Game Object Design Question

Ok, I have a question on the logical design on my game. The game will consist of a world, levels within the world, items, NPC's, and a Player.
I will have NPC's wandering around the world automatically. In order to move, they are obviously going to need to be able to look at the level they are on, and figure out where they want to go.
My question is regarding the acces to the Level object. What is the smartest way to make someNPC.Move(int x, int y) be able to access the Level? Should I write some static methods for the World or Level classes? The only other way I can think of is to pass the World object on to the NPC's upon thier creation and have them store a reference to it...
Thank you all very much,
Michael

My book on Java 1.3 says calling public final methods is fastest (together with calling private methods). public static methods take about twice as long to call but are still pretty fast. Values assume the jit has optimized the method. Calling synchronized methods is very slow. Instead of using synchronized, make sure only one object is making a movement decision at the same time.
I would coordinate movement using the level objects, because unless objects move to a different level, only objects on the same level influence each other's movement (by standing in the way and for example).
Every object in your model will have a position, and I assume part of the position information is the level it is on. You have several co-existing levels. In that case I would make the "level" postion information a reference to the level for direct access and I would make the methods the moving objects use public final (or just final if possible).
Give your objects a reference to the level they are on. If you knew your exact position on the planet but had NO way to know what planet you are on, how would you decide where to move ? It would have to be something like "ok, I don't have any sensory information but I know I exist and I know my exact location. Lets make a step to see what happens. Oh, I still exist. This means I cannot be on the planet where the step would have resulted in a lethal drop. And oh, my position really did change. This helps too. Only 1.000.000.000.000 more planets to exclude by trial and error..."
But Kayaman is right, the World or level needs to have a reference to each moving object too. You need a list of objects in the same area so the moving objects check for collisions, the level can tell them about environment effects that effect them (to all you moving objects inside me, the death star : You are dead because the rebells have blown up my reactor).

Similar Messages

Method design question...and passing object as parameter to webserice

I am new to webservice...one design question
i am writing a webservice to check whether a user is valid user or not. The users are categorized as Member, Admin and Professional. For each user type I have to hit different data source to verify.
I can get this user type as parameter. What is the best approach to define the method?
Having one single method �isValidUser � and all the client web service can always call this method and provide user type or should I define method for each type like isValidMember, isValidAdmin ?
One more thing...in future the requirement may change for professional to have more required field in that case the parameter need to have more attribute. But on client side not much change if I have a single isValidUser method...all they have to do is pass additional values
isValidUser(String username, String usertype, String[] userAttributes){
if usertype == member
call member code
else if usertype = professional
call professional code
else if usertype = admin
call admin code
else
throw error
or
isValidMember(String username, String[] userAttributes){
call member code
One last question, can the parameter be passed as object in web service like USER object.

First of all, here is my code
CREATE OR REPLACE
TYPE USERCONTEXT AS OBJECT
user_login varchar2,
user_id integer,
CONSTRUCTOR FUNCTION USERCONTEXT (
P_LOGIN IN INTEGER
P_ID_ID IN INTEGER
) RETURN SELF AS RESULT
Either your type wont be compiled or this is not the real code..

Design question: methods returning objects

I have a general design question. When, in general (and why), should you have a method alter an object via it's methods but not return the object as opposed to doing the same operation in a method and then return it.
Consider the two below methods which do basically the same thing. When is one desireable over the other, and why?
Cheers--
public void setMyIntField(SomeObject pObj){
pObj.setSomeInt(5);
public SomeObject setMyIntField(SomeObject pObj){
pObj.setSomeInt(5);
return pObj;
}

Let me give a better example:
class FruitWorker{
private void someMethod(){
    HashMap myCitrus = new HashMap();
    HashMap myTropicals = new Hashmap();
    // use my no return obj method
    addFruitProps1(myCitrus,
                   "tartnes",
                   new FruitProperty("very!" ));
    // use my return object method
    myTropicals = addFruitProps2(myCitrus,
                                  "sweetness",
                                   new FruitProperty("little bit" ));
}// end method
private void addFruitProperties1(HashMap pFruitProps,
                                   String pProp
                                   FruitProperty pVal){
    pFruitProps.add( pProp,pVal);
}// end method
private HashMap addFruitProperties2(HashMap pFruitProps,
                                   String pProp
                                   FruitProperty pVal){
    pFruitProps.add( pProp,pVal);
    return pFruitProps;
}// end method
}// end class

