Calling instance variable...

Hi,
Just wondeirng if I defined some instance variables in a class. If I want to call the variables in another class. Is it like <class_of_variables_are_defined>.<variables> ?

Here are the codes I have written...I am still having a little trouble though
Variables that I have defined in two different class...
Ride.class
public class Ride
     private String name;
     private int ticketsRequired, numberOfRiders;
     private float heightRequirement;
     public String getName()
          return name;
     public int getTicketsRequired()
          return ticketsRequired;
     public int getNumberOfRiders()
          return numberOfRiders;
     public float getHeightRequirement()
          return heightRequirement;
TicketBooth.class
public class TicketBooth
     private float moneyMade;
     private int availablePasses;
     public float TICKET_PRICE = 0.5f;
     public float PASS_PRICE = 16.5f;
     public float getMoneyMade()
          return moneyMade;
     public int getAvailablePasses()
          return availablePasses;
     public TicketBooth(int initAvailablePasses)
          availablePasses = initAvailablePasses;
                     .....Now when I try to use those private instance variables in Person.class, I got bunch of errors. I know private instances can only be used within the class they defined. How should I correct the code below?
Person.class
                     public boolean buyPass(TicketBooth booth)
          if (hasPass == true && money >= PASS_PRICE)
               return true;
          else
               return false;
     public boolean allowedToRide(Ride aRide)
          if (height >= heightRequirement &&
             (hasPass == true || ticketCount >= ticketRequired))
               return true;
          else
               return false;
     public void getOn(Ride aRide)
          if ((allowedToRide(aRide) == true) && (hasPass == true))
               availablePasses -= 1;
               numberOfRiders += 1;
          else if(ticketCount >= ticketRequired)
               numberOfRiders += 1;
               ticketCount -= ticketsRequired;
                     .......

Similar Messages

Stateless Bean - scope of instance variable in EJB Timer call back function

Hi,
I would like to know on the scope of an instance variable of a Stateless Bean object,
when used in a EJB Timer call back.Let me explain this in more detail below.
I have a requirement to use a EJB Timer.
For this, I have created a stateless object since Timer creation needs to be done
from a stateless bean. I have a member variable "count" of the stateless bean class.
In the timer call back(ejbTimeout), I am able to use this count variable during
each time of the call back, and the value of this variable is also updated properly.
I have a few queries with respect to the above behaviour:
1) Does stateless bean object not get destroyed once the Timer is created from the Bean?
2) If the Bean object is not destroyed, then when does the bean object get destroyed?
3) If both (1) and (2) are not true, then can anyone explain on how the above behaviour is possible?
Thanks in advance,
Ulrich

Hi Ulrich,
The ejb timer is associated with the stateless session bean component, not with a particular bean instance. There is no formal relationship between the bean instance that called createTimer() and the bean instance on which the timer callback happens. If they're the same in your test run that's just a coincidence and not something your application should be depending on.
In the stateless session bean model, the container can create and destroy stateless session bean instances at any time. The container is free to pick any stateless session bean instance to service any client invocation or timer callback. If you need to pass context into a timer callback, one way to do it is via the timer "info" object. However, the info object is immutable so it wouldn't be a good match for a counter. You could of course always just use a database for any necessary coordinated state.
--ken

Persisting Instance Variables in Object Types across PL/SQL Calls

How can I persist instance variables in my java class/object across PL/SQL calls via a PL/SQL object type.
What I am finding is that if I do not have an attribute defined in my PL/SQL datatype that the value is not persisted between calls on the object in the PL/SQL environment. I am using the SQLData interface.
Should I create a static variable that uses the singleton pattern?
Any insights appreciated.

How can I persist instance variables in my java class/object across PL/SQL calls via a PL/SQL object type.
What I am finding is that if I do not have an attribute defined in my PL/SQL datatype that the value is not persisted between calls on the object in the PL/SQL environment. I am using the SQLData interface.
Should I create a static variable that uses the singleton pattern?
Any insights appreciated.

