Class overhead

I have created a Class with 10 fields and 20 methods;
I then create a JTable (10 x 100) with each cell holding a copy of the Class created.
My question is : Does each of these Class holding individual 20 methods? or does JVM manages each copy of the created Class having a shared method pool?

For documentation, see
Virtual machine specification section 2.17.6
Creation of New Class Instances. Note that that talks about data - code is not
discussed.True, but if that can be assumed to completely
describe what memory is allocated when an instance is
created, then the absence of any mention of code
implies that no memory is allocated for code when an
instance is created.Just as one would assume that a reasonable implementation of a JVM would limit the duplication of the byte code. However a naive implementation could do that.
And the specs do not specifically state that code duplication does not occur. So the request above for docs is going to be limited to something, if it exists, that states that the Sun JVM does not duplicate code. I don't consider it likely that anyone bothered to document that simply because it is so obvious. But that means that there are no documents that state that.

Similar Messages

Class overhead, function overhead and parameter overhead

Hi all,
I am interested in class overhead, function overhead (each function in a class) and parameter overhead (each parameter in function).
I saw somewhere that class overhead are 200 bytes.
Is it wise to give up on class and go for functional programming? (Only classes required to run the j2me app are created and nothing else)
How does function get called? Does it work like a stack? Where each parameters get pushed into the stack and later on pop out when control pass on to the function?
If your program is full of functions doesn't this make it very processor intensive?
What is the best solution?
Thanks in advance!

Hallo,
silly question: but what exactly do you mean when you say "full of attributes and methods that will never be used for this instance"?
I assume that when you have created your class you thought about the attributes and methods you wanted to include, and have not included any unnecessary baggage. I can only think that, perhaps, you have a class X that you would like to reuse, because it does all that you want. The only problem is that, for your specific problem, it carries a lot of excess baggage with it. You only need a few of the attributes and methods. Am I correct?
Such a class reuse will certainly incur some overheads, but let us try to analyse where they are:
1. Extra Code. The 'big' class is already defined and probably already loaded, so there should not be any overheads for the code.
2. Extra Data. Certainly creating a new instance of the 'big' class will require more memory. The question is how big is 'big' class, and how many instances do you want to create or have in existance at any one time? If the class is less than a few kB big and you only need a few instances at any one time, then you can afford to ignore the overhead.
3. Performance. Every time that you create an instance of the 'big' class, the processor must do some work to initialize it. The question is, what is required to initialize the class? This depends on what is in the constructor.
4. Programmer Time. If there is an existing class, then it will (probably, depending on documentation) take less time to reuse the class
than to write another, streamlined class. Someone else will already (hopefully) have debugged the 'big' class.
I think my view would be to reuse 'big' class unless there good grounds not to do so (see above). Your time is more important than a few overheads.

Internal Order , object class related issue

hi
when i created internal order with the object class (Assignment Tab) :- Investment and not specified any assignment like (cost center ) i am able to view line items posted to internal order by transaction KOB1
but if i am selecting object class as Overhead and not specified any other assignment like (cost center )i am not able to see actual posted line items . so How we will get this line items ?
is there any other transaction available ?
Thanks in advance
sachin

HI,
I can view real actual postings for order object classes "Overhead costs, Investment, Production" using KOB1.
Check your postings (value type!) and your KOB1 selection screen.
Best regards, Christian

Wrong GR/IR account derivation for PM01 orders

Wrong GR/IR account derivation for PM01 orders which will settle to related WBS elements
Two gr/ir accounts have been determined with object class investment and overhead. The FI document picking up different accounts and not the same account for pm01/pm02/pm03/pm04 orders and the costs are getting settled to wrong wbs elements.(example a pm order with object class investment is getting settled to wbs element with object class overhead).The right account in not getting picked up.
Can anyone provide a suitable solution?
An early reply will be much appriciated
Thanks in advance
Shekhar
Edited by: V_Shekhar on May 12, 2011 6:16 PM

Dear Chandra,
Can you please share the screen shot of OB22 for your company code?
Regards,
Sachin

What do people think about the different Generic Java approaches?

