Parameter or static method?

(i'm braziliam, sorry for any english mistake..)
Imagine a object A, that contains a object B, that contains a object C, and so on...
Imagine that the object Z needs to use a table that A object contains.
Now, imagine All the people, leaving for today!.. (kidding.. lol)
Ok, my question is:
What is most corret/secure/usual to do?
Pass the A's table (or self A object) to B's constructor, and from B to C, and so on until Z get it.
Or create a static method A.getTable()?
I like the idea of the static method, but I hear to avoid static methods....
What do you say?

if starsCount is a static parameter of Universe then the static method works fine.... but notice, if you assume there are multiples universes (that is, if your class A can have multiple instances, and that each instance has its own parameters), it won't work.
Since we are supposing there are only one universe we can take your analogy one level below: suppose your Planet class has a parameter double mass. And the planet has cities, etc.... and then the human wants to know his planet's mass. Your static method solution will definitely not work here, unless you (strangely) assume "mass" is a static parameter of Planet class.... right?
By the way, I'm brazilian too.... nice to know there are other brazilians here :D Let's keep it in english though right?

Similar Messages

Regarding Returning Parameter and Static method

Hi frnds,
I am learning oops ABAP. I want to use returning parameters in method and also STATIC METHOD.
If any example it will be more helpful
regards,
satya

Hi satya,
             Check this out ,Its helpful.
To get some values from a method , one can use the exporting, changing or returning parameters.If one uses RETURNING parameters, the following restrictions apply:-(1) No EXPORTING/CHANGING parameters can be used for the method.(2) Only one RETURNING parameter can be used.(3) RETURNING parameters are only passed by value.This program demonstrates the use of RETURNING parameters and the various ways   to call a method with RETURNING parameter to get the value into some variable.
Sample Program
</code>
report ysubdel1 message-id 00.
data : w_num type i.
class c1 definition .
public section.
methods : m1 importing input1 type i
                        input2 type i
                        returning value(result) type i .
endclass.
class c1 implementation.
method : m1.
result = input1 * 2 + input2.
endmethod.
endclass.
start-of-selection.
data : obj1 type ref to c1 .
create object obj1.
Syntax 1
call method obj1->m1 EXPORTING input1 = 5                                                        input2 = 4
                               RECEIVING result = w_num.
write:/5 w_num .
Syntax 2
     w_num = obj1->m1( input1 = 10 input2 = 20 ).
write:/5 w_num .
Syntax 3
move obj1->m1( input1 = 2 input2 = 3 ) to w_num .
write:/5 w_num .
</code>
Static method example
<code>
REPORT zstatic.                              .
data : num type i.
class testclass definition.
public section.
class-methods : testmethod.
endclass.
class testclass implementation.
method : testmethod.
num = 5.
write:/5 num.
endmethod.
endclass.
start-of-selection.
call method testclass=>testmethod.
</code>
Reward Points if u find helpful.
Thnks & Regards,
Rajesh

Calling a java static method from javascript

I am running into issue while calling a java static method with a parameter from javascript. I am getting the following error. Any help is greatly appreciated.
Thx
An error occurred at line: 103 in the jsp file: /jnlpLaunch.jsp
pfProjectId cannot be resolved to a variable
=================================================
// Java static method with one parameter
<%!
public static void CreateJnlpFile(String pfProjectId)
%>
//Script that calls java static method
<script language="javascript" type="text/javascript">
var pfProjectId = "proj1057";
// Here I am calling java method
<%CreateJnlpFile(pfProjectId);%>
</script>
===================================================
Edited by: 878645 on Mar 6, 2012 11:30 PM

Thanks, Got what you are telling. Right now I have one jsp file which is setting the parameter 'pfProjectId' and in another .jsp I am retrieving it. But I am getting null valuue
for the variable. I am wondering why I am getting null value in the second jsp page?.
Thx
====================================================================
<script language="javascript" type="text/javascript">
// Setting parameter pfProjectId
var pfProjectId = "proj1057";
request.setParameter("pfProjectId", "pfProjectId");
</script>
// Using Button post to call a .jsp that creates jnlp file
<form method=post action="CreateJnlpFile.jsp">
<input type="submit" value="Create JNLP File">
</form>
//Contents of second .jsp file CreateJNLPFile.jsp
String pfProjectId = request.getParameter("pfProjectId ");
System.out.println( "In CreateJnlpFile.jsp pfProjectId " + pfProjectId );
=======================================================

Should I use a static method or an instance method?