How to use an BPM Instance Variable in JSP page

Hi All,
I am using the JSP Presentation, but i don't know how to use an Instance variable in JSP page, that instance already declared in the process. And Can u explain the syntax that to include the JS file into jsp page
Regards
Vasu.
Edited by bpmvasu at 04/03/2007 10:43 PM

Hi Mariano,
I'm using JSP presentation too. In "Interactive Component Call" active i'm using "Use JSP presentation", but i only can define one instance variable, i need to add more instance variables. In "Advanced" option of this task, i have the argument mapping .. but i don't understand how to use it.
I have a instance variable called "genders" of the type String[Int] (Associative Array) and i'm mapping this instance variable in "Arguments Show In" option of the advanced option of JSP presentation. In JSP presentation i have the code:
<select <f:fieldName att="person.gender"/>>
               <c:forEach var="gender" begin="0" items="${genders}" varStatus="status">
                    <c:choose>
                         <c:when test="${person.gender == gender}">
                              <option value="<c:out value="${gender}"/>" selected="true"><c:out value="${gender}"/></option>
                         </c:when>
                         <c:otherwise>
                              <option value="<c:out value="${gender}"/>"><c:out value="${gender}"/></option>
                         </c:otherwise>
                    </c:choose>
               </c:forEach>
          </select>And in my screenflow i have the code:
genders[0] = "Male"
genders[1] = "Female"But when i run my application, i have the error: "The task could not be successfully executed. Reason: 'java.lang.ClassCastException: java.lang.Integer'."
What's the problem?

How can I use evaluate to get the instance variable in customized tag

1.
At first , I create a class called bean,and declared several params in it and do not define any getter function for the param.
class bean{
String param = "test";
SomeClass scObj = new SomeClass();
2.
The second ,I use
request.setAttribute("beanObj",new bean());
3.
And then I wanna use the customized tag to show a text box , then initialize it's value.
<salt:text name="param" value="beanObj.param">
<salt:text name="obj" value="beanObj.scObj.func()">
4.
I tried the evaluator provided by JexlContext ,Struts, JSTL and it seems that if I do not define the getter for the variable ,I can not get the bean's instance variable's value.
Expression e = ExpressionFactory.createExpression( value );
JexlContext jc = JexlHelper.createContext();
jc.getVars().put(strInitBeanName, request.getAttribute("beanObj"));
Object obj = e.evaluate(jc);
the result of the obj is null....
Can anybody recommand some other evaluator can get the value of a instance variable from an object?

do you have any other suggestion ? Nops, somebody else may have though. AFAIK, all lookups of the type
beanName.propertyNameuse reflection on the getXXX() methods to access the property.
Having said that, I guess you could write one though in a custom tag, using the same - reflection (you will ahve to rely on the java.lang.reflect.Field class quite heavily) - but that would be reinventing the wheel for most other functionality that you would have to include (like looking up the bean in scope etc)
cheers,
ram.

Binding: Instance variable loses value.

Hi all,
Just making my first steps into Objective-C, I've done a lot of C, C++ and C# on win & linux. Anyhow, I've been hacking away happily and discovered a peculiar behaviour, and I'm not sure if it's my code or some obscure bug in Xcode.
1. I have a Check Box(NSButton) directly bound to a BOOL instance variable called "checkValue" using KVC. The containing class is a custom NSView subclass.
2. I manually implemented the setter according to KVC naming rules "setCheckValue".
3. When debugging the UI (check box) calls the setter perfectly with the correct value, which shows up in the NSLog output.
4. I hooked up the action for the check box as well, and inside the action handler the instance variable reports the value correctly. Everything looks fine.
5. Now here's the rub. I put a mousedown event handler into the class as well, and it is called flawlessly when I click on the custom view. However, "checkValue" does not report the correctly set value.
So, how can a class instance variable, which is set and reports correctly elsewhere in the same scope, all of the sudden take on a nonsense value in a event handler? If a variable has a value set, it should be the same everywhere within the same scope!
Below is simplified code extracted from the original project for clarity. It produces exactly the same behaviour as the more complex project without the distracting code.
#import "CheckBoxHandler.h"
@implementation CheckBoxHandler
@synthesize checkValue;
//Apparently this is required for binding in NSView based classes
//The same behaviour occurs even if you remove this.
+(void)initialize
[self exposeBinding:@"checkValue"];
-(id)initWithFrame:(NSRect)frameRect
self = [super initWithFrame:frameRect];
if(!self)
return nil;
[self setCheckValue:YES];
return self;
//manual impelementation of KVC setter
-(void)setCheckValue:(BOOL)v
checkValue = v;
NSLog(@"Setter Called: checkValue is %d", checkValue);
//The action works fine as evidenced by Log output
//Check and uncheck the box a few times.
-(IBAction)checkBoxAction:(id)sender
NSLog(@"UI State:%d Ivar State: %d", [checkBox state], checkValue);
//Mouse clicking on the view calls into this event.
//The problem is the value reported by [self checkValue] OR checkValue directly
//do not match the UI state. In fact it always reports some nonsense value.
-(void)mouseDown:(NSEvent *)event
NSLog(@"Inside Mousedown: checkValue is: %d", [self checkValue]);
@end
I have a workaround, but it really bends my head when something doesn't behave as expected!