Design question: Scheduling a Variable-timeslot Resource

I originally posted this in general java programming, because this seemed like a more high-level design descussion. But now I see some class design questions. Please excuse me if this thread does not belong here (this is my first time using the forum, save answering a couple questions).
Forum,
I am having trouble determining a data structure and applicable algorithm (actually, even more general than the data structure -- the general design to use) for holding a modifiable (but more heavily read/queried than updated), variable-timeslot schedule for a given resource. Here's the situation:
Let's, for explanation purposes, say we're scheduling a school. The school has many resources. A resource is anything that can be reserved for a given event: classroom, gym, basketball, teacher, janitor, etc.
Ok, so maybe the school deal isn't the best example. Let's assume, for the sake of explanation, that classes can be any amount of time in length: 50 minutes, 127 minutes, 4 hours, 3 seconds, etc.
Now, the school has a base operation schedule, e.g. they're open from 8am to 5pm MTWRF and 10am to 2pm on saturday and sunday. Events in the school can only occur during these times, obviously.
Then, each resource has its own base operation schedule, e.g. the gym is open from noon to 5pm MTWRF and noon to 2pm on sat. and sun. The default base operation schedule for any resource is the school which "owns" the resource.
But then there are exceptions to the base operation schedule. The school (and therefore all its resources) are closed on holidays. The gym is closed on the third friday of every month for maintenance, or something like that. There are also exceptions to the available schedule due to reservations. I've implemented reservations as exceptions with a different status code to simplify things a little bit: because the basic idea is that an exception is either an addition to or removal from the scheduleable times of that resource. Each exception (reservation, closed for maintenance, etc) can be an (effectively) unrestricted amount of time.
Ok, enough set up. Somehow I need to be able to "flatten" all this information into a schedule that I can display to the user, query against, and update.
The issue is complicated more by recurring events, but I think I have that handled already and can make a recurring event be transparent from the application point of view. I just need to figure out how to represent this.
This is my current idea, and I don't like it at all:
A TimeSlot object, holding a beginning date and ending date. A data structure that holds list of TimeSlot objects in order by date. I'd probably also hold an index of some sort that maps some constant span of time to a general area in the data structure where times around there can be found, so I avoid O(n) time searching for a given time to find whether or not it is open.
I don't like this idea, because it requires me to call getBeginningDate() and getEndDate() for every single time slot I search.
Anyone have any ideas?

If I am correct, your requirement is to display a schedule, showing the occupancy of a resource (open/closed/used/free and other kind of information) on a time line.
I do not say that your design is incorrect. What I state below is strictly my views and should be treated that way.
I would not go by time-slot, instead, I would go by resource, for instance the gym, the class rooms (identified accordingly), the swimming pool etc. are all resources. Therefore (for the requirements you have specified), I would create a class, lets say "Resource" to represent all the resources. I would recommend two attributes at this stage ("name" & "identifier").
The primary attribute of interest in this case would be a date (starting at 00:00hrs and ending at 24:00hrs.), a span of 24hrs broken to the smallest unit of a minute (seconds really are not very practical here).
I would next encapsulate the availability factor, which represents the concept of availability in a class, for instance "AvailabilityStatus". The recommended attributes would be "date" and "status".
You have mentioned different status, for instance, available, booked, closed, under-maintainance etc. Each of these is a category. Let us say, numbered from 0 to n (where n<128).
The "date" attribute could be a java.util.Date object, representing a date. The "status", is byte array of 1440 elements (one element for each minute of the day). Each element of the byte array is populated by the number designation of the status (i.e, 0,1,2...n etc.), where the numbers represent the status of the minute.
The "Resource" class would carry an attribute of "resourceStatus", an ordered vector of "ResourceStatus" objects.
The object (all the objects) could be populated manually at any time, or the entire process could be automated (that is a separate area).
The problem of representation is over. You could add any number of resources as well as any number of status categories.
This is a simple solution, I do not address the issues of querying this information and rendering the actual schedule, which I believe is straight forward enough.
It is recognized that there are scope for optimizations/design rationalization here, however, this is a simple and effective enough solution.
regards
[email protected]

