How to avoid multiple instances of a class
I new a class
var myCourse=new course();
myCourse.newCourse(value);
add myCourse;
Now ,I want call function newCourse many times and don`t new class again
how to do ...?
As long as you do not use "var myCourse=new course();" again you can use "myCourse.newCourse(value);" as often as you like without creating a new instance.
Similar Messages
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Creating multiple instances of a class in LabVIEW object-oriented programming
How do you create multiple instances of a class in a loop? Or am I thinking about this all wrong?
For instance, I read in a file containing this information:
Person Name #1
Person Age #1
Hobby #1
Hobby #2
Hobby #3
Person Name #2
Person Age #2
Hobby #1
Hobby #2
Hobby #3
Person Name #3
Person Age #3
Hobby #1
Hobby #2
Hobby #3
If I define a Person class with name, age, and an array of strings (for the hobbies), how can I create several new Person instances in a loop while reading through the text file?
FYI, new to LabVIEW OOP but familiar with Java OOP. Thank you!First of all, let's get your terminology correct. You are not creating multiple instances of a class. You are creating Objects of the class.
Use autoindexing to create an array of your class type.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines -
I have written a class, called Board. In my program, I need to create multiple instances of this class. e.g. Board1, Board2, Board3 etc.
Board Board2 = new Board();
Board2 = Board1;
However, when I change some parameters in Board1, the parameters in Board2 also get changed. Is there a way to prevent this?
I tried using the Object.clone() method, but I can't seem to invoke it due to its protected nature. If this is indeed the solution, does anybody know how to invoke it? Thanks!
PerdI am interested in your alternative solution of
implementing clone() as a public method. However, I
don't really understand what do you mean by that.
I tried something like this:
class Board extends Cloneable
but it still doesn't work.
Can you please explain in greater detail what do you
mean? thanks!Read this: http://java.sun.com/docs/books/tutorial/java/javaOO/objectclass.html -
How to avoid multiple listing for same artist?
How to avoid multiple listing for same artist?
Sounds like there might be blanks in the artist name.
For instance "Lou Reed" and "Lou Reed_" will not match.
(Pretend the underscore _ is a blank).
Select all the Lou Reed songs, Get Info, and type "Lou Reed" in the artist field. That should fix it. -
How to create multiple instance on same database
Hi ,
I would like to know how to create multiple instance on same database . I know that some people use database configuration assistant to do this but i could not figure out how they did it.
Any how if some one can help me with this and can give me links of this it would be great help for me.
Thank you for reading my problem and helping me !
Amil
please if possible mail me on [email protected]How to create multiple instance?????Do you mean multiple instances on the same database, or multiple databases on the same machine ?
I m new to this field....
Willin to learn a lot about oracle....Then it wouldn't be bad reading a bit of Database Concepts -
In a SQL query whihc has join, How to reduce Multiple instance of a table
in a SQL query which has join, How to reduce Multiple instance of a table
Here is an example: I am using Oracle 9i
is there a way to reduce no.of Person instances from the following query? or can I optimize this query further?