I have synthesized against "checkValue", although I manually implemented the setter so I could set a breakpoint and observe the value. I thought [self checkValue] and self.checkValue both simply call the same getter, just different syntax.
The setting of the value using the UI checkbox happens outside of the event call chain. I can check and uncheck the checkbox and the value changes correctly. The checkbox is in a separate space on the window, so clicking it does not activate mousedown on the view, this is correct behaviour. Clicking on the view does activate the mousedown event, this is done after I've set the checkbox so the value has been set well before the mousedown event. Thus it should already have the correct value in the event.
For completeness this is the interface file:
#import <Cocoa/Cocoa.h>
@interface CheckBoxHandler : NSView {
IBOutlet NSButton *checkBox;
BOOL checkValue;
-(IBAction)checkBoxAction:(id)sender;
@property (assign, readwrite) BOOL checkValue;
@end
I'll change everything to self.checkValue just for the excercise. Ok, done. checkValue still reports a value of 1 in the mousedown event regardless of the value set elsewhere.

JSP and Instance Variables

I have some questions about JSP presentation (Interactive Component Call in Screenflow):
- Only BPM Objects are possible to be mapped in JSP?
- Is possible to map two or more BPM Objects to the JSP?
- What is the difference of mapping using the variable "attributes" in argument mapping and the option "Select BPM object variable" in main task of Interactive Component Call activity?

I seem to be having a similar problem.
If I include this fragment, for an instance variable called "contacts" which is a BPMObject of type "ITSSContactRequest".
<%
Object r = request.getAttribute("contacts");
Class cl = r.getClass();
out.println(cl.getName());
%>
I get the following output:
xobject.ITSSContactManagement.ITSSContactRequest
and I can access the object via reflection:
<%
Object r = request.getAttribute("contacts");
Class cl = r.getClass();
out.println(cl.getName());
Method getGeneralContacts = cl.getMethod("getGeneralContacts", null);
Object rv = getGeneralContacts.invoke(r);
%>
and access the rv variable accordingly.
However, if I try and cast the variable directly:
<%
Object r = request.getAttribute("contacts");
Class cl = r.getClass();
out.println(cl.getName());
xobject.ITSSContactManagement.ITSSContactRequest rq = (xobject.ITSSContactManagement.ITSSContactRequest)r;
%>
I get the following error message:
"The task could not be successfully executed. Reason: 'fuego.web.execution.exception.InternalForwardException: UnExpected error during internal forward process.'.
See log file for more information [Error code: workspace-1258985548580] "
The same error occurs if I try and import the object via
<%@ page import="xobject.ITSSContactManagement.ITSSContactRequest" %>
Thanks for any help.

Null Instance Variables on Screenflow

Hi,
I have some problems with instance variable of type BPM Objects in a Screenflow.
I always create automatic processes without user interaction, and on server side I have seen that it's not necessary to instantiate an instance variable. Moreover if within a method I write (I use the Java style syntax):
String a;
a.toString(); // just to call a method on a not-instantiated variable
everything works correctly, the "a" variable is automatically instantiated.
But it seems that in an automatic activity of a Screenflow it's different, I need to do the new also for Instance Variables.
Then, in the Screenflow I have an Instance Variable myObject of type MyObject that is a BPM Object. This object has an attribute myStrings that is an array of String.
To instantiate the instance variable I can write:
myObject = new MyObject();
But then I get a java.lang.*NullPointerException* when I call the extend method of its attribute myStrings to add a string.
Do you agree with me that on the Screenflow code it's necessary to instantiate the variables?
How can I instantiate an Array of String?
Thank you.