Just a simple function to look at a HashMap and tell how many non-null entries.
This will be common code that will run on a multi-threaded weblogic app server and potentially serve many apps running at once.
Does this have to be an instance method? Or is it perfectly fine to use a static method?
public static int countNonNullEntries(HashMap hm){
if(hm==null)return 0;
int count=0;
for(int i=0; i<hm.size(); i++) {
if(hm.get(i)!=null)
{ count++;}
return count;
OR
public int countNonNullEntries(HashMap hm){
if(hm==null)return 0;
int count=0;
for(int i=0; i<hm.size(); i++) {
if(hm.get(i)!=null)
{ count++;}
return count;
}

TPD Opitz-Consulting com wrote:
The question is the other way around: Is there a good reason to make the method static?
Ususally the answer is: no.The question is: does this method need state? Yes -> method of a class with that state. No -> static.
The good thing of having this method statig is that it meight decrese memory foot pring but unless you're facing memory related problem you should not think about that.I doubt there is any difference between the memory foot print of a static or not method.
I'm not shure if this method beeing static maks problems in multithreaded environments like the one you're aiming at. But I do know that an immutable object is always thread save.Does the method use shared state (data)? No -> no multi threaded problems.
Can the parameters be modified by different threads? Yes, if multiple threads modified the parameter map, but nothing you can do about it here (no way to force the calling thread to lock on whatever you lock on).
So my answer to your question is: yes, it should be non static.The method should be static since it uses no state.
It is thread-safe when only the calling thread can modify the passed map (using a synchronized or ConcurrentHashMap is not enough, since you don't call a single atomic method on the map).
// Better use Map instead of HashMap
// We don't care about the generic type, but that does not mean we should use a raw type
public static int countNonNullEntries(Map<?, ?> map) {
// whether to accept null map or not, no need for explicit exception
// since next statement throw NPE anyway
Collection<?> values = map.values();
// note your method is called countNonNull, not countNull!
// (original code it would need to by if(null != mapValue) notNullsCounter++;
return values.size() - java.util.Collections.frequency(values, null);
}

Need Urgent Help with static methods!!!!

If I have a static method to which a variable is being passed...for example
static String doSomething(String str)
//..doSomething with str and return
If the method is invoked a second time by a separate entity when it is already in use by one entity(!!!not entity beans) .... will this lead to the second invocation overwriting str while the method is already in use and thus corrupting the variable that the method was passed from the first entity?

It's also a common misunderstanding about parameters. The method does not receive a variable as its parameter, it receives a reference to an object. And inside the method, the parameter acts just the same as a local variable would. So if two threads call the method (static or not), each thread has its own copy of the parameter.

Static Method to calculate ' Average '.

Hi
I am wondering which one is preferred? Static or Instance methods for calculating 'average' (e.g average sales).
My class lcl_company is having attributes name and sales. which represents name = name of the company, sales = total sales of one company under department: automobiles.
eg output:
Department: automobiles.
name = abc company
sales = 1000
name = xyz company
sales = 2000
total companies added: 2.
now i want to calculate the average sales of the companies under department automobiles.
I prefer using a static method (is it good choice), if not, why instance method. while using the static method, I noticed that i need to stick just with the defined attributes.
Please advice on calculating average.
Thank you.

Hi Pawan,
There are so many ways,:
One, as you said, you defined this itab as a attribute of this Object, then you need define another attribute 'AverNum' as public. Of cause, this Object have a method using to calculate the average number, passing the value to public attribute 'AverNum', then you can access this public attribute from outside.
Another way: Define this itab as a importing parameter of your average method, same time, this average method have a return parameter. Then you can call this static object method or instance object method from outside, and return your output by return parameter.
regards,
Archer

Memory management with static methods

I made a class with no attributes and only static methods with the purpose of maintaining as little as possible about it in memory. What information is kept in memory by the JVM about such a class ?
Thanx in advance :)

Static methods don't consume less memory than regular instance
methods. Well, not exactly: a regular method requires a reference
to an instance as a hidden additional parameter. Thus, specifying
static for methods that don't access the object may actually save
a few bytes. However, the code is not duplicated for each instance.
Additionally, the JVM must keep any initialization values and the
names of the class and the methods, as needed by reflection.
Given suitable debugging options, local variables names and line
number may be kept in memory as well. Finally, all hosekeeping
info (gc, references and the like) must be kept in memory.

