jars
And of course, I can run it under eclipse as an applet !!!
Browsers tested are IE6 and Firefox..
any tips ?
- 14
- Adding Fractions ProblemI can use the code below to add fractions together through adding instances
of the class Rational together, but my code to reduce the result to its
lowest terms has no effect. Why is this?
public class Rational
{
// instance variables - replace the example below with your own
private int numerator;
private int denominator;
public Rational()
{
}
public Rational(int num, int denom)
{
numerator = num;
denominator = denom;
}
public int getNumerator()
{
return numerator;
}
public int getDenominator()
{
return denominator;
}
public Rational add(Rational rhs)
{
int numerator1 = (rhs.getDenominator() * numerator);
int newDenom = (rhs.getDenominator() * denominator);
int numerator2 = (denominator * rhs.getNumerator());
int newNum = (numerator1 + numerator2);
if((newDenom % newNum) == 0)
{
// This code is supposed to reduce the result to its lowest
terms
int commonFactor = (newDenom / newNum);
newDenom /= commonFactor;
newNum /= commonFactor;
}
return new Rational(newNum, newDenom);
}
}
- 14
- Question: Gui Looks DifferentI am a fairly new java developer, so the answer to my question may be
obvious to the veterans, but it is not obvious to me, so here goes. I
have an application that has several progress bars and other guid
widgets in it. On the system (a desktop with CRT) where the code was
developed the GUI looks normal. If I run the same code on my laptop,
the app still runs but the GUI is not drawn correctly. Is there a fix
(easy or otherwise) for this? Many thanks in advance,
Ken Browning
- 14
- Response Control ProblemI am trying to connect to IBM Directory server using Sun JNDI
implementation. The scenario: Connecting to the directory using an
expired password. When I do this I expect to get a Password Expiration
response control that indicates that the password has been expired.
However when i execute the code I get no response control. The context
returned is null. Snippet of my code is shown below:
Hashtable env = new Hashtable(11);
env.put( Context.INITIAL_CONTEXT_FACTORY,
"com.sun.jndi.ldap.LdapCtxFactory");
env.put(Context.PROVIDER_URL, "ldap://.../");
env.put(Context.SECURITY_AUTHENTICATION, "simple");
env.put(Context.SECURITY_PRINCIPAL, "dn...");
env.put(Context.SECURITY_CREDENTIALS, "...");
Control[] ctls = new Control[] {new PasswordPolicyRequestControl()};
ldapctx = new InitialLdapContext(env,ctls);
It throws AuthenticationException where I try to get the response
control but it returns null.
Thanks.
Ashish
|
| Author |
Message |
marke kawaguchi
|
 Posted: 2008-3-25 18:01:00 |
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Index ‹ java-programmer |
- Next
- 1
- [ANNOUNCEMENT]:VTD-XML released under GPL I am pleased to announce that version 0.5 of VTD-XML -- a new,
non-extractive, Java-base XML processing API licensed under GPL
-- is now freely available on sourceforge.net. For source code,
documentation, detailed description of API and code examples,
please visit
http://vtd-xml.sf.net
Capable of random-access, VTD-XML attempts to be both memory
efficient and high performance. The starting point of this project is
the observation that, for XML documents that don't declare entities
in DTD, tokenization can indeed be done by only recording the starting
offset and length of a token. A discussion on this subject appeared
in a recently article on xml.com
(http://www.xml.com/pub/a/2004/05/19/parsing.html).
The core technology of VTD-XML is a binary format specification
called Virtual Token Descriptor (VTD). A VTD record is a 64-bit integer
that encodes the starting offset, length, type and nesting depth of a
token in an XML document. Because VTD records don't contain actually
token content, they work alongside of the original XML document, which
is maintained intact in memory by the processing model.
VTD's memory-conserving features can be summarized as follows:
* Avoid Per-object overhead -- In many VM-based object-oriented
programming languages, per-object allocation incurs a small amount
of memory overhead. A VTD record is immune to the overhead because
it is not an object.
* Bulk-allocation of storage -- Fixed in length, VTD records can be
stored in large memory blocks, which are more efficient to allocate
and GC. By allocating a large array for 4096 VTD records, one incurs
the per-array overhead (16 bytes in JDK 1.4) only once across 4096
records, thus reducing per-record overhead to very little.