I have seen a lot of different approaches for Generic Java, and when people find problems with each approach the normal response has been: the other approach is worse with such and such a problem, do you have a better way?
The different approaches I have seen are: (in no particular order)
Please correct me if I am wrong and add other approaches if they are worthy of mention.
1) PolyJ - by MIT
This is a completely different approach than the others, that introduces a new where clause for bounding the types, and involves changing java byte codes in order to meet it's goals.
Main comments were not a java way of doing things and far too greater risk making such big changes.
2) Pizza - by Odersky & Wadler
This aims at extending java in more ways than just adding Generics. The generic part of this was replaced by GJ, but with Pizza's ability to use primitives as generic types removed, and much bigger changes allowing GJ to interface with java.
Main comments were that Pizza doesn't work well with java, and many things in Pizza were done in parallel with java, hence were no longer applicable.
3) GJ - by Bracha, Odersky, Stoutamire & Wadler
This creates classes with erased types and bridging methods, and inserts casts when required when going back to normal java code.
Main comments are that type dependent operations such as new, instanceof, casting etc can't be done with parametric types, also it is not a very intuitive approach and it is difficult to work out what code should do.
4) Runtime Generic Information - by Natali & Viroli
Each instance holds information about its Runtime Type.
Main comments from people were that this consumes way too much memory as each instance holds extra information about its type, and the performance would be bad due to checking Type information at runtime that would have been known at compile.
5) NextGen - by Cartwright & Steele
For each parameterized class an abstract base class with types erased is made and then for each new type a lightweight wrapper class and interface are created re-using code from the base class to keep the code small.
Main comments from people were that this approach isn't as backwards compatible as GJ due to replacing the legacy classes with abstract base classes which can't be instantiated.
6) .NET common runtime - by Kennedy & Syme
This was written for adding Generics to C#, however the spec is also targeted at other languages such as VB.
Main comments from people were that this approach isn't java, hence it is not subject to the restrictions of changing the JVM like java is.
7) Fully Generated Generic Classes - by Agesen, Freund & Mitchell
For each new type a new class is generated by a custom class loader, with all the code duplicated for each different type.
Main comments from people were that the generated code size gets too big, and that it is lacking a base class for integration with legacy code.
8) JSR-14 - by Sun
This is meant to come up with a solution Generic Solution to be used in java. Currently it is heavily based on GJ and suffering from all the same problems as GJ, along with the fact that it is constantly undergoing change and so no one knows what to expect.
See this forum for comments about it.
As if we didn't have enough approaches already, here is yet another one that hopefully has all of the benefits, and none of the problems of the other approaches. It uses information learnt while experimenting with the other approaches. Now when people ask me if I think I have a better approach, I will have somewhere to point them to.
(I will be happy to answer questions concerning this approach).
9) Approach #x - by Phillips
At compile time 1 type is made per generic type with the same name.
e.g.class HashSet<TypeA> extends AbstractSet<TypeA> implements Cloneable, Serializable will be translated to a type: class HashSet extends AbstractSet implements Cloneable, SerializableAn instance of the class using Object as TypeA can now be created in 2 different ways.
e.g.Set a = new HashSet();
Set<Object> b = new HashSet<Object>();
//a.getClass().equals(b.getClass()) is trueThis means that legacy class files don't even need to be re-compiled in order to work with the new classes. This approach is completely backwards compatible.
Inside each type that was created from a generic type there is also some synthetic information.
Information about each of the bounding types is stored in a synthetic field.
Note that each bounding type may be bounded by a class and any number of interfaces, hence a ';' is used to separate bounding types. If there is no class Object is implied.
e.g.class MyClass<TypeA extends Button implements Comparable, Runnable; TypeB> will be translated to a type: class MyClass {
public static final Class[][] $GENERIC_DESCRIPTOR = {{Button.class, Comparable.class, Runnable.class}, {Object.class}};This information is used by a Custom Class Loader before generating a new class in order to ensure that the generic types are bounded correctly. It also gets used to establish if this class can be returned instead of a generated class (occurs when the generic types are the same as the bounding types, like for new HashSet<Object> above).
There is another synthetic field of type byte[] that stores bytes in order for the Custom Class Loader to generate the new Type.
There are also static methods corresponding to each method that contain the implementation for each method. These methods take parameters as required to gain access to fields, contructors, other methods, the calling object, the calling object class etc. Fields are passed to get and set values in the calling object. Constructors are passed to create new instances of the calling object. Other methods are passed when super methods are called from within the class. The calling object is almost always passed for non static methods, in order to do things with it. The class is passed when things like instanceof the generated type need to be done.
Also in this class are any non private methods that were there before, using the Base Bounded Types, in order that the class can be used exactly as it was before Generics.
Notes: the time consuming reflection stuff is only done once per class (not per instance) and stored in static fields. The other reflection stuff getting done is very quick in JDK1.4.1 (some earlier JDKs the same can not be said).
Also these static methods can call each other in many circumstances (for example when the method getting called is private, final or static).
As well as the ClassLoader and other classes required by it there is a Reflection class. This class is used to do things that are known to be safe (assuming the compiler generated the classes correctly) without throwing any exceptions.
Here is a cut down version of the Reflection class: public final class Reflection {
public static final Field getDeclaredField(Class aClass, String aName) {
 try {
 Field field = aClass.getDeclaredField(aName);
 field.setAccessible(true);
 return field;
 catch (Exception ex) {
 throw new Error(ex);
public static final Object get(Field aField, Object anObject) {
 try {
 return aField.get(anObject);
 catch (Exception ex) {
 throw new Error(ex);
public static final void set(Field aField, Object anObject, Object aValue) {
 try {
 aField.set(anObject, aValue);
 catch (Exception ex) {
 throw new Error(ex);
public static final int getInt(Field aField, Object anObject) {
 try {
 return aField.getInt(anObject);
 catch (Exception ex) {
 throw new Error(ex);
public static final void setInt(Field aField, Object anObject, int aValue) {
 try {
 aField.setInt(anObject, aValue);
 catch (Exception ex) {
 throw new Error(ex);
}Last but not least, at Runtime one very lightweight wrapper class per type is created as required by the custom class loader. Basically the class loader uses the Generic Bytes as the template replacing the erased types with the new types. This can be even faster than loading a normal class file from disk, and creating it.
Each of these classes has any non private methods that were there before, making calls to the generating class to perform their work. The reason they don't have any real code themselves is because that would lead to code bloat, however for very small methods they can keep their code inside their wrapper without effecting functionality.
My final example assumes the following class name mangling convention:
* A<component type> - Array
* b - byte
* c - char
* C<class name length><class name> - Class
* d - double
* f - float
* i - int
* l - long
* z - boolean
Final Example: (very cut down version of Vector)public class Vector<TypeA> extends AbstractList<TypeA> implements RandomAccess, Cloneable, Serializable {
protected Object[] elementData;
protected int elementCount;
protected int capacityIncrement;
public Vector<TypeA>(int anInitialCapacity, int aCapacityIncrement) {
 if (anInitialCapacity < 0) {
 throw new IllegalArgumentException("Illegal Capacity: " + anInitialCapacity);
 elementData = new Object[initialCapacity];
 capacityIncrement = capacityIncrement;
public synchronized void setElementAt(TypeA anObject, int anIndex) {
 if (anIndex >= elementCount) {
 throw new ArrayIndexOutOfBoundsException(anIndex + " >= " + elementCount);
 elementData[anIndex] = anObject;
}would get translated as:public class Vector extends AbstractList implements RandomAccess, Cloneable, Serializable {
public static final Class[][] $GENERIC_DESCRIPTOR = {{Object.class}};
public static final byte[] $GENERIC_BYTES = {/*Generic Bytes Go Here*/};
protected Object[] elementData;
protected int elementCount;
protected int capacityIncrement;
private static final Field $0 = Reflection.getDeclaredField(Vector.class, "elementData"),
 $1 = Reflection.getDeclaredField(Vector.class, "elementCount"),
 $2 = Reflection.getDeclaredField(Vector.class, "capacityIncrement");
static void $3(int _0, Field _1, Object _2, Field _3, int _4) {
 if (_0 < 0) {
 throw new IllegalArgumentException("Illegal Capacity: " + _0);
 Reflection.set(_1, _2, new Object[_0]);
 Reflection.setInt(_3, _2, _4);
static void $4(int _0, Field _1, Object _2, Field _3, Object _4) {
 if (_0 >= Reflection.getInt(_1, _2)) {
 throw new ArrayIndexOutOfBoundsException(_0 + " >= " + Reflection.getInt(_1, _2));
 ((Object[])Reflection.get(_3, _2))[_0] = _4;
public Vector(int anInitialCapacity, int aCapacityIncrement) {
 $3(anInitialCapacity, $0, this, $2, aCapacityIncrement);
public synchronized void setElementAt(Object anObject, int anIndex) {
 $4(anIndex, $1, this, $0, anObject);
} and new Vector<String> would get generated as:public class Vector$$C16java_lang_String extends AbstractList$$C16java_lang_String implements RandomAccess, Cloneable, Serializable {
protected Object[] elementData;
protected int elementCount;
protected int capacityIncrement;
private static final Field $0 = Reflection.getDeclaredField(Vector$$C16java_lang_String.class, "elementData"),
 $1 = Reflection.getDeclaredField(Vector$$C16java_lang_String.class, "elementCount"),
 $2 = Reflection.getDeclaredField(Vector$$C16java_lang_String.class, "capacityIncrement");
public Vector$$C16java_lang_String(int anInitialCapacity, int aCapacityIncrement) {
 Vector.$3(anInitialCapacity, $0, this, $2, aCapacityIncrement);
public synchronized void setElementAt(String anObject, int anIndex) {
 Vector.$4(anIndex, $1, this, $0, anObject);
}Comparisons with other approaches:
Compared with PolyJ this is a very java way of doing things, and further more it requires no changes to the JVM or the byte codes.
Compared with Pizza this works very well with java and has been designed using the latest java technologies.
Compared with GJ all type dependent operations can be done, and it is very intuitive, code does exactly the same thing it would have done if it was written by hand.
Compared with Runtime Generic Information no extra information is stored in each instance and hence no extra runtime checks need to get done.
Compared with NextGen this approach is completely backwards compatible. NextGen looks like it was trying to achieve the same goals, but aside from non backwards compatibility also suffered from the fact that Vector<String> didn't extend AbstractList<String> causing other minor problems. Also this approach doesn't create 2 types per new types like NextGen does (although this wasn't a big deal anyway). All that said NextGen was in my opinion a much better approach than GJ and most of the others.
Compared to .NET common runtime this is java and doesn't require changes to the JVM.
Compared to Fully Generated Generic Classes the classes generated by this approach are very lightweight wrappers, not full blown classes and also it does have a base class making integration with legacy code simple. It should be noted that the functionality of the Fully Generated Generic Classes is the same as this approach, that can't be said for the other approaches.
Compared with JSR-14, this approach doesn't suffer from GJ's problems, also it should be clear what to expect from this approach. Hopefully JSR-14 can be changed before it is too late.

