Dynamic programming accessing static method on classes

Hi
I need access to a static method on a class.
The class name is first decided at runtime.
How do I do that?
Regards,
Morten

Hello Morten
Here is a sample program for you:
*& Report ZUS_SDN_DYNAMIC_METHOD_CALL
REPORT zus_sdn_dynamic_method_call.
DATA: go_msglist    TYPE REF TO if_reca_message_list.
DATA: gd_method     TYPE tmdir-methodname,
      gd_class      TYPE seoclsname.
START-OF-SELECTION.
IF ( 1 = 2 ).
    CALL METHOD cf_reca_message_list=>create
*      EXPORTING
*        id_object    = 'RECA'
*        id_subobject = 'MISC'
*        id_extnumber =
      RECEIVING
        ro_instance = go_msglist.
    go_msglist = cf_reca_message_list=>create( ).
ENDIF.
gd_class = 'CF_RECA_MESSAGE_LIST'.
gd_method = 'CREATE'.
CALL METHOD (gd_class)=>(gd_method)
    RECEIVING
      ro_instance = go_msglist.
IF ( go_msglist IS BOUND ).
    WRITE: / 'Class is bound'.
ELSE.
    WRITE: / 'Class is NOT bound'.
ENDIF.
END-OF-SELECTION.
Obviously, that is only half of the task. You need to make the method signature dynamically as well.
Regards
Uwe

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I am not able access static methods from startup class

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Well, welcome to the world of "hacked" phones. If your purchase was from the US, you obviously purchased an iPhone that is locked to a US carrier. The iPhone must have been jailbroken and unlocked via software to accommodate your foreign SIM card. Now that you have updated the phone, it is locked back to the US carrier. Only the carrier can authorize Apple to unlock the iPhone and none of the US carriers will unlock the iPhones. Best suggestion is to sell the phone and obtain a factory unlocked version directly from the Apple store.
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For example:
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Static methods inside class in jsp can't make it work

Hello all i can't understand it why i can't declare the method as static method ?
public class Request{
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im geting this error :
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or other sulotion for me not to make instences of class's but to use the class static methods?

Hi, try this:
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Message was edited by:
Adelx

I really need abstract static methods in abstract class

Hello all.. I have a problem,
I seem to really need abstract static methods.. but they are not supported.. but I think the JVM should implement them.. i just need them!
Or can someone else explain me how to do this without abstract static methods:
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abstract static Y getY();
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class B extends A {
static Y getY() { return YofB; }
class C extends A {
static Y getY() { return YofC; }
// code that actually uses the classes above:
// these are static calls
B.getX();
A.getX();I know this wont compile. How should i do it to implement the same?

Damn i posted this in the wrong thread.. anyways.
Yes offcourse i understand abstract and static
But i have a problem where the only solution is to use them both.
I think it is theoretically possible ot implement a JVM with support for abstract static methods.
In fact it is a design decision to not support abstract static methods.. thats why i am asking this question.. how could you implemented this otherwise?
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Can't get ClassLoader from static method.

I'm trying to get the ClassLoader within a static method getInstance().
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Bernie

Sorry for the confusion. I wrote a couple of more test programs and was able
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my intial tests were messed up...
getClassLoader() executed from a static method always returns null (in WL as
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In this case ClassLoader.getSystemClassLoader() will return a valid class
loader.
Thanks for your help.
Bernie
"Rob Woollen" <[email protected]> wrote in message
news:[email protected]..
Bernhard Lenz wrote:
I tried that as well, but getClassLoader() still returns null when
executed
in WL.
I'm still not clear how getClassLoader() gets affected by running withinWL.
>>
>
Very odd. Where is this class located? in the server's classpath, in ajar or
war file? Does getClass().getClassLoader work from a non-static method inthis
class?
-- Rob
"Rob Woollen" <[email protected]> wrote in message
news:[email protected]..
You want PropertyManager.class.getClassLoader()
-- Rob
Bernhard Lenz wrote:
I'm trying to get the ClassLoader within a static method
getInstance().
>>>>
public class PropertyManager {
public static PropertyManager getInstance(String fileName) {
//The following line returns null
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URL url = cl.getResource(fileName);
etc...
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null
is returned instead of a valid ClassLoader.
The same code executed from a standalone java program (e.g. from
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Why does getClassLoader behave differently in WebLogic than in astandalone
java program?
Thanks for you help.
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Dynamic Programming - RTTC - Appending lines