Find the Class Name in a static method

Hi All,
I am trying to find the class name inside the static main method. I want to write one main method that loads an instance of the class. Other folks have suggested tricks with the security manager or creating an Exception to look at the stack trace, but these methods don�t reflect the inheritance. I want SUBCLASSES to be able to run from the command line using the inherited main method.
public static void main(String args[]){
      JPanel thisJPanel = (JPanel) Class.forName(????).newInstance();
}Any Ideas

I want
SUBCLASSES to be able to run from the command line
using the inherited main method.Someone pointed this out already but more directly, static methods are not inherited.
The behavior you desire ca be achieved using the Factory pattern.
The idea of being able to subclass an application is a little bizarre. Why don't you just do something like this:
public static void main(String[] args){
    // check that there is at least one parameter
    JPanel thisJPanel = (JPanel) Class.forName(args[0]).newInstance();
}

Non-static method close() cannot be referenced from a static context

Friends,
I am having a little help with some static and not static issues.
I created a JMenuBar, it's in the file: SlideViewMenu.java
One of the operations is File->Close and another is File->Exit.
The listener is in the SlideViewMenu.java file. The listener needs to reference two non-static methods within SlideView.java.
Here's some of the code:
SlideViewMenu.java
public class SlideViewMenu {
    public JMenuBar createMenuBar() {
    final Action openAction = new OpenAction();
    Action aboutAction = new AboutAction();
    ActionListener menuListener = new MenuActionListener();
    JMenuBar menuBar = new JMenuBar();
     // All the menu stuff works fine and is taken care of here.
   // Listener for Menu
   class MenuActionListener implements ActionListener {
     public void actionPerformed (ActionEvent actionEvent) {
          String selection = (String)actionEvent.getActionCommand();
         if (selection.equals("Close"))
          SlideViewFrame.close();
         else SlideViewFrame.exit();
}SlideView.java
// Driver class
public class SlideView {
     public static void main(String[] args) {
          ExitableJFrame f = new SlideViewFrame("SlideView");
                // Stuff here, works fine.
// Frame class
class SlideViewFrame extends ExitableJFrame {
        // some things here, work fine.
     private SlideViewMenu menuBar = new SlideViewMenu();
     public SlideViewFrame(String title) {
     // Set title, layout, and background color
     super(title);
     setJMenuBar(menuBar.createMenuBar());
        // Stuff here works fine.
     // Handles doing stuff once the file has been selected
     public void setFileName(File fullFileName, String simpleName) {
        // Stuff here works fine.
     // File->Close. clean up everything.
     public void close() {
          setTitle("SlideView");
          textArea.setText("");
          scrollBar.setVisible(false);
          textArea.setVisible(false);
          statsPanel.setVisible(false);
     // File->Exit.
     public void exit() {
          System.exit(0);
}The error I'm getting is:
SlideViewMenu.java:50: non-static method close() cannot be referenced from a static context
I don't get it?
Thanks for all help.