TABLES:
mail_table
mail_id, from_person_id, to_person_id, cc_person_id, subject, body
person_table
person_id, name, email
QUERY:
SELECT p_from.name from, p_to.name to, p_cc.name cc, subject
FROM mail, person p_from, person p_to, person p_cc
WHERE from_person_id = p_from.person_id
AND to_person_id = p_to.person_id
AND cc_person_id = p_cc.person_id
Thnanks in advance,
Babu.SQL> select * from mail;
ID F T CC
1 1 2 3
SQL> select * from person;
PID NAME
1 a
2 b
3 c
--Query with only ne Instance of PERSON Table
SQL> select m.id,max(decode(m.f,p.pid,p.name)) frm_name,
2 max(decode(m.t,p.pid,p.name)) to_name,
3 max(decode(m.cc,p.pid,p.name)) cc_name
4 from mail m,person p
5 where m.f = p.pid
6 or m.t = p.pid
7 or m.cc = p.pid
8 group by m.id;
ID FRM_NAME TO_NAME CC_NAME
1 a b c
--Expalin plan for "One instance" Query
SQL> explain plan for
2 select m.id,max(decode(m.f,p.pid,p.name)) frm_name,
3 max(decode(m.t,p.pid,p.name)) to_name,
4 max(decode(m.cc,p.pid,p.name)) cc_name
5 from mail m,person p
6 where m.f = p.pid
7 or m.t = p.pid
8 or m.cc = p.pid
9 group by m.id;
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 902563036
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 3 | 216 | 7 (15)| 00:00:01 |
| 1 | HASH GROUP BY | | 3 | 216 | 7 (15)| 00:00:01 |
| 2 | NESTED LOOPS | | 3 | 216 | 6 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL| MAIL | 1 | 52 | 3 (0)| 00:00:01 |
|* 4 | TABLE ACCESS FULL| PERSON | 3 | 60 | 3 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
Predicate Information (identified by operation id):
4 - filter("M"."F"="P"."PID" OR "M"."T"="P"."PID" OR
"M"."CC"="P"."PID")
Note
- dynamic sampling used for this statement
--Explain plan for "Normal" query
SQL> explain plan for
2 select m.id,pf.name fname,pt.name tname,pcc.name ccname
3 from mail m,person pf,person pt,person pcc
4 where m.f = pf.pid
5 and m.t = pt.pid
6 and m.cc = pcc.pid;
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 4145845855
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 1 | 112 | 14 (15)| 00:00:01 |
|* 1 | HASH JOIN | | 1 | 112 | 14 (15)| 00:00:01 |
|* 2 | HASH JOIN | | 1 | 92 | 10 (10)| 00:00:01 |
|* 3 | HASH JOIN | | 1 | 72 | 7 (15)| 00:00:01 |
| 4 | TABLE ACCESS FULL| MAIL | 1 | 52 | 3 (0)| 00:00:01 |
| 5 | TABLE ACCESS FULL| PERSON | 3 | 60 | 3 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
| 6 | TABLE ACCESS FULL | PERSON | 3 | 60 | 3 (0)| 00:00:01 |
| 7 | TABLE ACCESS FULL | PERSON | 3 | 60 | 3 (0)| 00:00:01 |
Predicate Information (identified by operation id):
1 - access("M"."CC"="PCC"."PID")
2 - access("M"."T"="PT"."PID")
3 - access("M"."F"="PF"."PID")
PLAN_TABLE_OUTPUT
Note
- dynamic sampling used for this statement
25 rows selected.
Message was edited by:
jeneesh
No indexes created... -
How to avoide multiple duplicate entries in adress book?
How to avoide multiple duplicate entries in adress book? I can add the same contact name and number more than twice and the phone isn't warning me at all!!! I's quite a heck for me.
not possible from inside AB AFAIK. but you can do the following. in finder open the folder /users/username/library/application support/address book/metdata. switch to the list mode and sort by date modified. quicklook the vcards at the top to see which ones they are.
-
How to avoid multiple copies of data in page refresh
How to avoid multiple copies of data in page refresh
If you are talking about a page with an insert query, ignore the fact that it's a page refresh. It's just another way that someone can insert duplicate records. I like to handle this in my insert query.
insert into thetable
(f1, f2, etc)
select distinct
value1, value2, etc
from some_small_table
where you don't already have that record -
How to allow multiple instances of air desktop application
hi all
Adobe air desktop application only allow single instance of
application. How to allow multiple instances like in other desktop
applications?.
thanksThanks a lot morgair, i will check with exe4j tool.
Actually the problem is, thread is not waiting for second request.
thatswhat i thought it may because of thread.