I give up! Maybe someone else can help me with this Dynamic Programming problem.
I am using RTTC to create an itab. Now I want to append lines and for some reason can't seem to crack the syntax I need.
My latest attempt looks like this...
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                           <row> TYPE ANY.
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The syntax check I get on the APPEND statement is "You cannot use explicit or implicit index operations on tables with type "ANY TABLE".
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Any help it appreciated.
Thanks
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Hello Graham
The solution is quite simple (at least to overcome your syntax error):
FIELD-SYMBOLS:
<gt_itab>     TYPE STANDARD TABLE, " use STANDARD instead of ANY
<gs_struc>    TYPE ANY.
*& Report Z_RTTI_CREATE_COMPLEX_ITAB
*& NOTE: revised version of ZUS_SDN_RTTI_CREATE_STRUCTURES
*& Thread: Dynamic Programming - RTTC - Appending lines
*& <a class="jive_macro jive_macro_thread" href="" __jive_macro_name="thread" modifiedtitle="true" __default_attr="980407"></a>
REPORT z_rtti_create_complex_itab.
TYPE-POOLS: abap.
DATA:
celltab          TYPE lvc_t_styl. " becomes field of complex itab
DATA:
gd_tabnam        TYPE string,
gd_tabfield      TYPE string,
go_table         TYPE REF TO cl_salv_table,
go_sdescr        TYPE REF TO cl_abap_structdescr,
go_sdescr_new    TYPE REF TO cl_abap_structdescr,
go_tdescr        TYPE REF TO cl_abap_tabledescr,
gdo_data         TYPE REF TO data,
gdo_handle       TYPE REF TO data,
gs_component     TYPE abap_compdescr,
gs_comp          TYPE abap_componentdescr,
gt_components    TYPE abap_component_tab.
FIELD-SYMBOLS:
<gt_itab>     TYPE STANDARD TABLE,
<gs_struc>    TYPE ANY.
PARAMETER:
p_tabnam      TYPE tabname DEFAULT 'KNB1'.
START-OF-SELECTION.
" Describe structure
go_sdescr ?= cl_abap_structdescr=>describe_by_name( p_tabnam ).
gd_tabnam     = go_sdescr->get_relative_name( ).
" Simulate dynamic addition of columns
LOOP AT go_sdescr->components INTO gs_component.
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ENDLOOP.
"   Create instances of dynamic structure and dynamic internal table
go_sdescr_new = cl_abap_structdescr=>create( gt_components ).
go_tdescr      = cl_abap_tabledescr=>create( go_sdescr_new ).
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CREATE DATA gdo_handle TYPE HANDLE go_sdescr_new.
ASSIGN gdo_handle->* TO <gs_struc>.
CREATE DATA gdo_handle TYPE HANDLE go_tdescr. " !!!
ASSIGN gdo_handle->* TO <gt_itab>.
APPEND INITIAL LINE TO <gt_itab> ASSIGNING <gs_struc>.
TRY.
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        IMPORTING
          r_salv_table = go_table
        CHANGING
          t_table      = <gt_itab>.
      go_table->display( ).
    CATCH cx_salv_msg .
ENDTRY.
END-OF-SELECTION.
Regards
Uwe

The purpose of static methods ....?

In lay mans terms can anyone tell me WHY we have static methods ?

In lay mans terms can anyone tell me WHY we have
static methods ?Static methods become class level methods and are no longer confined within the objects of the class.
Static methods typically provide information about the class as a whole, such as the number of created objects etcetera. Another use is as an object factory. Instead of doing new all over the program you have a static create method you call to get new objects of the class.