Our benchmark indicates that VTD-XML processes XML at the performance
level similar to (and often better than) SAX with NULL content handler.
The memory usage is typically between 1.3x ~ 1.6x of the size of the
document, with "1" being the document itself.
Other features included in this release are:
* Incremental update -- VTD-XML allows one to modify content of XML
without touching irrelevant parts of the document.
* Content extraction -- VTD-XML also allows one to pull an element
out of XML in its serialized format. This can be an important
feature for partial signing/encryption of SOAP payload for
WS-security.
In the upcoming releases, we plan to add the persistence support so
that one can save/load VTD to/from the disk along with the XML documents
to avoid repetitive parsing in read-only situations. XPATH support is
also on the development roadmap. However, we would like to collect as
many suggestions and bug reports before taking the next step.
Your input and suggestions are very important to make VTD-XML a truly
useful XML processor.
Thanks,
Jimmy Zhang
- 2
- Sun J2SE 1.4.2 max heap sizeHi there !
Can anyone confirm what is the max heap size for the VM in Sun's J2SE
1.4.2 SDK (for windows 64b Itanium 2) ?
In the documentation it is mentioned that for Solaris we have a 64b
address space but I couldn't find anything regarding wintel 64b and I
would like to confirm.
Thanks/Brgds
Joao
- 3
- Clob trim leaves open cursorsHi,
I have a program which inserts/updates hundreds of clob values in an
Oracle database table. I'm getting a "maximum open cursors" error
when I run this program:
ORA-01000: maximum open cursors exceeded
ORA-06512: at "SYS.DBMS_LOB", line 527
To troubleshoot, I tried checking the v$open_cursor table periodically
during the program run by running this SQL query:
select user_name, sql_text from v$open_cursor
The vast majority of the open cursors had the following sql_text
value:
begin dbms_lob.trim (:1, :2); end;
I ran this program before without problems; the only major thing that
I've changed is to add a clob.trim() call, which I realized was
necessary in case the new clob value was longer than the old clob
value.
Below is the method that's being called repeatedly, where
"retrieveClobQuery" is an SQL query to select the clob value, and
"clobData" is the new clob value to be inserted. The same Connection
(conn) is used throughout. A new Statement is created and closed each
time. (I tried rewriting the code to use the same Statement
throughout, but it didn't seem to make a difference.)
public void singleClobUpdate(String retrieveClobQuery, String
clobData) {
Statement stmt = null;
try {
conn.setAutoCommit(false);
stmt = conn.createStatement();
// Use "for update" parameter to lock the row
ResultSet rs = stmt.executeQuery(retrieveClobQuery + " for
update");
if (rs.next()) {
// Get clob value and cast to oracle.sql.CLOB
CLOB clob = (CLOB)rs.getObject(1);
// Write the data to the clob object
Writer writer = clob.getCharacterOutputStream();
writer.write(clobData);
writer.flush();
writer.close();
// trim clob in case new clob contains less data than
previous one
clob.trim(clobData.length());
}
// Commit changes to release the lock
conn.commit();
conn.setAutoCommit(true);
stmt.close();
}
catch (Exception e) {
e.printStackTrace();
if (stmt != null) {
try {
stmt.close();
}
catch (SQLException e) {}
}
}
}
Any help would be greatly appreciated.
Thanks!
- 4
- grid of JLabelsI want to make a grid of JLabels. I want to have 4 rows and 4
columns.Any ideas?
thanks in advance
- 5
- Spring/Tomcat/Ant/Java developmentHi there,
I am trying to build my first application with the Spring framework,
Apache Tomcat and Ant. I am having trouble accessing the application.