Thanks & Regards
Sudha -
How to create Multiple instances of This SingleTon class
import java.io.*;
import java.util.Properties;
import java.net.URLEncoder;
public class ddd
// declaring variables
static private ddd _instance;
String connectIP;
int connectPort;
String systemID;
String password;
String systemType;
// Constructor with arguments
private ddd()
globalInit();
// method returning the ddd instance.
public static synchronized ddd getInstance()
if (_instance == null)
_instance = new ddd();
return _instance;
// Global initialisations
public void globalInit()
systemID ="XXXXX" ;
password ="XXXXX";
systemType ="Null";
public static void main(String[] args)
ddd sb;
sb = ddd.getInstance();
System.out.println(ddd.getInstance());Don't cross-post:
http://forum.java.sun.com/thread.jsp?thread=547911&forum=54&message=2669925
http://forum.java.sun.com/thread.jsp?thread=547912&forum=31&message=2669928
Sorry, I can't help but think that this is one of the more foolish questions I've read in a while.
The pattern Singleton means "I only want one of these in a single JVM". If you want multiple instances, or even a restricted number of instances, then rewrite the class (something like this):
public class LimitedEdition
public static final int MAX_EDITIONS = 3;
private static int numEditions;
public static void main(String [] args)
try
if (args.length > 0)
int numEditions = Integer.valueOf(args[0]).intValue();
for (int j = 0; j < numEditions; ++j)
LimitedEdition limited = new LimitedEdition();
System.out.println(limited);
catch (Exception e)
e.printStackTrace();
public LimitedEdition() throws InstantiationException
if (numEditions < MAX_EDITIONS)
++numEditions;
else
throw new InstantiationException("Only " + MAX_EDITIONS + " instances allowed");
public String toString()
return "[ instance # " + numEditions + "]"; -
How to reference multiple instances of the same Java object from PL/SQL?
Dear all,
I'm experimenting with calling Java from PL/SQL.
My simple attempts work, which is calling public static [java] methods through PL/SQL wrappers from SQL (and PL/SQL). (See my example code below).
However it is the limitation of the public static methods that puzzels me.
I would like to do the following:
- from PL/SQL (in essence it needs to become a forms app) create one or more objects in the java realm
- from PL/SQL alter properties of a java object
- from PL/SQL call methods on a java object
However I fail to see how I can create multiple instances of an object and reference one particular object in the java realm through public static methods.
My current solution is the singleton pattern: of said java object I have only 1 copy, so I do not need to know a reference to it.
I can just assume that there will only ever be 1 of said object.
But I should be able to make more then 1 instance of an object.
To make it more specific:
- suppose I have the object car in the java realm
- from PL/SQL I want to create a car in the java realm
- from PL/SQL I need to give it license plates
- I need to start the engine of a scpecific car
However if I want more then 1 car then I need to be able to refrence them. How is this done?
Somehow I need to be able to execute the following in PL/SQL:
DECLARE
vMyCar_Porsche CAR;
vMyCar_Fiat CAR;
BEGIN
vMyCar_Porsche = new CAR();
vMyCar_Fiat = new CAR();
vMyCar_Porsche.setLicensePlates('FAST');
vMyCar_Porsche.startEngine();
vMyCar_Fiat.killEngine();
END;
Thanks in advance.
Best Regards,
Ruben
My current example code is the following:
JAVA:
===
CREATE OR REPLACE AND RESOLVE JAVA SOURCE NAMED CODAROUL."RMG/BO/RMG_OBJECT" as package RMG.BO;
public class RMG_OBJECT {
private static RMG_OBJECT instance = new RMGOBJECT();
private String rmgObjectNaam;
private RMG_OBJECT(){
this.rmgObjectNaam = "NonDetermined";
public static String GET_RMGOBJECT_NAAM () {
String toestand = null;
if (_instance == null) {toestand = "DOES NOT EXIST";} else { toestand = "EXISTS";};
System.out.println("instance : " + toestand);
System.out.println("object name is : " + _instance.rmgObjectNaam);
return _instance.rmgObjectNaam;
public static Integer SET_RMGOBJECT_NAAM (String IN)
try
_instance.rmgObjectNaam = IN;
return 1;
catch (Exception e)//catch
System.out.println("Other Exception: " + e.toString());
e.printStackTrace();
return 5;
} //catch
PL/SQL Wrapper:
==========
CREATE OR REPLACE FUNCTION CODAROUL.SET_RMGOBJECT_NAAM(NAAM IN VARCHAR2) return NUMBER AS
LANGUAGE JAVA NAME 'RMG.BO.RMG_OBJECT.SET_RMGOBJECT_NAAM (java.lang.String) return java.lang.Integer';
Calling from SQL:
==========
CALL dbms_java.set_output(2000);
select CODAROUL.GET_RMGOBJECT_NAAM() from dual;
Edited by: RubenS_BE on Apr 6, 2012 5:35 AM
Edited by: 925945 on Apr 6, 2012 5:41 AMYou can do this by manually creating a new iterator binding in your binding tab.