Static Method Mystry

Static methods are class spacific

By mistake First message was posted by me Sorry........
Static methods are class spacific these methods are not overridable by sub class,
But if i write
class Super{
public static void printFunction(){
System.out.println("In Super Class Method");
public class SubClass extends Super{
private static void printFunction(){
System.out.println("In Super Class Method");
}compiler gives me error
c:>javac SubClass.java
SubClass.java:12: printFunction() in SubClass cannot override printFunction() in
Super; attempting to assign weaker access privileges; was public
private static void printFunction(){
1] Why he is trying to override the printFunction() Which is static?
2] if it is not overriding then why this error comes?
Edited by: rahul_p on Apr 28, 2008 7:45 AM

Static method vs synchronisation

Hi,
A fundamental query.
If i am declaring a method as static, can i also declare it as sunchronized? i.e. can i have something like
public static synchronized sss(){
xxx
If a method is static, there is only one instance in the memory. Correspondingly, only one client can execute it at a time. in which case it is automatically synchronized.
Pl correct my reasoning.
When do we have the requirement of having a static method, or probably a singleton??
Thanks,
Prashant Gupta

Hi,
A fundamental query.
If i am declaring a method as static, can i also declare it as sunchronized? i.e. can
i have something like
public static synchronized sss(){
xxx
}?Yes, static methods can be synchronized which means that when any thread is running within a synchronized static method of class C, no other thread may enter a static synchronized method of that class. In other words, the monitor acquired by a static synchronized method is the Class itself while the monitor acquired by a non-static synchronized method is the object refered to by 'this'.
If a method is static, there is only one instance in the memory. Correspondingly,
only one client can execute it at a time. in which case it is automatically synchronized.There is (in most circumstances) a single copy of the definition (bytecodes representing all methods - static or not - and static fields) of of a class. However, any number of threads may be executing within any section of code unles that code is guarded by a synchronized block or within a synchronized method. In that case, no two threads can enter (well, actually be runnable within - Object.wait() has special implications) a synchronized block monitored by the same object.
When do we have the requirement of having a static method, or
probably a singleton??Not sure what you are asking here. You define static methods when there is behavior you want to implement that does not need to have access to instance (non-static) fields or methods and which would never need to be overridden (for purposes of polymorphism) by derived classes.
Wen needing a singleton, you have a choice of defining a "true singleton" (i.e. a class with a private constructor, some sort of static getInstance() method, with the bulk of its methods anf fields are non-static) or defining a class whose methods are all static and whose fields are also all static. Singletons. Use the one that fits you needs the best.
Chuck

How to call a static method from an event handler

Hi,
I'm trying to call a static method of class I designed. But I don't know how to do it. This method will be called from an event handler of a web dynpro for Abap application.
Can somebody help me?
Thx in advance.
Hamza.

To clearly specify the problem.
I have a big part code that I use many times in my applications. So I decided to put it in a static method to reuse the code. but my method calls functions module of HR module. but just after the declaration ( at the first line of the call function) it thows an exception. So I can't call my method.

Using static methods to instantiate an object

Hi,
I have a class A which has a static method which instantiates it. If I were to instantiate the class A twice with it's static method within class B then you would think class B would have two instances of class A, right?
Example:
class A
   static int i = 0;
   public A(int _i)
       i = _i;
   public static A newA(int _i)
        return new A(_i);
class B
    public B()
        A.newA(5);
        A.newA(3);
        System.out.println(A.i);
    public static void main(String[] args)
        B b = new B();
}Is there really two instances of class A or just one? I think it would be the same one because if you check the int i it would be 3 and not 5. Maybe static instantiated objects have the same reference within the JVM as long as you don't reference them yourself?
-Bruce

It
seems like you are the only one having trouble
understanding the question.Well I was only trying to help. If you don't want any help, its up to you, but if that's the case then I fail to see why you bothered posting in the first place...?
Allow me to point out the confusing points in your posts:
you would think class B would have two
instances of class A, right?The above makes no sense. What do you mean by one class "having" instances of another class? Perhaps you mean that class B holds two static references to instances of Class A, but in your code that is not the case. Can you explain what you mean by this?
Is there really two instances of class
A or just one?You have created two instances.
>I think it would be the same one because if you
check the int i it would be 3 and not 5.
I fail to see what that has to do with the number of instances that have been created...?
Maybe static instantiated objects have the
same reference within the JVM as long as you
don't reference them yourself????? What is a "static instantiated object"? If you mean that it was created via some call to a static method, then how is it different to creating an object inside the main method, or any other method that was called by main? (i.e. any method)
What do you mean by "the same reference within the JVM"? The same as what?
What happened to the first call "A.newA(5)"?
I think it was overidden by the second call
"A.newA(3)".As i already asked, what do you mean by this?
If you change the line for the constructor
in A to i = i * i you will get "9" as the
output, if you delete the call "A.newA(3)"
you will get "25" as the output. Yes. What part of this is cauing a problem?