(a) How you intend generic methods to be translated.
Given that Vector and Vector<Object> are unrelated types,
what would that type be represented as in the byte code of
the method? In my approach Vector and Vector<Object> are related types. In fact the byte code signature of the existing method is exactly the same as it was in the legacy code using Vector.
To re-emphasize what I had said when explaining my approach:
System.out.println(Vector.class == Vector<Object>.class); // displays true
System.out.println(Vector.class == Vector<String>.class); // displays false
Vector vector1 = new Vector<Object>(); // legal
Vector<Object> vector2 = new Vector(); // legal
// Vector vector3 = new Vector<String>(); // illegal
// Vector<String> vector4 = new Vector(); // illegal
Vector<String> vector5 = new Vector<String>(); // legal
You must also handle the case where the type
parameter is itself a parameterized type in which the type
parameter is not statically bound to a ground instantiation.This is also very straightforward: (let me know if I have misunderstood you)
(translation of Vector given in my initial description)
public class SampleClass<TypeA> {
public static void main(String[] args) {
 System.out.println(new Vector<Vector<TypeA>>(10, 10));
}would get translated as:public class SampleClass {
public static final Class[][] $GENERIC_DESCRIPTOR = {{Object.class}};
public static final byte[] $GENERIC_BYTES = {/*Generic Bytes Go Here*/};
private static final Constructor $0 = Reflection.getDeclaredConstructor(Vector$$C16java_util_Vector.class, new Class[] {int.class, int.class});
static void $1(Constructor _0, int _1, int _2) {
 try {
 System.out.println(Reflection.newInstance(_0, new Object[] {new Integer(_1), new Integer(_2)}));
 catch (Exception ex) {
 throw (RuntimeException)ex;
public static void main(String[] args) {
 $1($0, 10, 10);
}and SampleClass<String> would get generated as:public class SampleClass$$C16java_lang_String {
private static final Constructor $0 = Reflection.getConstructor(Vector$$C37java_util_Vector$$C16java_lang_String.class, new Class[] {int.class, int.class});
public static void main(String[] args) {
 SampleClass.$1($0, 10, 10);
Also describe the implementation strategy for when these
methods are public or protected (i.e. virtual).As I said in my initial description that for non final, non static, non private method invocations a Method may be passed into the implementing synthetic method as a parameter.
Note: the following main method will display 'in B'.
class A {
public void foo() {
 System.out.println("in A");
class B extends A {
public void foo() {
 System.out.println("in B");
public class QuickTest {
public static void main(String[] args) {
 try {
 A.class.getMethod("foo", null).invoke(new B(), null);
 catch (Exception ex) {}
}This is very important as foo() may be overwritten by a subclass as it is here. By passing a Method to the synthetic implementation this guarantees that covariance, invariance and contra variance all work exactly the same way as in java. This is a fundamental problem with many other approaches.
(b) The runtime overhead associated with your translationAs we don't have a working solution to compare this to, performance comments are hard to state, but I hope this helps anyway.
The Class Load time is affected in 4 ways. i) All the Generic Bytes exist in the Base Class, hence they don't need to be read from storage. ii) The custom class loader, time to parse the name and failed finds before it finally gets to define the class. iii) The generation of the generic bytes to parametric bytes (basically involves changing bytes from the Constant Pool worked out from a new Parametric type, Utf8, Class and the new Parametric Constant types may all be effected) iv) time to do the static Reflection stuff (this is the main source of the overhead). Basically this 1 time per class overhead is nothing to be concerned with, and Sun could always optimize this part further.
The normal Runtime overhead (once Classes have been loaded) is affected mainly by reflection: On older JDKs the reflection was a lot slower, and so might have made a noticeable impact. On newer JDKs (since 1.4 I think), the reflection performance has been significantly improved. All the time consuming reflection is done once per class (stored in static fields). The normal reflection is very quick (almost identical to what is getting done without reflection). As the wrappers simply include a single method call to another method, these can be in-lined and hence made irrelevant. Furthermore it is not too difficult to make a parameter that would include small methods in the wrapper classes, as this does not affect functionality in the slightest, however in my testing I have found this to be unnecessary.
(c) The space overhead (per instantiation)There are very small wrapper classes (one per new Type) that simply contain all non private methods, with single method calls to the implementing synthetic method. They also include any fields that were in the original class along with other synthetic fields used to store reflected information, so that the slow reflection only gets done once per new Type.
(d) The per-instance space overheadNone.
(e) Evidence that the proposed translation is sound and well-defined for all relevant cases (see below)Hope this is enough, if not let me know what extra proof you need.
(f) Evidence for backward compatibility
(For example, how does an old class file that passes a Vector
to some method handle the case when the method receives a Vector<T>
where T is a type parameter? In your translation these types are unrelated.)As explained above, in my approach these are only unrelated for T != Object, in the legacy case T == Object, hence legacy code passing in Vector is exactly the same as passing in Vector<Object>.
(g) Evidence for forward compatibility
(How, exactly, do class files that are compiled with a generics compiler run on an old VM)They run exactly the same way, the byte codes from this approach are all legal java, and all legal java is also legal in this approach. In order to take advantage of the Generics the Custom Class Loader would need to be used or else one would get ClassNotFoundExceptons, the same way they would if they tried using Collections on an old VM without the Collections there. The Custom Class Loader even works on older VMs (note it may run somewhat slower on older VMs).
(h) A viable implementation strategyType specific instantiations are at Class Load time, when the Custom Class Loader gets asked for a new Class, it then generates it.