So instead of dragging the VO directly to the page, go to the binding tab, add a new executable iterator binding, and point to that one from your ELs in the page itself. -
How to avoid multiple if else using design patterns.
Hi,
Which design patterns is used to avoid lot of if else in our code . Say for example if the user press 1 the out put should be one, if he press 2 it should be two like this upto 10. So we need to include lot of if-else part. How to avoid the multiple if else using design patter for this scenario. I can't find the solution for this problem can you guys help me?.I'm too lazy to read a whole text book, but the first google link provides a code sample which made me laugh.
http://www.refactoring.com/catalog/replaceConditionalWithPolymorphism.html
double getSpeed() {
switch (_type) {
case EUROPEAN:
return getBaseSpeed();
case AFRICAN:
return getBaseSpeed() - getLoadFactor() * _numberOfCoconuts;
case NORWEGIAN_BLUE:
return (_isNailed) ? 0 : getBaseSpeed(_voltage);
throw new RuntimeException ("Should be unreachable");
}My implementation of The Bridge Over The Parrot Shop
package forums;
import java.util.Random;
abstract class Bird {
private static final Random random = new Random();
abstract double getAirSpeed();
public double getBaseSpeed() {
return randomDouble(18.96);
protected static double randomDouble(double max) {
return random.nextDouble() * max;
protected static int randomInt(int max) {
return random.nextInt(max);
class EuropeanSwallow extends Bird {
double getAirSpeed() {
return getBaseSpeed();
class AfricanSwallow extends Bird {
private int _numberOfCoconuts;
public AfricanSwallow() {
this(randomInt(4));
public AfricanSwallow(int numberOfCoconuts) {
_numberOfCoconuts = numberOfCoconuts;
double getAirSpeed() {
return getBaseSpeed() - getLoadFactor() * _numberOfCoconuts;
public double getLoadFactor() {
return randomDouble(3.12);
class NorwegianBlue extends Bird {
private boolean _isNailed;
private double _voltage;
public NorwegianBlue() {
this(randomInt(10)<2, randomDouble(12.0));
public NorwegianBlue(boolean isNailed, double voltage) {
_isNailed = isNailed;
_voltage = voltage;
double getAirSpeed() {
return _isNailed ? 0 : getBaseSpeed(_voltage);
double getBaseSpeed(double voltage) {
return getBaseSpeed() * (1+(voltage/Math.PI));
public class AirSpeedTest
public static void main(String[] args)
System.out.println("EUROPEAN: "+new EuropeanSwallow().getAirSpeed());
System.out.println("AFRICAN: "+new AfricanSwallow().getAirSpeed());
System.out.println("NORWEGIAN_BLUE: "+new NorwegianBlue().getAirSpeed());
}... and the requisite background for the uninitiated [NORWEGIAN_BLUE|http://www.youtube.com/watch?v=4vuW6tQ0218] and [EUROPEAN v AFRICAN|http://www.youtube.com/watch?v=4b4bGAoVR7g].
You have to know these things when you're a King you know.
Cheers. Keith. -
How to track child instances in parent class
I have a **simple** design question about a good way to implement LV OO.
I have a parent class (multiple instances) with a single child class. The parent class needs to keep track of all "active" instances of the child class because some parent methods must be applied to all children. Is there a way for this to happen automatically in LV? I'm not aware of any, so I assume I will have to use some "register" and "unregister" actions for creation and destruction of child class instances. But how do I track them; where do I store the list?