Design question for database connection in multithreaded socket-server

Dear community,
I am programming a multithreaded socket server. The server creates a new thread for each connection.
The threads and several objects witch are instanced by each thread have to access database-connectivity. Therefore I implemented factory class which administer database connection in a pool. At this point I have a design question.
How should I access the connections from the threads? There are two options:
a) Should I implement in my server class a new method like "getDatabaseConnection" which calls the factory class and returns a pooled connection to the database? In this case each object has to know the server-object and have to call this method in order to get a database connection. That could become very complex as I have to safe a instance of the server object in each object ...
b) Should I develop a static method in my factory class so that each thread could get a database connection by calling the static method of the factory?
Thank you very much for your answer!
Kind regards,
Dak
Message was edited by:
dakger

So your suggestion is to use a static method from a
central class. But those static-methods are not realy
object oriented, are they?There's only one static method, and that's getInstance
If I use singleton pattern, I only create one
instance of the database pooling class in order to
cionfigure it (driver, access data to database and so
on). The threads use than a static method of this
class to get database connection?They use a static method to get the pool instance, getConnection is not static.
Kaj

Workflow design questions: FM vs WF to call FM

Hereu2019s a couple of workflow design questions.
1. We have Workitem 123 that allow user to navigate to a custom transaction TX1. User can make changes in TX1. At save or at user command of TX1, the program will call a FM (FM1) to delete WI 123 and create a new WI to send to a different agent.
Since Workitem 123 is still open and lock, the FM1 cannot delete it immediately, it has to use a DO loop to check if the Workitem 123 is dequeued before performing the WI delete.
Alternative: instead of calling the FM1, the program can raise an event which calls a new workflow, which has 1 step/task/new method which call the FM1. Even with this alternative, the Workitem 123 can still be locked when the new workflowu2019s task/method calls the FM1.
I do not like the alternative, which calls the same FM1 indirectly via a new workflow/step/task/method.
2. When an application object changes, the user exit will call a FMx which is related to workflow. The ABAP developer do not want to call the FMx directly, she wants to raise an event which call a workflow .. step .. task .. method .. FMx indirectly. This way any commit that happens in the FMx will not affect the application objectu2019s COMMIT.
My recommendation is to call the FMx using u2018in Update tasku2019 so that the FMx is only called after the COMMIT of the application object.
Any recommendation?
Amy

Mike,
Yes, in my first design, the TX can 1. raise a terminating event for the existing workitem/workflow and then 2. raise another event to call another workflow. Both 1 and 2 will be in FM1.
Then the design question is: Should the FM1 be called from TX directly or should the TX raise an event to call a new workflow which has 1 step/task, which calls a method in the Business object, and the method calls the FM1?
In my second design question, when an application object changes, the user exit will call a FMx which is related to workflow. The ABAP developer do not want to call the FMx directly, she wants to raise an event which call a workflow, which has 1 step/task, which calls a method, which calls the FMx indirectly. This way any commit that happens in the FMx will not affect the application objectu2019s COMMIT.
My recommendation is either call the FMx using u2018in Update tasku2019 so that the FMx is only called after the COMMIT of the application object or raise an event to call a receiver FM (FMx).
Thanks.
Amy

Business Objects Design Studio

I am working on a report on Business Objects Design Studio,
Please help me out with the below two issues,
1. I want to display user name after Welcome message. The user name should be of the person who is logged into the SAP warehouse currently.
2. The corresponding user should only view those option, reports that he has access to.
Please suggest me the approach to work on this scenario

Thanks Tammy for the reply. I have posted the same question in my second post, that's why I used the same thread.
What I am trying to do is,
I am trying to figure out a web item equivalent to role menu (of Web Application Designer) in Business Objects Design Studio.
Currently we are using BW 3.5 role menu to display BW 7.0 web template links. As SAP will no longer support role menu web item, I have to find a similar alternative, I am trying to look for a similar authorization (role menu) in Design Studio. All this is required so that if one user has access to only 3 reports then he should get only 3 reports displayed in the index page for all reports i.e main page for accessing all reports.
Also, i would greatly appreciate if you could please provide some more inputs on Design Studio Backend authorizations .