The type specific instantiations are never shipped as they never get persisted. If you really wanted to save them all you need to do is save them with the same name (with the $$ and _'s etc), then the class loader would find them instead of generating them. There is little to be gained by doing this and the only reason I can think of for doing such a thing would be if there was some reason why the target VM couldn't use the Custom Class Loader (the Reflection class would still need to be sent as well, but that is nothing special). Basically they are always generated at Runtime unless a Class with the same name already exists in which case it would be used.
The $GENERIC_DESCRIPTOR and $GENERIC_BYTES from the base class along with the new Type name are all that is required to generate the classes at runtime. However many other approaches can achieve the same thing for the generation, and approaches such as NextGen's template approach may be better. As this generation is only done once per class I didn't put much research into this area. The way it currently works is that the $GENERIC_DESCRIPTOR are basically used to verify that a malicious class files is not trying to create a non Type Safe Type, ie new Sample<Object>() when the class definition said class Sample<TypeA extends Button>. The $GENERIC_BYTES basically correspond to the normal bytes of a wrapper class file, except that in the constant pool it has some constants of a new Parametric Constant type that get replaced at class load time. These parametric constants (along with possibly Utf8 and Class constants) are replaced by the Classes at the end of the new type name, a little more complex than that but you probably get the general idea.
These fine implementation details don't affect the approach so much anyway, as they basically come down to class load time performance. Much of the information in the $GENERIC_BYTES could have been worked out by reflection on the base type, however at least for now simply storing the bytes is a lot easier.
Note: I have made a small syntax change to the requested class:
public T(X datum) --> public T<X>(X datum)
class T<X> {
private X datum;
public T<X>(X datum) {
 this.datum = datum;
public T<T<X>> box() {
 return new T<T<X>>(this);
public String toString() {
 return datum.toString();
public static void main(String[] args) {
 T<String> t = new T<String>("boo!");
 System.out.println(t.box().box());
}would get translated as:
class T {
public static final Class[][] $GENERIC_DESCRIPTOR = {{Object.class}};
public static final byte[] $GENERIC_BYTES = {/*Generic Bytes Go Here*/};
private Object datum;
private static final Field $0 = Reflection.getDeclaredField(T.class, "datum");
private static final Constructor $1 = Reflection.getDeclaredConstructor(T$$C1T.class, new Class[] {T.class});
static void $2(Field _0, Object _1, Object _2) {
 Reflection.set(_0, _1, _2);
static Object $3(Constructor _0, Object _1) {
 try {
 return Reflection.newInstance(_0, new Object[] {_1});
 catch (Exception ex) {
 throw (RuntimeException)ex;
static String $4(Field _0, Object _1) {
 return Reflection.get(_0, _1).toString();
static void $5() {
 T$$C16java_lang_String t = new T$$C16java_lang_String("boo!");
 System.out.println(t.box().box());
public T(Object datum) {
 $2($0, this, datum);
public T$$C1T box() {
 return (T$$C1T)$3($1, this);
public String toString() {
 return $4($0, this);
public static void main(String[] args) {
 $5();
}as the generic bytes aren't very meaningful and by no means a requirement to this approach (NextGen's template method for generation may work just as well), here are the generated classes with some unused code commented out instead:
class T$$C28T$$C22T$$C16java_lang_String {
private T$$C22T$$C16java_lang_String datum;
private static final Field $0 = Reflection.getDeclaredField(T$$C28T$$C22T$$C16java_lang_String.class, "datum");
// private static final Constructor $1 = Reflection.getDeclaredConstructor(T$$C34T$$C28T$$C22T$$C16java_lang_String.class, new Class[] {T$$C28T$$C22T$$C16java_lang_String.class});
public T$$C28T$$C22T$$C16java_lang_String(T$$C22T$$C16java_lang_String datum) {
 T.$2($0, this, datum);
// public T$$C34T$$C28T$$C22T$$C16java_lang_String box() {
// return (T$$C34T$$C28T$$C22T$$C16java_lang_String)T.$3($1, this);
public String toString() {
 return T.$4($0, this);
public static void main(String[] args) {
 T.$5();
class T$$C22T$$C16java_lang_String {
private T$$C16java_lang_String datum;
private static final Field $0 = Reflection.getDeclaredField(T$$C22T$$C16java_lang_String.class, "datum");
private static final Constructor $1 = Reflection.getDeclaredConstructor(T$$C28T$$C22T$$C16java_lang_String.class, new Class[] {T$$C22T$$C16java_lang_String.class});
public T$$C22T$$C16java_lang_String(T$$C16java_lang_String datum) {
 T.$2($0, this, datum);
public T$$C28T$$C22T$$C16java_lang_String box() {
 return (T$$C28T$$C22T$$C16java_lang_String)T.$3($1, this);
public String toString() {
 return T.$4($0, this);
public static void main(String[] args) {
 T.$5();
class T$$C1T {
private T datum;
private static final Field $0 = Reflection.getDeclaredField(T$$C1T.class, "datum");
// private static final Constructor $1 = Reflection.getDeclaredConstructor(T$$C6T$$C1T.class, new Class[] {T$$C1T.class});
public T$$C1T(T datum) {
 T.$2($0, this, datum);
// public T$$C6T$$C1T box() {
// return (T$$C6T$$C1T)T.$3($1, this);
public String toString() {
 return T.$4($0, this);
public static void main(String[] args) {
 T.$5();
class T$$C16java_lang_String {
private String datum;
private static final Field $0 = Reflection.getDeclaredField(T$$C16java_lang_String.class, "datum");
private static final Constructor $1 = Reflection.getDeclaredConstructor(T$$C22T$$C16java_lang_String.class, new Class[] {T$$C16java_lang_String.class});
public T$$C16java_lang_String(String datum) {
 T.$2($0, this, datum);
public T$$C22T$$C16java_lang_String box() {
 return (T$$C22T$$C16java_lang_String)T.$3($1, this);
public String toString() {
 return T.$4($0, this);
public static void main(String[] args) {
 T.$5();
}the methods from the Reflection class used in these answers not given in my initial description are:
public static final Object newInstance(Constructor aConstructor, Object[] anArgsArray) throws Exception {
 try {
 return aConstructor.newInstance(anArgsArray);
 catch (InvocationTargetException ex) {
 Throwable cause = ex.getCause();
 if (ex instanceof Exception) {
 throw (Exception)ex;
 throw new Error(ex.getCause());
 catch (Exception ex) {
 throw new Error(ex);
public static final Constructor getDeclaredConstructor(Class aClass, Class[] aParameterTypesArray) {
 try {
 Constructor constructor = aClass.getDeclaredConstructor(aParameterTypesArray);
 constructor.setAccessible(true);
 return constructor;
 catch (Exception ex) {
 throw new Error(ex);
}