Thanks Daniel, I'm using ALBPM 6.0,
i know the line where I get the exception, I have a logMessage before and after each line of code, and then in the exception stack there is the PBL Method line indicated:
Caused by: java.lang.NullPointerException
at xobject.Fuego__AutoGen__Screenflows__.__ScreenflowConJsp.automatic1(__ScreenflowConJsp.xcdl:*19*)
19 is the code line where I get the exception. In this line I have this:
myObject.myStrings.extend(arg1 : a);
but the null object is not the array, it's myObject that is an Instance Variable.
In ALBPM60_Studio_ReferenceGuide at chapter Programming Styles paragraph Java Programming Style there is:
This style emulates Java syntax and adds several features to match PBL expressions. These added features include:
• Output arguments
• Input and display statements
• Variable auto-initialization
In fact in my previuos BPM projects I have seen that is not necessary to istantiate the variables, both for Instance Variable and local variable declared within a method. In my previous post I did an example:
String a;
a.toString();
Usually this causes an Exception, but not in ALBPM methods.
My main question is: is it possible that this is true just for Server side methods and not for Screenflow methods? Because in my case I need to instantiate every Instance Variable of my Screenflow (for example the myObject instance variable) in an Automatic Activity I have put as first Activity of the flow.
Thanks again for your help.

How to invoke BPM object instance variable from interactive activity?

I have a screenflow with an automatic activity "A" followed by an interactive activity "B". "B" calls a BPM object "X" and uses a JSP presentation to show its attributes. Is there a way to use another BPM object, say type "Y", create an instance variable of that type inside "A", and get its attributes values from the JSP page associated to "B"?
Edited by: user6473912 on 20/07/2010 03:37 PM

Try this. It assumes you have:
<li> a user named "auto"
<li> a project variable named "customerType"
<li> an instance variable named "orderAmount" that is a decimal
<li> an instance variable named "order" that is a BPM Object that has attributes named "customerName" and "amount"
ps as ProcessService
xmlObject as Fuego.Xml.XMLObject
do
connectTo ps
      using url = Fuego.Server.directoryURL,
      user = "auto",
      password = "auto"
instF as InstanceFilter
create(instF, processService : ps)
addAttributeTo(instF, variable : "customerType", comparator : IS, value : "Gold")
instF.searchScope = SearchScope(participantScope : ParticipantScope.ALL, statusScope : StatusScope.ONLY_INPROCESS)
for each inst in getInstancesByFilter(ps, filter : instF) do
    // here's how to get the value inside a primitive instance variable
    orderAmtObj as Object = getVar(inst, var : "orderAmount")
    // here's how to get the value of attributes inside a complex BPM Object instance variable
    //    - in this case this is an "order" object with two attributes (customerName and amount)
    orderObj as Object = (getVar(inst, var : "order"))
    xmlObject = Fuego.Xml.XMLObject(createXmlTextFor(DynamicXml, object : orderObj, topLevelTag : "xsi"))
    logMessage "The value of the order object's customer name is: " +
           selectString(xmlObject, xpath : "customerName")
    logMessage "The value of the order object's order amount is: " +
           selectNumber(xmlObject, xpath : "amount")
    // here's a rather uninspired way to retrieve who the participant is that was assigned the instance
    logMessage "The participant assigned to this instance is: " + inst.participantId
end
on exit
disconnectFrom ps
endDan

Binding a JavaFX variable to a Java class instance variable

Hi,
I am pretty new to JavaFX but have been developing in Java for many years. I am trying to develop a JavaFX webservice client. What I am doing is creating a basic scene that displays the data values that I am polling with a Java class that extends Thread. The Java class is reading temperature and voltage from a remote server and storing the response in an instance variable. I would like to bind a JavaFx variable to the Java class instance variable so that I can display the values whenever they change.
var conn: WebserviceConnection; // Java class that extends Thread
var response: WebserviceResponse;
try {
conn = new WebserviceConnection("some_url");
conn.start();
Thread.sleep(10000);
} catch (e:Exception) {
e.printStackTrace();
def bindTemp = bind conn.getResponse().getTemperature();
def bindVolt = bind conn.getResponse().getVoltage();
The WebserviceConnection class is opening a socket connection and reading some data in a separate thread. A regular socket connection is used because the server is not using HTTP.
When I run the application, the bindTemp and bindVolt are not updated whenever new data values are received.
Am I missing something with how bind works? Can I do what I want to do with 'bind'. I basically want to run a separate thread to retrieve data and want my UI to be updated when the data changes.
Is there a better way to do this than the way I am trying to do it?
Thanks for any help in advance.
-Richard