BC4J + Struts: Design questions!

OK, I'm wanting to use Struts with BC4J and have a design question for you BC4J users and gurus.
Here's how I think things would work:
1. User requests page
2. Struts ActionServlet calls perform() on Struts ActionForm
3. Struts ActionForm instantiates BC4J AppModule and calls business method
4. BC4J AppModule instantiates necessary BC4J ViewObjects and performs business operations which return data
5. Struts ActionForm receives value objects from BC4J AppModule
6. Struts ActionForm populates Struts FormBean
7. Struts ActionForm forwards to Struts JSP which displays Struts FormBean
I prefixed the components with Struts/BC4J to keep things clear where things belong.
Now, here are my questions:
In step 3, what's the best method of doing this? Do I need to do JNDI lookups every time? What's the performance overhead of this? Anyone have any best-practice code that does this?
Is this the accepted way of doing things? Is there a better way of designing this system?
Thanks!

In Step3 you should use the ApplicationModule pooling framework, especially if you are trying to work in stateful mode because the pooling automatically handle the AM activation/passivation.
There are different way to go at it.
If you are using the BC4J custom tag library and have an ApplicationModule tag in your jsp, the pooling is already initialize. By the time your action is trigger you just need to retrieve the am using the application id:
in your jsp:
<jbo:ApplicationModule id="myAM" ... />
in your Action implementation:
HttpContainer container = HttpContainer.getInstanceFromSession(request.getSession());
SessionCookie cookie = container.getSessionCookie("myAM");
ApplicationModule am = null;
if (cookie != null)
am cookie.useApplicationModule();
This AM id can be passed as URL parameter...
If you do have a JSP with an AM tag you need to create the pool with findSessionCookie call.
For more info about AM pooling look at the end of this thread for Steve resources:
http://forums.oracle.com/forums/message.jsp?id=912431&gid=513211
This is what we are currently doing for to provide support for BC4J in Struts for our next release.
Charles.

Design questions on using JMX

I have been reading about JMX and trying to understand it
I have some specific design realted questions and wanted some opinions to validate my understanding
Assume a simple j2ee application that exposes 2 webservices .
I would like to find out how many times each service is called and the total number of success/faults/errors
encountered for each service along with params like starttime etc
From what I have understood , I will have to first create a Bean , say "StatsCollector"
and then creae a StatsCollectorMBean interface.
The StatsCollector will provide the methods to set/update the above values and those will also be exposed by the StatsCollectorMBean interface
1) I have trouble understanding how to create and maintain the MBean Resource...
Shouldnt there be always 1 instance of this resource ? ie shouldnt there be only one StatsCollector ?
Most of the examples create a simple class "Hello implements HelloMBean" and that makes it a MBean
but they create Hello hello = new Hello() and then register it with the MBean server
What if we create multiple objects of Hello? Wouldnt that defeat the porpose of the MBean ?
I think that we need to make sure that this resource is always created once only.
Is that correct ?
2) Is it the right practice to separate your MBean and your "managed" resource ?
ie in the above case , should there be a Singleton StatsCollector POJO that stores the Appliction
statistics and another StatsMBean that will be the MBean that will access the POJO ? This makes sure that your Resource does not have
dependency management classes.
3) How does the application update the values in the MBean ?
In the above example , how do you update the success and failure counts in the MBean from the application ?
Can I update the singleton StatsCollector directly or do I have to go through the MBean Server to update
any value in the MBean ?
If I update them directly , will they be "visible" thru the MBean server ?
4) Assuming that the above app gets deployed in a appserver like WebSphere and in a Clustered environment ,
how to ensure that statisitcs are collected for all the services on all servers cummulativly ?
Is this something that the appserver should provide ? Do we register the MBean with the Appserver
MBean server ?
Any ideas/suggestions will be helpful !
thanks
Pat