Campaigns with static method

I have two questions regarding campaign
1)I have configured campaign for update events of content.
which will call static method of one class.but when any update occur in repository,exception comes for static method's class not found.
2)How to avoid stop date in campaign.so that it will run always.
Can anybody help me on the same

Since the campaigns run in the enterprise app classloader, anything called by the campaign needs to run in this classloader as well (APP-INF/lib). You could perhaps promote the code you want to call from the campaign from the web-app classloader to the enterprise-app classloader if you want it to be called.
Code in the enterprise-app classloader (APP-INF/...) can be called by code in the web-app classloader (WEB-INF/...) but not vice-versa. So it shouldn't be an issue to move the code to the ent-app classloader, and it can then be called by both the campaign as well as existing web-app code.
-Steve

Static methods in interfaces

Java cognoscenti,
Anyone know why I can't declare a method as static in an interface, but I can in an abstract class. Surely, semantically it's the same - defering the implementation of a static method, not an abstract class and an interface. By the way, I'm using JDK 1.2.2 if that makes a difference

No, it's not the same. You are not "defering the
implementation of a static method" because static
methods are never polymorphic.
Static methods cannot be abstract for this reason, and
only abstract methods are allowed in interfaces.I didnt't know that. I thought that - because you can override static methods and you can call them onto an actual instance the method binding would be done at run-time, not at compile-time. So I was trying to prove you wrong, but you are correct !
A short summary of what I've learnt so far:
- interfaces cannot contain static methods
- abstract classes cannot contain abstract static methods
- static methods can be overriden, but they are not polymorphic; this means that the compiler decides which method to call at compile-time.
/* output
SuperClass.someMethod()
SubClass.someMethod()
SuperClass.someMethod()
SuperClass.someMethod()
SubClass.someMethod()
SubClass.someMethod()
SuperClass.someMethod()
public class Test {
public final static void main(String[] args) {
      // output: SuperClass.someMethod()
      new SuperClass().someMethod();
      // output: SubClass.someMethod()
      new SubClass().someMethod();
      // output: 2x SuperClass.someMethod()
      SuperClass someClass1 = new SubClass();
      someClass1.someMethod();
      showSuper(someClass1);
      // output: 2x SubClass.someMethod()
      SubClass someClass2 = new SubClass();
      someClass2.someMethod();
      showSub(someClass2);
      showSuper(someClass2); // SuperClass.someMethod()
public final static void showSuper(SuperClass c) {
        c.someMethod();
public final static void showSub(SubClass c) {
        c.someMethod();
class SuperClass {
public static void someMethod() {
    System.out.println("SuperClass.someMethod()");
class SubClass extends SuperClass {
public static void someMethod() {
    System.out.println("SubClass.someMethod()");

Static method or not static method

I have a simple class, ClassA, with no shared class variables, and has only one static method only:
class ClassA {
public static void doIO (args) {
try {
//very time consuming I/O task
catach (Exceptions e) {
//try to resolve the problem
This doIO method will be called simultaneously from different objects.
My questions are:
1) Would this static method approach cause any robustness, efficiency problem? Or, should I change the method into a non-static method, and create a new instance of ClassA every time?
2) If there are 20 threads call ClassA.doIO(args) at the same time, would the method be executed in parallel or queued?
Many thanks.
java9394

Using a static method makes this implementation as efficient as possible. Since the class has no instance variables, there is no benefit, to either making it non-static, or creating multiple instances. If you have 20 threads calling it, they will run concurrently. So, if you do not like this behavior, the method can be declared both static, and synchronized.

Dynamic programming accessing static method on classes

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