Hi,
If you don't want to constantly poll for value change, you can use the observer design pattern, but you need to modify the classes that serve the values to javafx.
Heres a simple example:
The Thread which updates a value in every second:
// TimeServer.java
public class TimeServer extends Thread {
    private boolean interrupted = false;
    public ValueObject valueObject = new ValueObject();
    @Override
    public void run() {
        while (!interrupted) {
            try {
                valueObject.setValue(Long.toString(System.currentTimeMillis()));
                sleep(1000);
            } catch (InterruptedException ex) {
                interrupted = true;
}The ValueObject class which contains the values we want to bind in javafx:
// ValueObject.java
import java.util.Observable;
public class ValueObject extends Observable {
    private String value;
    public String getValue() {
        return this.value;
    public void setValue(String value) {
        this.value = value;
        fireNotify();
    private void fireNotify() {
        setChanged();
        notifyObservers();
}We also need an adapter class in JFX so we can use bind:
// ValueObjectAdapter.fx
import java.util.Observer;
import java.util.Observable;
public class ValueObjectAdapter extends Observer {
    public-read var value : String;
    public var valueObject : ValueObject
        on replace { valueObject.addObserver(this)}
    override function update(observable: Observable, arg: Object) {
         // We need to run every code in the JFX EDT
         // do not change if the update method can be called outside the Event Dispatch Thread!
         FX.deferAction(
             function(): Void {
                value = valueObject.getValue();
}And finally the main JFX code which displays the canging value:
// Main.fx
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.text.Text;
import javafx.scene.text.Font;
import threadbindfx.TimeServer;
var timeServer : TimeServer;
var valueObjectAdapter : ValueObjectAdapter = new ValueObjectAdapter();
timeServer = new TimeServer();
valueObjectAdapter.valueObject = timeServer.valueObject;
timeServer.start();
Stage {
    title: "Time Application"
    width: 250
    height: 80
    scene: Scene {
        content: Text {
            font : Font {
                size : 24
            x : 10, y : 30
            content: bind valueObjectAdapter.value;
}This approach uses less cpu time than constant polling, and changes aren't dependent on the polling interval.
However this cannot be applied to code which you cannot change obviously.
I hope this helps.

Stateful session bean destroying instance variables?

I'm trying to use a stateful session bean as some kind of login controller and to maintain the login id and access level across JSPs and HTMLs so that once logged in, all the JSPs can obtain the login name of the current user (String) and his access level (int).
I use the login.jsp to login and it successfully reports logging in with the correct access level retrieved from database. However, if I go to another JSP (testlogin.jsp), these 2 EJB instance variables are always destroyed and set to null and 0 when I access them again.
What am I missing that my stateful session bean is not saving these instance variables? Do I need to put them in some serializable value objects (create a help VO class?)
I suspected that on different JSP, I call the MemberControllerHome.create() method, it creates a new instance or something but if I don't use the create method how do I get a handle to MemberController at all?
MemberControllerBean.java
public class MemberControllerBean implements SessionBean {
     //initialize in ejbCreate.
     private MemberHome memberHome;
     SessionContext context;
     //Member currentLogin;
     //Current Login
     private String loginID;
     private int accessLevel;
     // Constructor
     public MemberControllerBean() {}
...some code in between...
public void login(String id, String password){
          try{
               Member member = null;
               member = memberHome.findByPrimaryKey(id);
               if(member.getMPassword().equals(password)){
                    this.loginID = member.getMID();
                    this.accessLevel = member.getMAccessLevel();
               else{
                    throw new EJBException("Login failed. Invalid member ID and/or password.");
          } catch (FinderException ex) {
               throw new EJBException("Login failed. Invalid member ID and/or password.");
     public void logout(){
          this.loginID = null;
          this.accessLevel = 4;
     public String getLoginID(){
          return this.loginID;
     public int getLoginAccessLevel(){
          return this.accessLevel;
login.jsp
String mID = request.getParameter("mID");
String mPassword = request.getParameter("mPassword");
out.println("20:" + mID + ":" + mPassword);
if(mID != null && mPassword != null){
     out.println("22:" + mID + ":" + mPassword);
     try{
          InitialContext ic = new InitialContext();
          MemberControllerHome home = (MemberControllerHome) ic.lookup("java:comp/env/ejb/MemberController");
          MemberController mc = home.create();
          out.println("26:Logging in as " + mID + " with " + mPassword);
          mc.login(mID, mPassword);
          out.println("28:" + mc.getLoginID() + "logged in successfully at level " +
               mc.getLoginAccessLevel() + ".");
     } catch (NamingException ex) {
          out.println("java:comp/env/ejb/MemberController not found.");
     } catch (EJBException ex) {
          out.println(ex.getMessage());
     } catch (Exception ex) {
          out.println(ex.getMessage());
testlogin.jsp
<%
try{
     InitialContext ic = new InitialContext();
     MemberControllerHome home = (MemberControllerHome) ic.lookup("java:comp/env/ejb/MemberController");
     MemberController mc = home.create();
     out.println("You are logged in as <b>" + mc.getLoginID() +
          "</b> at level <b>" + mc.getLoginAccessLevel() + "</b>.");
} catch (NamingException ex) {
     out.println("java:comp/env/ejb/MemberController not found.");
} catch (EJBException ex) {
     out.println(ex.getMessage());
} catch (Exception ex) {
     out.println(ex.getMessage());
%>

