.Class Instance

How do I create an instance of a .class file (In my program I should not have the .java file) and running his methods?
thanks in advance

Ok guys..
It's a few days I'm getting mad about this..(is for
my thesis)..
Tomorrow I sent an email to my professor about this
problem and he had replied that "You don't have to
use .java source file , but instead You have to save
Your code (-I know how to..and I have the require and
right contents-) in a .class file,which You can
directly invoke".
..this is what he writes me...sigh...you did this tomorrow? that's awfully clever of you both. can you give me any tips for horse races this weekend?? :-)
saving your code in a .class file would be, um, compiling it. are you sure that's what he will have been going to mean? .java and .class files are simply ways of representing code on disk. in the java runtime, everything's Classes and Objects ( or primitives ) we don't think in terms of "running a file". it's a mismatch of concepts

Similar Messages

How to reference the class-instance, created in parent class.

Hi, I have following scenario. During compilation I am gettting error message -- "cannot resolve symbol - symbol : Variable myZ"
CODE :
under package A.1;
     ClassZ
     Servlet1
          ClassZ myZ = new ClassZ;
under package A.2;
     Servlet2 extends Servlet1
          myZ.printHi();
How to reference the class-instance created in the parent class?

some corrections ...
under package A.1;
     ClassZ
     Servlet1
          init()
               ClassZ myZ = new ClassZ;
under package A.2;
     Servlet2 extends Servlet1
          myZ.printHi();

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.

How to get a reference to the owner of a class instance?

Within a method of a class, how can I get a reference to the
object containing the class instance?
To be clear: I have class B that contains a method, say
"myfunc()". Class A (say, the application itself or a custom
component) instantiates a new instance of Class B : myclassB=new
ClassB()
Now, from within myfunc() can I get a reference to Class A?
The simplest way here is to pass a "this" reference when
calling myfunc(), i.e. "myclassB.myfunc(this)" but I would prefer
not to have to remember to always use 'this'.

Are these objects within each other. Does classA own classB?
If that is the case, then Greg is correct and it should be
available in parentDocument.
In projects in the past we have created a central
refObjectLocator object that is available to all objects.
Mostly we use events to communicate between objects. Dispatch
an event and let whoever listen for it.
Here is a copy of our reflocator if you are interested.
package com.goconfigure.model {
import mx.collections.ArrayCollection;
import com.adobe.cairngorm.model.ModelLocator;
import com.goconfigure.util.HashMap;
[Bindable]
public class RefObjectLocator implements ModelLocator {
// this instance stores a static reference to itself
private static var refObject : RefObjectLocator;
public var refObjectHM : HashMap = new HashMap();
// singleton: constructor only allows one model locator
public function AppLocator() : void {
if ( RefObjectLocator.refObject != null )
throw new Error( "Only one RefObjectLocator instance should
be instantiated" );
// singleton: always returns the one existing static
instance to itself
public static function getInstance() : RefObjectLocator {
if ( refObject == null )
refObject = new RefObjectLocator();
return refObject;
public function addRefObject( pRefObject : Object, pName :
String ) : void {
refObjectHM.put(pName,pRefObject);
public function getRefObject( pName : String ) : Object {
return refObjectHM.getValue(pName);
public function removeRefObject( pName : String ) : void {
refObjectHM.remove(pName);
public function clearRefObject() : void {
refObjectHM.clear();

Getting Class instance of a class

Dear Friends,
I need to get Class instance of a class in my project. Inorder to use the reflection API 's the package name of the class is needed , but it may not be available Only available thing is the name of the class file and the location where that file is existing .
Please suggest some method to get Class instance in this situation.
Shaiju.P

You can create a ClassLoader of your own. There's a simplified example in this thread (reply number 6):
http://forum.java.sun.com/thread.jsp?thread=538836&forum=31

Converting string into class instance

Hi all,
I want to convert a string which is a class instance in to that class object in the receiving class. I'm sending server's class object as string to another class which is a client.
Please any one suggest to solve this problem.
Thanks& regards,
Sai.

do you mean reflection?
http://java.sun.com/developer/technicalArticles/ALT/Reflection/
here is a simple example:
import java.lang.reflect.Field;
public class ThisClass{
public static void main(String[] args) {
try{
System.out.println("Variable Value: " + Variable);
String className = "ThisClass";
String varName = "Variable";
Class c = Class.forName("" + className);
Field f = c.getField("" + varName);
f.setInt(null, 123);
System.out.println("Variable Value: " + Variable);
} catch(Exception e){ System.out.println("Error: " + e); }
public static int Variable = 0;
}