How to estimate on-card application's total size

there is a similar topic before,
seems many experts count the size by self,
but i still have no idea about it.
can anyone guide me a direction to estimate this from CAP file?
for example, how do i know "new" an object's overhead?
i had read an article, which says "Class overhead is over 200 bytes",
can i count this from CAP file?
Thanks a lot.

I've never factored in the overhead because I believe that's left up to the vendors. Overhead might be covered somewhere in the JCVM spec.

Availability control not activated - Real Internal Orders

Hi Experts,
I have created one order type with Object class overhead, budget profile 0000001. Defined Tolerance Limits for Availability Control. And I have created one order and maintained budget. If postings are exceeding the budget, system is simply saving it not giving any alerts. I have done KO30, system showing the message "Availability control not activated in any further objects". Where I am missing the configurations?
Regards,
Rajeswari

Hi,
Check whether the commitment management has been activated.
Check in transaction OKKP for Order management & commitment mangement active in controlling area level.Check the company code assignment also in controlling area.
Then check the activation of the Activate Open-Item Management in Order Types in Tcode KOAO.
whether commitment mangement tick is active against the order type.
Activate the availability control as automatic orelse activate when you assign budget in KO22 transaction.
Check both the setting.In some case it may not work in DEV server if you active later,Transport request to QAS & check it will work.
Regards,
Raj

Mail to the User - Budget Exceeded

Hi,
I have done necessary settings for Internal Order Budgets & availability control. While doing PO with account assginment category A (Internal order also assigned), system giving message Budget Exceeded. Up to this everything is OK for me. I have maintained Budget Manager also for my order type, Object class Overhead cost etc., But still system is not sending any message to the particular user which I have assigned the user name(other username) in my budget manager. It is showing error message only at my user id. "Any help from the forum is appreciated.
Regards,
rajeswari

Budget request (Scenario SR61)
The form is sent to a processor who makes the budget change.
The processor executes the budget transaction in the SAP system.
Budget request requiring approval (Scenario SR62)
The form is sent to someone for approval. This person must approve the request.
The system forwards the request via workflow to the processor (determined by the role). This person changes the budget in the SAP system.
The approving manager can also execute the budget transaction.
The above are texts from the same path you mentioned:
I understood that
You need to have a workflow for SR62
In addition, this going to intranet, meaning that you should have your SCOT configured by basis administrators and your gateway must have been opened.
Then only these scenarios are going to work.
Regards,
Ravi

Possible Random Shutdowns

Greetings to All,
I have been reading all these posts regarding random shutdowns on the MacBooks, and although I have never had it happen on either of my MacBooks (Week 27 and 29), I have had to troubleshoot a few that were having some issues, at our campus, with what was thought to be random shutdowns. These are Faculty/Staff machines.
Since time was at a premium, for me, I only spot-checked the batch of 7 and took peoples word for it. They have been following the discussions, after someone enlightened them to the discussion pages. I had one shut down on me after about 15 minutes of run time and it had hung up on a printer issue. I tried it again after letting it cool down, and it did the same thing after 30 minutes this time, and it was only when I went to do a test print – it hung again. There could have been others with this problem, but I didn’t have time to play around, and the others that I did test were a matter of fixing the user more than anything else.
I wiped them all clean, and reinstalled the OS X 10.4.7 from scratch, as well as Office 2004, and all of the Adobe software. The machine in question was used here for almost a week putting it through its paces without a single issue. I gave it and the others back to the users and everything was fine until a couple of days ago – she had had it for a week, and the shutdown trouble started again.
It turns out that some unauthorized software was installed; some printer drivers were installed for use at home, and some strange off the wall open source games. I blew it all away, again, and reinstalled as I did before and it’s working OK again. I did the same thing on another one that came back with more unauthorized stuff installed and other changes. It’s clean and working as normal, and all the other units are reporting OK, as I check on the folks every day.
I did do one other thing, I reseated the memory chips in all of them - and we bought the additional memory from Apple. They all have 1.256 Gig of Ram.
These were all bought in late July, but I didn’t look at the week they were built.
I do not work for Apple, I’m the Network Manager/Engineer for a large community college, and one of the few Mac users that have a fairly high level of hardware experience with regards to the Macs, as well as PeeCees, Solaris, HP-UX and so on and so forth.
It appears that bad software; drivers, programs, etc can kill the machine as well as hardware. My personal MacBooks have been working fine, so far and they have been hard at work every day for many hours a day with Parallels loaded so I can manage my Microsoft Active Directory – works great, too. I also have PeeCee notebooks and am perfectly happy with them, but I prefer a Mac and I don't want to lug around more than one notebook at a time. My other MacBook stays home for use there.
Cheers……. ☺
iBook 12" 1.42 MacBook Black 2.0 Mac OS X (10.4.7) 17" iMac PPC, 17" iMac Intel, Powerbook 12" 867, G-4 Tower, iMac Flat Panel, mor