The key to the problem is that in testlogin.jsp a new stateful session bean is created. The new bean instance of course doesn't know the log-in information you stored in the old session bean. That is why the method returns null and 0 when called.
There are couple of ways to solve the issue. The easiest solution is to store the bean instance created in Login.jsp in the jsp's implicit HttpSession object. Because login.jsp and testlogin.jsp share the same session, the bean instance can be easily stored and retrieved.
Here is the code you need to have:
1. in login.jsp
session.setAttribute("MemberControllerBeanInstance", mc);
2. in testlogin.jsp
MemberController mc =
(MemberController) session.getAttribute("MemberControllerBeanInstance");
Hope it helps.

Design question: When to use instance variables

Looking for best practice/design advise.
I am working my way through an exercise where I convert a zip code to a postal barcode (and back), validate the format, and validate/generate a check digit. My code works fine. I posted comments and methods below for reference. In addition to the book I am using, I also read http://java.sun.com/docs/books/tutorial/java/javaOO/classvars.html.
My question is: In designing this class, should I have defined instance variables to hold the generated zipcode, barcode, and checkdigit and then used getter methods to get the zipcode or barcode?
I planned on creating a user interface to ask for a zipcode or barcode and present a conversion to the user. The only methods that need to be called are "convertBarcodeToZipcode" and "convertZipcodeToBarcode". All the other methods are utility methods. The strings that are returned by these two methods are presented to the user.
I could, easily enough, create and populate instance variables, but would I keep the return statements as well or remove them?
Thanks, Mike
ps: I am self-learning java, so I don't have an instructor to ask. :)
public class PostalBarCode {
     * Constructor.
     * Set up the barcode ArrayList
    public PostalBarCode() {
            barcodeUnits.add("||:::");
            barcodeUnits.add(":::||");
            barcodeUnits.add("::|:|");
            barcodeUnits.add("::||:");
            barcodeUnits.add(":|::|");
            barcodeUnits.add(":|:|:");
            barcodeUnits.add(":||::");
            barcodeUnits.add("|:::|");
            barcodeUnits.add("|::|:");
            barcodeUnits.add("|:|::");
     * Convert a barcode to a zipcode.
     * Assumes the input format is valid. Validates the check digit
     * @param theBarcode string to be converted
     * @return the zipcode as a String of empty string for error
    public String convertBarcodeToZipcode(String theBarcode) {}
     * Convert the Zipcode to a barcode
     * @param theZipcode string to be converted
     * @return the barcode as a string
    public String convertZipcodeToBarcode(String theZipcode) {}
     * Determines if theString is a barcode
     * @param theString
     * @return true if the input is a barcode, false otherwise.
    public boolean isBarcode (String theString) {}
     * Determines of theString is a zip code
     * @param theString the string to test for 5 digits
     * @return true for a zip code, false otherwise
    public boolean isZipcode (String theString) {}
     * Convert a barcode to a zipcode.
     * Assumes the input format is valid. Validates the check digit
     * @param theBarcode string to be converted
     * @return the zipcode as a String of empty string for error
    public String convertBarcodeToZipcode(String theBarcode) {}
     * Convert the Zipcode to a barcode
     * @param theZipcode string to be converted
     * @return the barcode as a string
    public String convertZipcodeToBarcode(String theZipcode) {}
     * Calculate the check digit from the zipcode
     * @param theZipcode as a String
     * @return the the check digit or -1 for error
    public int calculateCheckDigitFromZipcode(String theZipcode) {}
     * Calculate the check digit from the barcode
     * @param theZipcode as a String
     * @return the the check digit or -1 for error
    public int calculateCheckDigitFromBarcode(String theBarcode) {}
     * Validate the format of the barcode.
     * Should be 6 blocks of 5 symbols each.
     * Also check if frame bars are present and strip them.
     * @param theBarcode
     * @return true for proper format, false for improper format
    public boolean validateBarcodeFormat (String theBarcode){}
    private ArrayList<String> barcodeUnits = new ArrayList<String>();
}