Get class Instance, and then get hers attributes

Hi Gurus,
i'm new to ABAP Object,
creating an a BSP whit MVC controller i've try to implement the class controller,
but on a method of it i want to get instance of the class parents:
the class that i implement is an extension of CL_BSP_CONTROLLER2.
In this class in the method DO_REQUEST ( for example ) i try to get the instance of the class
parent ( and i got it! ) using this syntax:
data: Parent type ref to IF_BSP_DISPATCHER,   " type take from attribute M_PARENT of the class
Parent = ME->M_PARENT.
In debug i see that 'Parent' get rightly the class parent instance but than i want do this:
(i want get the sub controller of the main contoller 'parent', in debug i can see everything fine)
   SubController = Parent->GET_ATTRIBUTE(LEFT_CONTROLLER).
But the compiler say that the class instance 'Parent' has no methods and no attribute.
i've try other syntax like:
    call METHOD Parent_>GET_ATTRIBUTE
        IMPORTING
     LEFT_CONTROLLER)
call METHOD ME->M_PARENT->GET_CONTROLLER
   EXPORTING
     CONTROLLER_ID = 'search'
   IMPORTING
     CONTROLLER_INSTANCE = Parent2
No one work!
How can i do?
Here screnshot of that i see in debug mode, and that i want get:
http://img190.imageshack.us/i/1debugscreen.jpg/
http://img10.imageshack.us/i/2debugscreen.jpg/
Thanks in advance,
Davide

Hi Pawan,
classes ref to CL_BSP_CONTROLLER2 like my controller class, have an attribute
M_PARENT type IF_BSP_DISPATCHER.
If the class is a subclass of an main class it has the M_PARENT attribute containing the instance of the parent class,
i can see in debug mode ( here example: http://img40.imageshack.us/img40/1648/3debugscreen.jpg )
i can get this attribute:
data: Parent type ref to IF_BSP_DISPATCHER,   " type take from attribute M_PARENT of the class
Parent = ME->M_PARENT.
but the interface IF_BSP_DISPATCHER has no attribute and no method defined, and if i declare 'Parent' as type ref to
CL_BSP_CONTROLLER2 the compiler return error
      <=>      "The type of "PARENT" cannot be converted to the type of "ME->M_PARENT". "
Davide

Sending class instance to an external application

Hi,
I was wondering if it is possible to send an instance of a class that has been initialized and instantiated to an external application as a parameter to the application?
Thanks in advance.

I dont thin that is posible since the java doc says
Class Class is special cased within the Serialization Stream Protocol. A Class instance is written initially into an ObjectOutputStream in the following format:
TC_CLASS ClassDescriptor
A ClassDescriptor is a special cased serialization of
a java.io.ObjectStreamClass instance.
A new handle is generated for the initial time the class descriptor is written into the stream. Future references to the class descriptor are written as references to the initial class descriptor instance.
So am not sure whether you can create new instances from the deserialized classes.

Creating custom class instances for XML nodes

Hi guys,
I'm trying to load an external XML document in my application
and create an instance of a custom class for each node in the XML
based on the value of some of their elements. The instances created
will eventually end up in a DataGrid by the way. The problem I'm
having is there seems to be many ways of doing small parts of this
and I have no idea how to make them all gel. Initially I'm using
HTTPService to load the XML file but I've seen people just use an
XML object. Then, after that, I initially set the loaded XML to an
ArrayCollection but others have used XMLList or XMLListCollection.
I've no idea what's the best way to do this.
Eventually, when I've created all of these instances by
looping over the XML and creating them how will I make them
bindable to the data grid? I'm guessing I'll have to group them
somehow...
Any help would be greatly appreciated. Thanks