Hello pat,
very interesting questions. You are covering the main JMX design questions there.
You should have a look (if you not already did) to the JMX best practices : http://java.sun.com/javase/technologies/core/mntr-mgmt/javamanagement/best-practices.jsp
This document summarize common JMX design patterns.
Answers to your questions:
1) The resources you want to manage/monitor are Web Services. The life cycle of these services is handled by the J2EE container itself. As you say, the tricky part is to link the WebService resource life cycle to the MBean resource
The MBean leaves inside its own container, the MBeanServer.
You should identify an initialization phase in which you create your MBeans and register them inside the MBeanServer once.
In your case, you can go for a single collector that monitors the 2 Web Services or a collector per Web Service. It seems that you want to track each service independently. Having 2 MBeans should offer a more flexible solution.
If you go for 1 MBean, you should name it "<your management domain>:type=StatsCollector". This name identify an MBean for which you have a single instance. Once the collector registered with this name, the MBeanServer will guarantee that no MBean with the same name can be registered.
If you go for 2 MBeans, you should add the Web Service name to each MBean ObjectName. For example:
MBean 1 : "<your management domain>:type=StatsCollector,name=MyWebService1"
MBean 2 : "<your management domain>:type=StatsCollector,name=MyWebService2"
Example of MBean creation and registration code :
StatsCollector collector1 = new StatsCollector();
ManagementFactory.getPlatformMBeanServer().registerMBean(collector1,
new ObjectName("com.foo.bar:type=StatsCollector,name=WebService1");
At this point you have an MBean registered inside the platform MBeanServer.
2) A Standard MBean is formed of a java interface and a class. Generally the interface and the class are not separated. They could be but I don't see a strong reason in your case to have the POJO and interface not being the same object.
3) You shouldn't expose the methods to set the values in your MBean interface. Only getters should be visible. It means that you will have to keep a direct reference to the collectors to update the statistics. During your initialization phase, you could use JNDI to register the collector instances. The WebServices will then use JNDI to retrieve the collectors.
An example of a simplified StatsCollector class and StatsCollectorMBean interface
public interface StatsCollectorMBean {
public int getNumRequests();
public class StatsCollector implements StatsCollectorMBean {
private int numRequests.
public int getNumRequests() {
return average;
public serviceCalled() {
numRequests++;
In the above example, serviceCalled is not part of the management interface and is called by the Web Service.
4) Difficult question for which I can't provide you with a reply. JMX doesn't offer such cumulative service in a standard way. In some appserver (glassfish for instance), MBeans are cascaded inside the domain server. There is no cumulative representation offered, but you could implement your own by defining new MBeans linked to the StatsCollector ones.
To conclude, Appservers are offering some "out of the box" management and monitoring features . For example glassfish relies on the AMX framework (that is JMX based) . AMX (https://glassfish.dev.java.net/javaee5/amx/) allows you to monitor and manage your services. A possible solution would be to rely on this infrastructure to build your own management and monitoring.
Hope this help.
Regards.
Jean-Francois Denise