I agree that it may be to soon to tell if the issue has gone away, and I hope it has. At the current time all of those MacBooks are up and running - I just called two of users that had the most trouble and they are happy campers, as they use them everyday for their classes, overhead projectors, Key Note presentations, email, and all the usual stuff.
On another note, and your timing is perfect, the Macbook that has been giving us the most trouble is back, with the same unauthorized software back on it. It was doing the random shut down thing until I removed all that software. As soon as I did that and turned it on, it started working again, and as of this point in time I'm writing this on it. I have been using the thing all morning for my daily routines without a glitch. I even installed Parallels on it and will install Win XP later.
I don't think heat is the issue, because when it's not behaving correctly, it shutdown within a minute or two. I have felt underneath and it is at room temperature. It is a lot warmer when I have it working, like right now writing this and burning a CD.
Am I satisfied that it's fixed for good - not a chance, I need to test further and pass this notebook around to my staff for a week. The Faculty member won't take it back as she is not happy, has no confidence in it and has decided that she wanted her desktop back.
What I have may not be the same thing as the other postings have eluded to, or maybe it is - who knows. I have 40 of these things, with 30 of them in a lab situation, and so far so good - not a glitch. We have Freeze-X on them so they can't install anything on them in the labs, so each time they reboot, they revert back to the way they were configured - works cool. I can't do that to the Faculty/Staff, much to my chagrin.
All of these machines are from the same time frame - bought at the same time, in otherwords.
I'll keep watching the saga unfold, and post if anything for sure comes along in the way of a fix, that I may get directly from Apple. They don't seem to know much about this issue, right now.
Cheers ...............

PL/SQL to Java Interface - Overwhelming Overhead?

My company is running Oracle 10g R2. I am currently exploring the use of java classes from PL/SQL. This is because we have multiple code bases, including Java, PowerBuilder (which can interface with Java), and PL/SQL (which can interface with Java).
Doing some performance testing, I found some rather alarming results. Running a simple java function 1 million times, I tested performance of PL./SQL to java and PowerBuilder to Java.
In PL/SQL, the 1 mil calls executed in ~120 s.
In PowerBuilder, the 1 mil calls executed in ~54 s.
Is it possible that our database is incorrectly configured for best java performance? Not only does it appear that PowerBuilder, a much less pervasive language than PL/SQL, is over twice as fast, but the PB test was run on my laptop, which is no where near as powerful as the database server that the PL/SQL procedure ran against, leading me to believe that the performance gap is actually much wider.
Anyone have any tips to improve the performance? Or is this simply the nature of the beast? I can't seem to find any posts on the net about people experiencing huge PL/SQL to Java overhead, so I'm hoping it is just something I am doing wrong.
Thanks for your help!
-Brett Birschbach

Below is my test code. Any suggestions are appreciated.
Thanks!
-Brett
==================================================
Java Class:
public class TestConvert {
 // For running straight from Java
 public static void main(String[] args){
 System.out.println(callAndTime());
 // For running 1 mil calls with only one call from PowerBuilder or PL/SQL
 public static long callAndTime(){
 TestConvert.convertEsnDecToHex("13005454488");
 long start = System.currentTimeMillis();
 for (int i = 0; i < 1000000; i++){
 TestConvert.convertEsnDecToHex("13005454488");
 long end = System.currentTimeMillis();
 return end-start;
 // For performing the actual work
 public static String convertEsnDecToHex(String esn) {
 String result = null;
 result = Integer.toHexString(new Integer(esn.substring(0, 3)).intValue());
 result += Integer.toHexString(new Integer(esn.substring(3)).intValue());
 return result.toUpperCase();
 // Non-static wrapper necessary for PowerBuilder
 public String callAndTimeNS(){
 return String.valueOf(callAndTime());
 // Non-static wrapper necessary for PowerBuilder
 public String convertEsnDecToHexNS(String esn){
 return convertEsnDecToHex(esn);
}PL/SQL Script for 1 Million Java Calls:
DECLARE
var VARCHAR2( 20 );
t_begin NUMBER;
t_end NUMBER;
BEGIN
var := testconvert.convertesndectohex( '13005454488' );
t_begin := DBMS_UTILITY.get_time;
FOR i IN 1 .. 1000000
LOOP
 var := testconvert.convertesndectohex( '13005454488' );
END LOOP;
t_end := DBMS_UTILITY.get_time;
DBMS_OUTPUT.put_line( var );
DBMS_OUTPUT.put_line( ( t_end - t_begin ) / 100 || ' seconds' );
END;
/PowerBuilder for 1 Million Java Calls:
EJBConnection lEJBConn
TestConvert lnv_test
String ls_ret
Long i
Time t_begin, t_end
lEJBConn = CREATE EJBConnection
lEJBConn.CreateJavaInstance( lnv_test, "TestConvert")
ls_ret = lnv_test.convertesndectohexns("13005454488")
t_begin = now()
FOR i = 1 TO 1000000
 ls_ret = lnv_test.convertesndectohexns("13005454488")
NEXT
t_end = now()
MessageBox("Hex Version",ls_ret + " - " + String(SecondsAfter(t_begin, t_end)) + " seconds")
DESTROY lEJBConn