Hey Tracy,
That is exactly what I was talking about in a previous post
you replied to
http://www.adobe.com/cfusion/webforums/forum/messageview.cfm?catid=585&threadid=1344350
Anyhow, Below is some code I created to do what your saying
somewhat dynamically. The idea being you can have many different
object types that you may want to populate with data from XML. In
my case I am using e4x as the result type from my web services. At
present I have about 6 different classes that call this function.
I'd love to get some opinions on the function. Good bad or
???? Any improvements etc????
package . . . .
import flash.utils.describeType;
import flash.utils.getDefinitionByName;
import flash.utils.getQualifiedClassName;
import mx.utils.ObjectUtil;
* Utility class to convert xml based Objects to class
instances.
* Takes a value object as the destination and an xmlList of
data
* Look through all the items in the value object. Note we
are using classInfo..accessor since
* our objects are bound all variables become getter /
setter's or accessors.
* Also note, we can handle custom objects, arrays and
arrayCollections.
* History
* 03.11.2008 - Steven Rieger : Created class
public final class XMLToInstance
public static function xmlToInstance( destinationObject :
Object, sourceXMLList : XMLList ) : void
// Get the class definition in XML, from the passed in
object ( introspection so to speak )
var classInfo : XML = describeType( destinationObject );
// Loop through each variable defined in the class.
for each ( var aVar : XML in classInfo..accessor )
// If this is String, Number, etc. . . Just copy the data
into the destination object.
if( isSimple( aVar.@type ) )
destinationObject[aVar.@name] = sourceXMLList[aVar.@name];
else
// Dynamically create a class of the appropriate type
var className : String = aVar.@type;
var ObjectClass : Class = getDefinitionByName( className )
as Class;
var newDestObject : Object = Object( new ObjectClass());
// If this is a custom type
if( isCustomType( className ) && ObjectClass != null
// Recursively call itself passing in the custom data type
and the data to store in it.
// I haven't tested nested objects more than one level. I
suppose it should work.
// Note to self. Check.
xmlToInstance( newDestObject, sourceXMLList[aVar.@name] );
else
// Must be some sort of Array, Array Collection . . .
if( ObjectClass != null )
var anXMLList : XMLList = new XMLList(
sourceXMLList[aVar.@name] );
for each( var anItem : XML in anXMLList )
// I'm sure there are more types, just not using any of them
yet.
if( newDestObject is Array )
newDestObject.push( anItem )
else
newDestObject.addItem( anItem );
// Add the data to the destination object. . . .
destinationObject[aVar.@name] = newDestObject;
} // end function objectToInstance
public static function isSimple( dataType : String ) :
Boolean
* This function is pretty self explanatory.
* Check to see if this is a simple data type. Did I miss
any?
* History
* 03.11.2008 - Steven Rieger : Created function
switch( dataType.toLowerCase() )
case "number":
case "string":
case "boolean":
return true;
return false;
} // end isSimple
public static function isCustomType( className : String ) :
Boolean
* This function is pretty self explanatory.
* Check to see if this is a custom data type. Add them here
as you need. . .
* History
* 03.11.2008 - Steven Rieger : Created function
var aClassName : String = className.replace( "::", "."
).toLowerCase();
aClassName = aClassName.substr( aClassName.lastIndexOf( "."
) + 1, aClassName.length - aClassName.lastIndexOf( "." ) );
switch( aClassName )
case "ndatetimevo":
case "expenselineitemvo":
return true;
return false;
} // end isCustomType
} // end class
} // end package

Class Instance access

Is it possible to make an instance of a class available for
reading / writing to on all documents in an application? If so, how
is it done?
I have an application written that asks a user to login. When
the user enters their information (email / password), information
including their name, email address, date of last login, etc. is
pulled from my database and a class instance is populated on the
current page (lower level page). I would like to reference
different parts of this class instance on multiple documents. For
example, I would like to display a label that has a text property
of "Hello, Jack", where 'Jack' is a variable held in the class
instance on another page at the same level as the current
page.

You need to have a look at the Singleton Pattern. Here is a
link that might help you
http://flexrays.wordpress.com/2007/06/20/singleton-pattern/

Any way to for a class instance to ask what its instance name is?

Hey. I have a class which needs to create a movie clip on the
stage. Since each instance of the class will only ever have 1 movie
clip on the stage at a time, it seems reasonable that I have the
instance create a movie clip with its own name, prefixed with "mc_"
or something of the sort.
Here's where I don't know quite what to do... How do I get at
this information? For instance, when you a dealing with an XMLNode,
you can simply use...
the_answer = xmlNodeInstance.nodeName;
...I know the analogy fails, but hopefully you know what I'm
looking for.
Thanks!