Database Connection design question

Hello, I have a design question. Awhile back I needed to create a database connection to SQL Server, so I created a class to do it
import java.sql.*;
import java.io.*;
import java.net.MalformedURLException;
import org.w3c.dom.Document;
import org.w3c.dom.*;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
public class SQLServerConnection
     private static Connection connection = null;
     public SQLServerConnection(String user, String password, String dbName) throws java.sql.SQLException
          getDBConnection(user, password, dbName);
     public SQLServerConnection(String configFileName) throws java.sql.SQLException
          getDBConnection(configFileName);
     private void getDBConnection(String user, String password, String dbName) throws java.sql.SQLException
         DriverManager.registerDriver(new com.microsoft.jdbc.sqlserver.SQLServerDriver());
         connection = DriverManager.getConnection(
              "jdbc:microsoft:sqlserver:" + dbName, user, password);
     private void getDBConnection(String configFileName) throws java.sql.SQLException
          String user;
          String password;
          String dbName;
          try
               DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
               DocumentBuilder db = factory.newDocumentBuilder();
               Document doc = db.parse(configFileName);
               doc.getDocumentElement().normalize();
               // get the configuration information
               password = getConfigParameter("password", doc);
               user = getConfigParameter("username", doc);
               dbName = getConfigParameter("databasename", doc);
               getDBConnection(user, password, dbName);
          catch (MalformedURLException murle)
               System.out.println("Unable to connect to: " + configFileName + " -- " + murle);
               System.exit(1);
          catch (FileNotFoundException fnfe)
               System.out.println("Configuration file " + configFileName + " not found.");
               System.exit(1);
          catch (IOException ioe)
               System.out.println("IOException: " + ioe);
               System.exit(1);
          catch (javax.xml.parsers.ParserConfigurationException pce)
               System.out.println ("Parser Configuration Error: " + pce);
          catch (SAXException saxe)
               System.out.println ("SAXException: " + saxe);
     private String getConfigParameter(String paramName, org.w3c.dom.Document doc)
          NodeList nl = doc.getElementsByTagName(paramName);
          if(nl != null)
               Node n = null;
               for (int i = 0; i < nl.getLength(); i++)
                    n = nl.item(i);
                    if(n.hasChildNodes())
                         NodeList children = n.getChildNodes();
                         return ((Node)children.item(0)).getNodeValue();
          else
               System.out.println ("nl is null");
          return "";
     public void setCatalog(String catalogName) throws java.sql.SQLException
          connection.setCatalog(catalogName);
     public Connection getConnection()
          return connection;
     public void closeConnection()
          try
               connection.close();
          catch(java.sql.SQLException sqle)
               System.err.println ("SQL Server Connection failed to close: " + sqle);
}Later on, I needed to do the same thing for MySQL, so I created a class for that, MySQLServerConnection which is exactly the same as above, except for:
private void getDBConnection(String user, String password, String dbName) throws java.sql.SQLException
          try
               Class.forName("com.mysql.jdbc.Driver").newInstance();
               connection = DriverManager.getConnection(dbName, user, password);
          catch(java.lang.ClassNotFoundException cnfe)
               System.out.println (cnfe);
          catch(java.lang.InstantiationException ie)
               System.out.println (ie);
          catch(java.lang.IllegalAccessException iae)
               System.out.println (iae);
     }Later, on, I did the same thing with OracleServerConnection. My question is, I know this is probably not optimal code. For example, I didn't originally have a close connection method, so I had to go in and code one for all 3. I'm assuming that an interface would be a good idea so that if I have to code another database connection class I make sure and include all of the appropriate methods. I'm also assuming that it would have been smart to have a master class, maybe something like DatabaseConnection and extended these classes from that. Am I on the right track? Totally offbase?

@nclow - I will work on trying the Factory Pattern for this over the weekend and post when I finish to see what you think.
@abillconsl - just to make sure I understand, you're saying that I just try to connect and it will cycle through the different database connection possibilities and connect when it finds the right one? If it fails all 3, log an appropriate message. One question I have about this is, I thought I was being object oriented by separating the different types of db connections (Oracle, SQL Server, MySql) into different classes. Am I missing the point of OOP by what I was/am trying to accomplish? Going overboard? Also, does your way try and connect to all 3 even if I connected to one already?
Thx, Grantarchy
Edited by: grantarchy on May 9, 2008 9:50 PM

Design Question: Parent/Child Distribution

Hi,
I have what I think is a straightforward design question. I tried
searching this forum for the answer, but struggled with what keywords
to use in the searches. (I also struggled with what to put on the
subject line for this post!)
Anyhow, here is my question: Given:
public class Pet {...}
public class Dog extends Pet {...}
public class Cat extends Pet {...}
public class Pig extends Pet {...}
Which is the better design?
DESIGN A:
public abstract class PetOwner {
private Pet pet;
PetOwner(Pet pet) {
this.pet = pet;
public Pet getPet() { return this.pet; }
public class DogOwner extends PetOwner {
public DogOwner(Dog dog) {
super(dog);
public class CatOwner extends PetOwner {
public CatOwner(Cat cat) {
super(cat);
public class PigOwner extends PetOwner {
public PigOwner(Pig pig) {
super(pig);
===============================================
or DESIGN B:
public abstract class PetOwner {
PetOwner() {
public class DogOwner extends PetOwner {
private Dog dog;
public DogOwner(Dog dog) {
super();
this.dog = dog;
public class CatOwner extends PetOwner {
private Cat cat;
public CatOwner(Cat cat) {
super();
this.cat = cat;
public class PigOwner extends PetOwner {
private Pig pig;
public PigOwner(Pig pig) {
super();
this.pig = pig;
This is a somewhat contrived example, so don't take it too literally.
My question is where should I put the field that holds a Pet object?
All pet owners own a pet, so should I put it in the parent class
(Design A)? Note the constructors for the child classes (e.g.
DogOwner) are designed so that the correct type of pet is checked
for. Or should each child class hold its own type of pet (Design B)?
If the answer is "it depends" (as I suspect it is), then what are
the questions I should be asking myself in order to decide?
Thanks very much, in advance!!
Chris