It would be easiest to simply add an array of child class references to the private class data of the parent. However, LV seems to not support this due to "circular referencing". I am not familiar enough with OO, nor it's implementation in LV to know what is a good design approach to accomplish this task.
Any suggestions?What I am trying to do:
I have one or more TCP connections that I am using. The parent class is the TCP connection. The private data for the class is a queue reference. The queue data type is a type def cluster of relevant parameters. The queue has a maximum of 1 element. The reason for this abstraction is that our applications use many TCP connections "simultaneously." As such, we want almost all of the TCP support VIs to be reentrant. This means that we need semaphore action when connection parameters are changed, and we use the queue to achieve this.
The TCP standard guarantees that each message is delivered intact, but does not guarantee message order. Sending large waveforms (or data from a continuously measuring process) requires additional work to ensure that the messages are correctly reordered on the receive end. We created an Ordered Data Stream (ODS) construct to accomplish this. That is the child class. Each TCP connection has 0 or more ODS. Each ODS inherits all the TCP settings from the parent, and can use the parent communication functions. It seems this is a textbook example of the usefulness of inheritance.
However, all good parents are able to keep track of their children. The TCP class needs to be able to track all active ODS instances on that TCP connection. We are struggling with the best method to use for the TCP class to keep track of all ODSs. Adding an array of ODS class instances to the TCP "private data" does not work, due to circular referencing between parent and child classes.
In response to trying a grandparent class:
We tried using a grandparent class. We added an array of grandparent classes, from which the TCP class inherited. The array is actually ODS instances that have been (2X) upcast from ODS to grandparent (more general class) to be stored in the TCP class data. We found that adding the array of grandparent classes to the TCP class created a VI that could not compile when we attempted to place the type def cluster ("class data") on the block diagram of a VI in the TCP class. -
How to Patch Multiple Instances on same oracle home
Hi All
I Have 4 Instances running on server like below
DEVSTAG /opt/oracle/product/10.2.0
DEVUAT /opt/oracle/product/10.2.0
DEVREVT /opt/oracle/product/10.2.0
DEVREG /opt/oracle/product/11.2.0
i want to Apply the patch set 11.1.0.7.1 to DEVUAT & DEVREVT Instances , Can someone please help .. i dont want this patch set applied to DEVSTAG Instance .. how to exclude that Instance from getting patched ?
Thanks in advance .. hope my requirement is clear.Which patch are you referring to ? The database patching tool (opatch) generally applies any database patch to an ORACLE_HOME. You will need to follow the instructions in the README of the patch. If you need to only patch one instance, then you will have to create a dedicated ORACLE_HOME for each database (i.e they will not share database executables). If you share ORACLE_HOME amongst multiple instances, then you will have to patch all of them simultaneously.
HTH
Srini -
Create multiple instances of same class but with unique names
Hi,
I'm creating an IM application in Java.
So far I can click on a user and create a chat session, using my chatWindow class. But this means I can only create one chatWindow class, called 'chat'. How can I get the application to dynamically make new instances of this class with unique names, for examples chatWindowUser1, chatWindowUser2.
Below is some code utlising the Openfire Smack API but hopefully the principle is the clear.
private void chatButtonActionPerformed(java.awt.event.ActionEvent evt) {
int selectedUserIndex = rosterList.getSelectedIndex();
String selectedUser = rostAry[selectedUserIndex].getUser();
System.out.println("Chat with: " + selectedUser);
if (chatBox == null) {
JFrame mainFrame = CommsTestApp.getApplication().getMainFrame();
chatBox = new CommsTestChatBox(mainFrame,conn,selectedUser);
chatBox.setLocationRelativeTo(mainFrame);
CommsTestApp.getApplication().show(chatBox);
}yes, an array would work fine, just realize that by using an array, you're setting an upper bound on the number of windows you can have open.
As for unique names, if you mean unique variable name, you don't need one. The array index serves to uniquely identify each instance. If you mean unique title for the window, set that however you want (username, index in array, randomly generated string, etc.). It's just a property of the window object.
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