Please help me understand making and loading variable classes

Hi guys ,
I know that I am stupid but I just can't get this! AS3 says you need to load variables into a class? Please please give me a simple example
my variables look like this... (the whole point of playing around with variables was that if I had to make a change I could access one place and change them...
but now I realse that I can't access or call them outside the movie clip they are in:(
please hlep me!
var ans1="";
var ans2="";
var w1="ABN";
var def1="An ABN (Australian Business Number), is a personal number for your business that makes it easier and quicker to deal with government and other businesses.";
var w2="ACN";
var def2="An ACN is an Australian Company Number, which is a special number that each company gets to identify it. No two companies can have the same ACN";
var w3="Action Plan";
var def3="A business Action Plan will show What needs to be done and When it needs to be done by."
var w4="Advertising";
var def4="Advertising is producing information to let people know about your business and try to increase sales."
var w5="Promotions";
var def5="Promotions are where your business tries to increase the sales of a particular item through offering a good deal, advertising or a special display.";
var w6="Benefit";
var def6="A benefit is something good that you get. One benefit of doing exercise is getting fit, another benefit is losing weight.";
var w7="Business Mentor";
var def7="A business mentor is a trusted guide. Someone who has experience and has been successful in business and can help and advise you.";
var w8="Business Name";
var def8="A Business name is the name a business uses to do its work. It lets customers know who you are.";
var w9="Business Registration";
var def9="When you start a business you need to register your ABN, you may need to register your business name.";
var w10="Cash flow";
var def10="Cash Flow for a business is having enough cash saved to be able to pay your bills when they are due.";
var w11="Characteristic";
var def11="The characteristics of something are describing words about that thing.";
var w12="Charges";
var def12="A charge is something you have to pay, an expense.";
var w13="Company";
var def13="Is the same as a corporation. A company is a type of business that needs to be registered (either State or Federal) and has special legal status. A company can put Pty. Ltd after it’s business name.";
var w14="Competitor";
var def14="A competitor is another business that is challenging you for customers.";
var w15="Constitution";
var def15="A constitution in business is a list of rules and principles that a company has agreed to follow.";
var w16="Corporations Aboriginal and Torres Strait Islander Act";
var def16="In the 1960s and 1970s, various reviews advised the Australian Government of the need for legislation to make it easier for Indigenous communities and organisations to form corporations. As a result, the ACA Act was passed, allowing Aboriginal and Torres Strait Islander groups to form corporations for any social or economic purpose.";
var w17="Corporations Act";
var def17="The Australian Securities and Investments Commission (ASIC) have laws that apply to corporations and these are found in the Corporations Act.";
var w18="Cultural knowledge";
var def18="Cultural knowledge is special information that is held by a particular cultural group, this could include technologies (e.g. special ways of using materials, making and using tools), stories, language and song, cultural rules, taboos, regulations and oral history.";
var w19="Customer";
var def19="The customer is someone who is buying something from a business.";
var w20="Debt";
var def20="Is something that you have to pay back. If you borrow 20 dollars you have a $20 debt.";
var w21="Direct competitor";
var def21="Is selling exactly the same thing as your business and competing for your customers.";
var w22="Dividend";
var def22="A dividend is money that is paid to shareholders regularly out of the company’s profits.";
var w23="(Microsoft) Excel";
var def23="Microsoft Excel is a computer program that lets you keep lists of numbers and also add up totals and do other sums to those numbers.";
var w24="Fees";
var def24="A fee is something that you have to pay, an expense.";
var w25="Financial Management";
var def25="Financial Management is the planning, organising, checking and controlling of the income, expenses and Tax for a business.";
var w26="Franchise";
var def26="A franchise is a type of business you can buy. When you buy a franchise you set up the same type of business that has been successful somewhere else.";
var w27="General ledger";
var def27="A general ledger for a business is where all of the income and expenses for that business are kept in a document.";
var w28="Goal";
var def28="A goal is a target that you set yourself or your business. Something that you want to achieve.";
var w29="Growth opportunity";
var def29="A growth opportunity is a chance for a business to get bigger.";
var w30="GST";
var def30="The Goods and Services Tax is paid when you buy things. Some items like food and medicine do not have the Goods and Services tax charged to them.";
var w31="ICN";
var def31="Indigenous Corporations Number is a special number given each indigenous corporation to identify it. No two indigenous corporations can have the same ICN.";
var w32="Incorporate";
var def32="Incorporate is what people do when they create a company or corporation.";
var w33="Indirect competitor";
var def33="An indirect competitor is selling a similar product or service to your business. E.g. If you had a pizza shop, a fried chicken shop is an indirect competitor because it sells food and your customers might want to eat chicken instead of pizza.";
var w34="Labour";
var def34="Labour is all the work done by people (including you) in your business.";
var w35="Legal name";
var def35="Your Legal Name is the name that is on your Birth Certificate.";
var w36="Legal protection";
var def36="Legal protection means you are protected under the law from certain things happening.";
var w37="Legal structure (business)";
var def37="Legal structure is the type of business, sole trader, company, partnership.";
var w38="Liability";
var def38="A liability is something you are responsible for.";
var w39="Licence";
var def39="A license is proof that you have permission to do something. For example, if you have a driving license you can drive a car.";
var w40="Lodge";
var def40="To lodge a form means to send it to where it has to go.";
var w41="Manufacturing";
var def41="A manufacturing business makes things.";
var w42="Marketing budget";
var def42="A marketing budget is the amount of money you have set aside for advertising and promotion for your business.";
var w43="Minor criminal convictions";
var def43="A minor criminal conviction is something small you have been in trouble over with the police. Shop lifting is an example of a minor criminal conviction. ";
var w44="MYOB";
var def44="MYOB is financial management software for business.";
var w45="Networks";
var def45="A network for business is all of your contacts, customers and the people you know through doing business. ";
var w46="Obligations";
var def46="Obligations are things you are responsible for.";
var w47="One off";
var def47="A “one off” cost is something that only needs to be paid for once.";
var w48="Operating budget";
var def48="The Operating Budget is a record of the income and expenses of a business.";
var w49="Overheads";
var def49="Overheads are the expenses or costs in running your business, the things you have to pay for.";
var w50="Partnership";
var def50="A partnership is where two or more people own and run a business.";
var w51="Permission";
var def51="Permission is where you ask if you can do something. If you ask and the person, group or council and they say yes, you have permission.";
var w52="Permit";
var def52="A permit is a special license or permission to do something";
var w53="Personal assets";
var def53="Personal assets are things that you own, like your car, house and furniture.";
var w54="Personal protection";
var def54="Being part of a company offers the shareholders some personal protection from legal and debt liabilities. This means that they have less responsibility than a Sole trader.";
var w55="Photo identification";
var def55="Photo Identification is a document that shows who you are and has your photo on it, like a Driver’s License, 18+ card or a passport.";
var w56="Postal address";
var def56="Your postal address is the address where you get your mail sent. It might be different to the address where you live.";
var w57="Pricing structure";
var def57="Pricing structure is where prices for something can change depending on how much the customer orders. The bigger the order the cheaper the price becomes.";
var w58="Private";
var def58="Private means not part of government.";
var w59="Profitable";
var def59="Profitable means that there is money left over after a business pays for all of its expenses out of the money it has made.";
var w60="Promote";
var def60="When you promote something you try to advertise or increase the amount of people who know about it.";
var w61="Public liability insurance";
var def61="Public Liability Insurance gives legal protection to the business owner against getting sued by a member of the public for things like injury or property damage. ";
var w62="Quickbooks";
var def62="Quickbooks is financial management software for business. ";
var w63="Registered";
var def63="Registered means that you have recorded your information on an official list. You register your car to be able to drive it on the road.";
var w64="Regulations";
var def64="Regulations are rules or laws that control what you can and can’t do.";
var w65="Retail";
var def65="Retail is where things get sold in small amounts to customers. Retail usually happens in a shop and the prices are higher.";
var w66="Service";
var def66="A Service business provides a service, like lawn mowing or accounting services.";
var w67="Shareholders";
var def67="Shareholders are people that own part of a company.";
var w68="Sole trader";
var def68="A sole trader is where one person owns and runs a business.";
var w69="Start up budget";
var def69="A Start Up Budget is the first Budget that gets done for a starting business and includes all of the costs involved in setting up the business.";
var w70="strategy";
var def70="A strategy in business is a plan of attack, or a plan of how to get something done.";
var w71="system";
var def71="A system is business is a set of detailed plans and rules for how to do something in your business.";
var w72="Vision";
var def72="Vision in business is being able to imagine and see something in the future. To set up a new business you need to be able to see something new that wasn’t there before.";
var w73="Wholesale";
var def73="Wholesale is where things get sold in large amounts, usually for a cheaper price. The Wholesale price. A wholesaler is usually a big shed where goods are stored. Wholesale is not usually available to just anyone.";