These are just my two cents. The various methods that determine whether something is a zip or bar code can easily remain static. After all, you probably don't want to create an instance and then call something like isValid(), although you could do so. The various other methods could easily be instance methods. You could have a toZipCode() or toBarCode() method in each object to convert from one to the other. I would personally throw something like ValidationException rather than returning -1 for your various check-digit methods.
- Saish

How to clone generic instance variables?

Hi guys,
If I have private class Item<T>
        private T value;
        private int priority;
        public Item(T value, int priority)
            this.value = value;
            this.priority = priority;
        @Override
        public Object clone()
            try
                Item copy = (Item)super.clone();
                copy.value = (T)value.clone();       //compiler errors, says: "clone has protected access in java.lang.Object"
                return copy;
            catch (CloneNotSupportedException e)
                return null;
    }So if the instance variable is of mutable type e.g. Person, how can I make sure that value.clone() is called on a Person object?

[http://www.angelikalanger.com/GenericsFAQ/FAQSections/ProgrammingIdioms.html#FAQ502|http://www.angelikalanger.com/GenericsFAQ/FAQSections/ProgrammingIdioms.html#FAQ502]

Servlet instance variables

This might be a dumb question, but I'll ask it anyway...
I have methods in my servlet to handle registration, specifically creating address, customer and order objects.
All the information needed for creating my objects is coming from the registration form.
Right now if I were to call the createAddress() method, I have to pass the request object.... createAddress(request);
Would it be "thread safe" to make an instance variable of the request and refer to it using getters/setters? Or would it be wiser (and best practice) to make instance variables for the request attributes (like firstName, lastName, etc.)? Or am I way off and shouldn't be doing any of the above?
Thanks for the help.

GB_java_guy wrote:
To answer you question, I think it's different, from what I've read, because request attributes are supposed to be thread safe and I'd be using the request attributes instead of the request object.You said something about "making instance variables for the request attributes." I don't know what you mean by that, but if it's instance variable in the servlet class, don't do it.
I have no clue what you mean by "request attirbutes intead of request object."
So are you saying I should just use the request object and pass that to my methods instead? In general, yes. In some cases you may want to pass individual pieces of it--e.g. if there's a method that doesn't need to know or care about the fact that you're operating in a servlet context, and just needs a couple values to do its job.

Array as Instance Variable

Friends,
Hope you can get me on the right track with this. I have an array (that must be an instance variable of type double) :
private double[] myArray;
that stores two values at each index:
double length
char unitOfMeasure
We have to develop a method which will perform a different calculation on the value based on the identity of the unitOfMeasure.
The method I'm working on looks like this:
public double getDistance (int index)
if (myArray[index].unitOfMeasure == 'a')
return ....
else .....
The problem is that I get an error that reads "double cannot be dereferenced" I guess this is b/c you can't make a call with a primitive.
How then, do I get the value of the unitOfMeasure at a particular index (as opposed to the value of length at that same index)?
thanks!

Thanks, I understand - much easier to do this way.Above all it's possible. You can never store more
than one value at an array index position. At least
not at the same time -:)private static int VALUE_INDEX = 0;
private static int UNIT_OF_MEASURE_INDEX = 1;
private double[][] doubles;
doubles = new double[42][2];

Calling instance variable...

Similar Messages

Maybe you are looking for