When I try to build it with Ant I get this error:
/home/workspace/springapp/build.xml:78: taskdef class
org.apache.catalina.ant.InstallTask cannot be found
Here is my build.properties file:
appserver.home=home/apache-tomcat-5.5.20
appserver.name=tomcat
deploy.path=${appserver.home}/webapps
tomcat.manager.url=http://localhost:8080/manager
tomcat.manager.username=<username>
tomcat.manager.password=<password>
And build.xml (just where the problem is occuring, since the whole file
is rather lengthy):
<taskdef name="install"
classname="org.apache.catalina.ant.InstallTask">
<classpath>
<path
location="${appserver.home}/server/lib/catalina-ant.jar"/>
</classpath>
</taskdef>
<taskdef name="reload"
classname="org.apache.catalina.ant.ReloadTask">
<classpath>
<path
location="${appserver.home}/server/lib/catalina-ant.jar"/>
</classpath>
</taskdef>
<taskdef name="list" classname="org.apache.catalina.ant.ListTask">
<classpath>
<path
location="${appserver.home}/server/lib/catalina-ant.jar"/>
</classpath>
</taskdef>
<taskdef name="start"
classname="org.apache.catalina.ant.StartTask">
<classpath>
<path
location="${appserver.home}/server/lib/catalina-ant.jar"/>
</classpath>
</taskdef>
<taskdef name="stop" classname="org.apache.catalina.ant.StopTask">
<classpath>
<path
location="${appserver.home}/server/lib/catalina-ant.jar"/>
</classpath>
</taskdef>
Does anyone have a clue as to what I'm doing wrong??
Many thanks,
Courtney
- 6
- Multiple Inheritance In Javahi everyone
this is my first post since i joined the group a week ago.
I m working with java for a year now since i come from a C++
background i can't help comparing the two languages.
While studying for java i found many books stating that java does not
support multiple inheritance i don't fully agree with this notion
(please don't hate me for that).
Though it is true that one cannot extend more than one class at a time
which makes perfect sense
since all the classes in java are derived from Object class and
multiple extensions would
cause multiple objects of Object to exist in the code which could be
undesirable.However java could
have provided a concept similar to virtual base classes in C++ but it
would have to be implicit like the extension to
the Object class and moreover multiple calls to the virtual base
class's(Object) constructor would have to be avoided.
(in C++ the compiler donot call the constructor of a virtual base class
from immediate derivations
rather it allows the class which is extending multiple derivations of
the virtual base class to call its
constructor directly, something which is not legal for ordinary base
classes) .Java could not provide a solution like this
since the only way to call the superclass constructor is by keyword
super which can call the constructor of
the immediate superclass only.So it is true that allowing multiple
extensions would have caused more problems
than it could solve.Still while creating patterns multiple inheritance
is sometimes inevitable.The solution to this
problem is interface.An interface in java is used to create a model of
a class,it just declare the behaviour(methods) that
a class must implement.It is worth noting that code reusabilty ,a
criteria generally used to define inheritance,while implementing an
interface is nil.That is why implementing an interface is not qualified
as inheritance.However if you have ever indulged yourself in creating
design patterns you would know that inheritance is more than just code
reusability rather in my opinion code reusability is just a consequence
of implementing inheritance in programming languages. Java allows a
class to implement more than one interface in this way a class can
implement 'behaviours' of multiple classes and thus to an extent
solving the multiple inheritance problem(without providing code
reusability).
So the question is that is it alright to say that java does not
support multiple inheritance?
nirmal.
- 7
- Creating Forms in JSPHi ,
I want to create a sample aplication in JSP , which consits of
a basic form , and when the user gives in data in the form , the data
should be stored in the database, and then should be retrived back
when required. Can any one please help out in this as im a total
fresher in JSP .
Please help me out in this..
Thanks in ADVANCE
Sagar meesala
- 8
- destructor neededI have objects that are added as listeners
to various system events (such as change of
language or units etc.).
To subscribe to such events I typically call
someManager.addListener(this); and the "this"
object will be added in a subscription list
of someManager.
My problem is when these objects are no longer
needed. Normally they would be GC'd, but because
of the subscription references they are not,
and the memory is in effect lost.
My current approach is to have a destroy()
method on these objects where I unsubscribe
to system events (removeListener). I am then
forced to think C++ and figure out when the
object actually dies and call the destroy()
method there, which is a pain as it may
include calling destroy() of children objects
etc. and in general it will be very hard to
get rid of them all.
As I assume my architechture is commonplace,
some of you might have a brigther solution
to the problem?
Thanks!