eg,
import java.util.*;
class Pet {
    private String name = null;
    public Pet( String n ) {
     this.name = n;
    public String toString() {
     return name;
class Dog extends Pet {
    public Dog( String n ) {
     super( n );
class Pig extends Pet {
    public Pig( String n ) {
     super( n );
class Cat extends Pet {
    public Cat( String n ) {
     super( n );
class PetOwner {
    private Vector pets = new Vector();
    private int dogs = 0;
    private int cats = 0;
    private int pigs = 0;
    public void add( Dog d ) {
     pets.add( d );
     dogs++;
    public void add( Cat c ) {
     pets.add( c );
     cats++;
    public void add( Pig p ) {
     pets.add( p );
     pigs++;
    public boolean isCatOwner() {
     return cats > 0;
    public boolean isDogOwner() {
     return dogs > 0;
    public boolean isPigOwner() {
     return pigs > 0;
    public int numberOfPets() {
     return pets.size();
    public String toString() {
     String s = "";
     Enumeration en = pets.elements();
     while( en.hasMoreElements() ) {
         Pet pp = (Pet) en.nextElement();
         s += pp.toString() + "\n";
     return s;
public class Pets {
    private PetOwner po = new PetOwner();
    public Pets() {
     po.add( new Dog( "doggy" ) );
     po.add( new Cat( "catty" ) );
    public String toString() {
     String s = "";
     s += po.toString();
     s += po.isDogOwner() + "\n";
     s += po.isPigOwner() + "\n";
     s += po.isCatOwner() + "\n";
     s += po.numberOfPets();
     return s;
    public static void main( String[] args ) {
     Pets p = new Pets();
     System.out.println( p );
}

Design question about when to use inner classes for models

This is a general design question about when to use inner classes or separate classes when dealing with table models and such. Typically I'd want to have everything related to a table within one classes, but looking at some tutorials that teach how to add a button to a table I'm finding that you have to implement quite a sophisticated tablemodel which, if nothing else, is somewhat unweildy to put as an inner class.
The tutorial I'm following in particular is this one:
http://www.devx.com/getHelpOn/10MinuteSolution/20425
I was just wondering if somebody can give me their personal opinion as to when they would place that abstracttablemodel into a separate class and when they would just have it as an inner class. I guess re-usability is one consideration, but just wanted to get some good design suggestions.

It's funny that you mention that because I was comparing how the example I linked to above creates a usable button in the table and how you implemented it in another thread where you used a ButtonColumn object. I was trying to compare both implementations, but being a newbie at this, they seemed entirely different from each other. The way I understand it with the example above is that it creates a TableRenderer which should be able to render any component object, then it sets the defaultRenderer to the default and JButton.Class' renderer to that custom renderer. I don't totally understand your design in the thread
http://forum.java.sun.com/thread.jspa?forumID=57&threadID=680674
quite yet, but it's implemented in quite a bit different way. Like I was saying the buttonClass that you created seem to be creating an object of which function I don't quite see. It looks more like a method, but I'm still trying to see how you did it, since it obviously worked.
Man adding a button to a table is much more difficult than I imagined.
Message was edited by:
deadseasquirrels

LDAP design question for multiple sites

LDAP design question for multiple sites
I'm planning to implement the Sun Java System Directory Server 5.2 2005Q1 for replacing the NIS.
Currently we have 3 sites with different NIS domains.
Since the NFS over the WAN connection is very unreliable, I would like to implement as follows:
1. 3 LDAP servers + replica for each sites.
2. Single username and password for every end user cross those 3 sites.
3. Different auto_master, auto_home and auto_local maps for three sites. So when user login to different site, the password is the same but the home directory is different (local).
So the questions are
1. Should I need to have 3 domains for LDAP?
2. If yes for question 1, then how can I keep the username password sync for three domains? If no for question 1, then what is the DIT (Directory Infrastructure Tree) or directory structure I should use?
3. How to make auto map work on LDAP as well as mount local home directory?
I really appreciate that some LDAP experta can light me up on this project.