no, that's not a reason you would use a class file.
anyway, your document class variables are defined on the main timeline so to reference them from any timeline you can use:
MovieClip(root).w36; // for example (but it's really undesirable to have coding in more than one timeline)

How to use Forms Default Database Connection in java class

When a form based application is started, a connection is made with underlying database. This is the Default (Primay) Database Connection.
The problem is I have some of my business logic implemented in a java class. In this class I have to make a another connection with the same database. What I want to do is to use the original Database Connection in the java class. In this I may avoid the overhead of reconnection.
Could anyone pls guide me in this way...

you can't share the forms connection. Sorry :(

How to cast an object to a class known only at runtime

I have a HashMap with key as a class name and value as the instance of that class. When I do a 'get' on it with the class name as the key, what I get back is a generic java.lang.Object. I want to cast this generic object to the class to which it belongs. But I don't know the class at compile time. It would be available only at runtime. And I need to invoke methods on the instance of this specifc class.
I'm not aware of the ways to do it. Could anybody suggest/guide me how to do it? I would really appreciate.
Thanks a lot in advance.

Thanks all for the prompt replies. I am using
reflection and so a generic object is fine, I guess.
But a general question (curiosity) specific to your
comment - extraordinarily generic...
I understand there's definitely some overhead of
reflection. So is it advisable to go for interface
instead of reflection?
Thanks.Arguments for interfaces rather than reflection...
Major benefit at run-time:
Invoking a method using reflection takes more than 20 times as long without using a JIT compiler (using the -Xint option of Java 1.3.0 on WinNT)... Unable to tell with the JIT compiler, since the method used for testing was simple enough to inline - which resulted in an unrealistic 100x speed difference.
The above tests do not include the overhead of exception handling, nor for locating the method to be executed - ie, in both the simple method invocation and reflective method invocations, the exact method was known at compile time and so there is no "locative" logic in these timings.
Major benefit at compile-time:
Compile-time type safety! If you are looking for a method doSomething, and you typo it to doSoemthing, if you are using direct method invocation this will be identified at compile time. If you are using reflection, it will compile successfully and throw a MethodNotFoundException at run time.
Similarly, direct method invocation offers compile-time checking of arguments, result types and expected exceptions, which all need to be dealt with at runtime if using reflection.
Personal and professional recommendation:
If there is any common theme to the objects you're storing in your hashtable, wrap that into an interface that defines a clear way to access expected functionality. This leaves implementations of the interface (The objects you will store in the hashtable) to map the interface methods to the required functionality implementation, in whatever manner they deem appropriate (Hopefully efficiently :-)
If this is feasible, you will find it will produce a result that performs better and is more maintainable. If the interface is designed well, it should also be just as extensible as if you used reflection.

I need a clarification : Can I use EJBs instead of helper classes for better performance and less network traffic?

My application was designed based on MVC Architecture. But I made some changes to HMV base on my requirements. Servlet invoke helper classes, helper class uses EJBs to communicate with the database. Jsps also uses EJBs to backtrack the results.
I have two EJBs(Stateless), one Servlet, nearly 70 helperclasses, and nearly 800 jsps. Servlet acts as Controler and all database transactions done through EJBs only. Helper classes are having business logic. Based on the request relevant helper classed is invoked by the Servlet, and all database transactions are done through EJBs. Session scope is 'Page' only.
Now I am planning to use EJBs(for business logic) instead on Helper Classes. But before going to do that I need some clarification regarding Network traffic and for better usage of Container resources.
Please suggest me which method (is Helper classes or Using EJBs) is perferable
1) to get better performance and.
2) for less network traffic
3) for better container resource utilization
I thought if I use EJBs, then the network traffic will increase. Because every time it make a remote call to EJBs.
Please give detailed explanation.
thank you,
sudheer

Please suggest me which method (is Helper classes or Using EJBs) is perferable :
1) to get better performance
EJB's have quite a lot of overhead associated with them to support transactions and remoteability. A non-EJB helper class will almost always outperform an EJB. Often considerably. If you plan on making your 70 helper classes EJB's you should expect to see a dramatic decrease in maximum throughput.
2) for less network traffic
There should be no difference. Both architectures will probably make the exact same JDBC calls from the RDBMS's perspective. And since the EJB's and JSP's are co-located there won't be any other additional overhead there either. (You are co-locating your JSP's and EJB's, aren't you?)
3) for better container resource utilization
Again, the EJB version will consume a lot more container resources.

How to load a class from a jar not in the classpath

I have a gazillion jars of class files that I want to access dynamically in an application. I don't want to list every jar. The jars also contain images. With images you can explicitly point to the jar with and load the image with createImage....
"jar:file:/C:/myjarlocation/myjar.jar!/pathtoimage/image.gif"
Is there a similar string you can use when creating classes on the fly in a classloader with getClass().forName("classname") ??

Hm, if you are not in an EJB container or some other environment that won't let you create a classloader, you might create a new URLClassLoader with a path pointing to those JARs. You will probably want to use your normal application class loader as the parent loader, so any referenced common class definitions are found during the load.
Note that - in order to make use of the classes - you will normally need to know that they implement some interface (or inherit from a common base class) to which you can cast their instances. These Interfaces/base classes will have to be packaged for normal loading by your application class loader; else the cast will trigger an error during compile time. After this, loading them dynamically during runtime is no longer an option since they are referenced directly in the sourcecode.
Alternatively you might do away with interfaces/base classes and call methods of dynamically loaded classes also dynamically: via reflection. But I guess this is too cumbersome for what you might have in mind. Also it has more invocation overhead, less type safety and handling all these exceptions wrapped in InvocationTargetExceptions can quickly become a nightmare too...

Class overhead

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