- 9
- Why does JMenuItem react to right button?In all the applications that I know, menu items react only to mouse
left-click. Swing JMenuItem, however, reacts to any mouse button click.
Swing JButton (which also extends AbstractButton) behaves as expected.
Does anybody know why? Is there any way to change this behavior?
Thanks in advance,
Diego
- 10
- 11
- [OT] Re: Yet Another Web Application Mess...Hi,
Roedy Green wrote:
>... in the early 80...
> It will be that class's concern alone that
> Germans have a two part zip code.
Note that this was true in the early 80es but is no longer true since...
ah... the late 80es.
SCNR,
Ingo,
33615 Bielefeld
- 12
- Starting the RMI Serverhi,
I have a class which tests to see if an rmi server is bound to the rmi
registry, if not it binds it and if the registry is not running it starts
one with
Process child = Runtime.getRuntime().exec("batch file").
then binds the server to the newly running registry
It does this in a while(true) with a break; when the server is bound to the
registry.
This class does what I want. I have now tried to convert this into a bean,
and have all of the variables and the get/set methods to access them via the
ide propery sheet. However, when I drop this onto a project the code runs
(straightaway in the ide forte & beanbox, without me compiling and running
the project I have dropped it into) - ie the while loop runs immediatly and
does not break; - it goes crazy and starts opening windows. What have I
done wrong - I don't think I have changed the code much since the standalone
calss (apart from the get/set methods, replacing strings with String vars) ?
The code which does all the work is in the default constructor (moved from
main in the original class). Does the ide instantiate the bean when dropped
from the palette onto a project? If so, how can I resolve the issue, if not
then why is the code running without me compiling/running the project?
I have also had trouble with the setSecurityManager(new
RMISecurityManager()) and have been tinkering with the polcy files to see if
that is fixable.
thanks
Mike
- 13
- FTPClient and CopyStreamAdapter stop sometimesI have an applet which Downloads some files from an FTP(S) Server.
Mostly everything works fine, but sometimes the application "stops"
for a long time (several minutes) after the "RETR filename" command.
PErhaps someone knows this problem or has an idea.
Thank you in advance for any hint,
Susanne
Here is some of my code:
try {
InputStream stO =
new BufferedInputStream(
ftps.retrieveFileStream(fileName),
ftps.getBufferSize());
org.apache.commons.net.io.Util.copyStream(
stO,
fout,
ftps.getBufferSize(),
//
org.apache.commons.net.io.CopyStreamEvent.UNKNOWN_STREAM_SIZE,
length,
new org.apache.commons.net.io.CopyStreamAdapter() {
public void bytesTransferred(long
totalBytesTransferred,
int bytesTransferred,
long streamSize) {
changeSupport.firePropertyChange(FTPPERCENT, null,
totalBytesTransferred*100/length);
}
});
} catch (Exception e) {
e.printStackTrace();
}
- 14
- newbie: "reference to object is ambiguous" errorHi!
I have this error compilling my application that I have created with
netbeans:
JFrameSample.java:164: reference to Object is ambiguous, both class
org.omg.CORBA.Object in org.omg.CORBA and class java.lang.Object
in java.lang match
new Object [][] {
^
1 error
How can I fix it? I need both: org.omg.CORBA and java.lang.*
any ideas?
Thanks!
LaCo
- 15
- Comparing two long numbersJohn B. Matthews <email***@***.com> wrote:
>> I meant (Math.sqrt(5.)-1)/2, which is theoretically the same, but
>> numerically more stable, since the divisor is simpler.
>> But then it would be Math.PHI, and at least as exact as each of the
>> formulae, if not better than both. :-)
> You're right: I inverted but didn't simplify! But isn't
> (Math.sqrt(5.)-1)/2 equal to 1 / phi?
IIRC, PHI is the one with a "1" before the decimal point, so, yes,
your aspect ration was near 1/PHI actually. The other solution
of "x = 1/x + 1" is -1/PHI (-0.618...)
Just hold the height fixed, and make the width of your component
<wish>Math.PHI</wish> times longer. Or if really the width is
given, then make the height a PHI'th.
PS: I think we should think about ending this subthread, shouldn't we?
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