Thanks for your information.
My current environment has 3 sites with 3 different NIS domainname: SiteA: A.com, SiteB:B.A.com, SiteC:C.A.com (A.com is our company domainname).
So everytime I add a new user account and I need to create on three NIS domains separately. Also, the password is out of sync if user change the password on one site.
I would like to migrate NIS to LDAP.
I want to have single username and password for each user on 3 sites. However, the home directory is on local NFS filer.
Say for userA, his home directory is /user/userA in passwd file/map. On location X, his home directory will mount FilerX:/vol/user/userA,
On location Y, userA's home directory will mount FilerY:/vol/user/userA.
So the mount drive is determined by auto_user map in NIS.
In other words, there will be 3 different auto_user maps in 3 different LDAP servers.
So userA login hostX in location X will mount home directory on local FilerX, and login hostY in location Y will mount home directory on local FilerY.
But the username and password will be the same on three sites.
That'd my goal.
Some LDAP expert suggest me the MMR (Multiple-Master-Replication). But I still no quite sure how to do MMR.
It would be appreciated if some LDAP guru can give me some guideline at start point.
Best wishes

SOA real-time design question

Hi All,
We are currently working with SOA Suite 11.1.1.4. I have a SOA application requirement to receive real-time feed for six data tables from an external third party. The implementation consists of five one-way operations in the WSDL to populate the six database tables.
I have a design question. The organization plans to use this data across various departments which requires to replicate or supply the data to other internal databases.
In my understanding there are two options
1) Within the SOA application fork the data hitting the web-service to different databases.
My concern with this approach is what if organizations keep coming with such requests and I keep forking and supplying multiple internal databases with the same data. This feed has to be real-time, too much forking with impact the performance and create unwanted dependencies for this critical link for data supply.2) I could tell other internal projects to get the data from the populated main database.
My concern here is that firstly the data is pushed into this database flat without any constraints and it is difficult to query to get specific data. This design has been purposely put in place to facilitate real-time performance.Also asking every internal projects to get data from main database will affect its performance.
Please suggest which approach should I take (advantage/disadvantage. Apart from the above two solutions, is there any other recommended solution to mitigate the risks. This link between our organization and external party is somewhat like a lifeline for BAU, so certainly don't want to create more dependencies and overhead.
Thanks

I had tried implementing the JMS publisher/subscriber pattern before, unfortunately I experienced performance was not so good compared to the directly writing to the db adapter. I feel the organization SOA infrastructure is not setup correctly to cope with the number of messages coming through from external third party. Our current setup consists of three WebLogic Servers (Admin, SOA, BAM) all running on only 8GB physical RAM on one machine. Is there Oracle guideline for setting up infrastructure for a SOA application receiving roughly 600000 messages a day. I am using SOA 11.1.1.4. JMS publisher/subscriber pattern just does not cope and I see significant performance lag after few hours of running. The JMS server used was WebLogic JMS
Thanks
Edited by: user5108636 on Jun 13, 2011 4:19 PM
Edited by: user5108636 on Jun 13, 2011 7:03 PM

Aggregation level - design question

Hi, All
we are in BI-IP ( Netweaver 2004s SPS16).
I have a design question for this scenario.
User needs to plan the amounts for a duration (start period and end period), Jan2008 -Dec2008 (001.2008, 012.2008) = 12000.
We need to distribute this to the periods equally. 001.2008 = 1000, 002.2008 =1000 .... 012.2008=1000.
If the user changes the period amounts, it should be reflected back in the duration amount.
Pl suggest the design for the aggregation levels to achieve this.
Thanks in advance.
velu

Hello Velu,
As the name also goes, creating an "aggregation level" will only result in "aggregation". What your requirement is, is called disaggregation or distribution - this cannot happen automatically - you will either have to use the feature in input queries or use the distribution planning function or create your own planning function using fox/exit.

Game Object Design Question

Similar Messages

Maybe you are looking for