hu....
and when you create your movie clip, (assuming you don't just
build it at authoring time) you specify an instance id through the
createEmptyMovieClip function....
taking a cue from this, I'm guessing that my answer is to
change the structure of what I'm doing a little... instantiate my
object with an instance name as a parameter given to the Class
Constructor... that way the class can have it's own name on file.
I guess my only concern there is how do I keep the "name"
variable from being just completely arbitrary...?
I guess I'm getting away from application (becaust I don't
know when I'd do this...) and into theory.... but for instance,
let's say I create my class like this:
var instanceReference:mySuperCoolClass = new
mySuperCoolClass("instanceName");
So. I have my class instance... ideally, the class would
exist on the stage as "instanceName", with "instanceReference"
being another way to reference the instance. That would be ideal...
but how do I make that happen? Because in the scenario of what I've
just done, I see the class instance existing on the stage as
"instanceReference", and I've just passed it a fun, but meaningless
bit of data called "instanceName"...
I suppose I could have the class go back to "_parent" and
create it's own object.... but here again I'm getting into
territory that feels a lot like i have no idea what I'm doing...
haha!
I guess I have enough info to get back to coding for now...
But I'm deffinately open to more tips... I feel like I'm still
missing how a lot of this works.
(I'm at that awkward place where I can easily explain what
OOP is, but I'm far from experienced in how to implement it... I've
only written about half a dozen classes so far... so I still have a
lot to learn. Thanks for your patience, all of you!)

Initialize/set a base class from a another base class instance

Hi,
How can I initialize/set a base class from a another base class instance? I do not want to do a copy of it.
It would look something like:
class A {...}
class B extends A
    B(A a)
        // super = a;
    setA(A a)
        // super = a;
}Thank you.

erikku wrote:
Thanks Winton. It is what I did first but A has lots of methods and if methods are later added to A, I will have to edit B again. For those two reasons, I wanted to use inheritance. The part I was not sure with was the way to initialize B's base (A).You pays your money and you takes your choice. One way (this way) you have to provide forwarders; the other way (inheritance) you have to provide constructors (and if A has a lot of em, you may be writing quite a few).
Ask yourself this question: is every B also an A? No exceptions. Ever.
If the answer is 'yes', then inheritance is probably the best way to go.
However, if there is even the remotest chance that an instance of B should not exhibit 100% of the behaviour of A, now or in the future, then the wrapper style is probably what you want.
Another great advantage of the wrapper style is that methods can be added to A without affecting the API for B (unless you want to).
Winston
PS: If your Class A has a constructor or constructors that take a pile of parameters, you might also want to look at the Builder pattern. However, that's not really what we're talking about here, and it should probably be implemented on A anyway.

Able to store abap class instance in trex

HEllo all,
I am new to enterprise search,is it possible to store an abap class instance in trex,basically i store a key value and
an abap class instance against this key value.
regards
kaushik

Good one, Singleton is definitely a good way of doing things.
But I'm looking for way to track instance of object, isn't it really no way of doing so?
Then why tools like jps (java version of ps (like command in unix) ) is possible?
Isn't there a generic way to do this, since Java was build from the ground up with object -oriented in mind, why these pool of objects are not maintainable by user(a developer in this case)?

Class Instances

Quick question regarding best practices for class instances.
Is is best to create one class instance and keep a reference to it and reuse that class as needed or should I let that instance be garbage collected and create a new instance as needed?
I have a class in a project that will format and output data to a file. Basically this is recording transactions inputted by the user. I would estimate that this would get called, at the most, 25 times per day.
So is it best to call a new instance or just create one and reuse it?
Thanks,
ton80

ton80 wrote:
Quick question regarding best practices for class instances.
Is is best to create one class instance and keep a reference to it and reuse that class as needed or should I let that instance be garbage collected and create a new instance as needed?Reusing or recycling the class (object pooling) may increase performance, but there's a cost associated. Code complexity increases, more code to maintain, etc. And it's doubtful you'll see performance gains. On the other hand, depending on the app, it may yield huge performance gains.
I have a class in a project that will format and output data to a file. Basically this is recording transactions inputted by the user. I would estimate that this would get called, at the most, 25 times per day.
So is it best to call a new instance or just create one and reuse it?Just create the instance inside of a method, each time you need it. At the end of the method, simply let the object fall out of scope. I don't see a case for reuse here whatsoever.

The difference between class, instances and object?

I've been reading a JAVA book and i've come accross terms such as class, instances and object. What I don't understand is why after creating a class, we have to create an object and then create instances? What's an object and instance anyway? I don't really understand the term. Can anyone pls help and explain it to me in an easier way to understand?
Thanks a lot.

A Class defines what attributes (properties) and methods a particular item will have.
Ex. You have a class person
public class Person
public void walk()
String name;
int age;
}An instance and Object are the same. When you create an instance of a class, you get an object of that class.
Person kevonline = new Person();You can then set kev's name, age, make him walk, etc... since these are defined in the class Person.
HTH,
Dewang

Convert to class instance into string/binary

Hello friends,
is there a utility to convert a class instance into string or binary.
regards
kaushik

Take a look at CL_ABAP_STRING_UTILITIES
Best!
Jim

.Class Instance

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