Making close() and exit() static would not solve the problem because close() requires access to nonstatic member variables/functions.
Fortunately, that is not necessary. The real reason you are having a problem is that you don't have any way in your listener to access the main frame window, which is what the listener trying to control. You made a stab at gaining access by prefixing the function with the class name, but, as the compiler has informed you, that is only valid for static methods. If you think about it, you should see the sense in that, because, what if you had a number of frames and you executed className.close()? Which one would you close? All of them?
Fortunately, there is an easy way out that ties the listener to the frame.
SlideViewMenu.java:public class SlideViewMenu
// Here's where we keep the link to the parent.
private SlideViewFrame parentFrame;
// Here's where we link to the parent.
public JMenuBar createMenuBar(SlideViewFrame linkParentFrame)
    parentFrame = linkParentFrame;
    final Action openAction = new OpenAction();
    Action aboutAction = new AboutAction();
    ActionListener menuListener = new MenuActionListener();
    JMenuBar menuBar = new JMenuBar();
    // All the menu stuff works fine and is taken care of here.
// Listener for Menu --- It is assumed that this is a non-static nested
// class in SlideViewMenu. All SlideViewMenu variables are accessible from
// here. If this is not the case, simply add a similar member variable
// to this class, initialize it with a constructor parameter, and
// pass the SlideViewMenu parentFrame when the listener is
// constructed.
class MenuActionListener implements ActionListener
    public void actionPerformed (ActionEvent actionEvent)
      String selection = (String)actionEvent.getActionCommand();
      // Use parentFrame instead of class name.
      if (selection.equals("Close"))
          parentFrame.close();
        else
          parentFrame.exit();
}SlideView.java// Driver class
public class SlideView
public static void main(String[] args)
    ExitableJFrame f = new SlideViewFrame("SlideView");
    // Stuff here, works fine.
// Frame class
class SlideViewFrame extends ExitableJFrame
// some things here, work fine.
private SlideViewMenu menuBar = new SlideViewMenu();
public SlideViewFrame(String title)
    // Set title, layout, and background color
    super(title);
    //Here's where we set up the link.
    setJMenuBar(menuBar.createMenuBar(this));
// Stuff here works fine.
// Handles doing stuff once the file has been selected
public void setFileName(File fullFileName, String simpleName)
    // Stuff here works fine.
// File->Close. clean up everything.
public void close()
    setTitle("SlideView");
    textArea.setText("");
    scrollBar.setVisible(false);
    textArea.setVisible(false);
    statsPanel.setVisible(false);
// File->Exit.
public void exit()
    System.exit(0);
}

Export Internal table by calling static method

Hi friends,
Can u please tell me how to get internal table in export parameter by calling static method.
OR can u tell me how to declare internal table in method parameter.
Thanks in advance

Raja's method will work for all tables irrespective of the structure and is the best possible approach. However, if your requirement is simple and you do not have to deal with a lot many tables,
1. Create a Type-Pool, suppose ztypl
2. Within the type pool, declare a Structure type,
TYPES: BEGIN OF ztypl_struct1,
         "Place your fields here
       END OF ztypl_strict1,
       "Create a table of type ztypl_struct1 here
       ztypl_table1 TYPE TABLE OF ztypl_struct1.
Use "ZTYPL_TABLE1" as the "Associated type" in your method's Parameter definition in SE24.
eg.
IT_TABLE      TYPE     ZTYPL_TABLE1
If you are writing your class in an include,
    METHODS my_method1
      IMPORTING
        it_table1   TYPE ztypl_table1.
Do remember to include
TYPE-POOLS: ztypl.
in your class's Constructor / Include program.
Please award points if helpful.
Regards,
Ryan
Message was edited by:
        Ryan Cannel

Do static methods perform better

Sometimes, especially when refactoring (specifically when doing extract method), I create a method in a class to perform some helpful task or to neatly tuck a chunk of ugly code away somewhere that it can be easily referred to from the "actual" code. This new method doesn't actually directly cause a state change in the object, it just accepts a parameter and returns a value, or similar. In nearly every case this method is private (since it only helps out the class in which it appears).
I can easily declare these helper methods static, or leave them unstatic. What I'm wondering is if there's any best practice in doing one or the other, whether for performance reasons or otherwise. I'd tend not to make them static because it might imply that the method should be called from a static context or something, but I wondered what others suggest in this regard.
Thanks.

I agree with you Dubwai, and in practice will probably
not use static unless I mean it. But, since the
methods don't really act on any of the class's
instance members, I'm also not entirely convinced that
this does go against the "design" -- because
whether the method is static or not, it has the exact
same effect.
In fact, marking it static might even help make
it obvious that this method performs no side-effects
on instance members.
But again, I think I'll just leave them nonstatic.I'm not saying that you shouldn't make things static. Quite the contrary. I'm saying that things should be static if they are static, meaning they don't change polymorphically or per instance. If this is so, the method should definitely be static.
Not using instance members is a neccesary condition of being a static method but it is not nearly sufficient. Making a method static means throwing polymorphism out if the door. A method may do nothing but return a static final value but still need to be an instance method if a subclass needs to return a different static final value. If you make a method static and then need to refactor, it can be difficult or impossible to do so, as pointed out above. If you are calling static methods as if they are instance methods, that indicates to me that they probably should just be instance methods.

Static method decisions

Dear all experts,
I have got some problems understanding when to use static methods or passing the classes through constructor.
I have got a class which needs to be accessed by several classes and also the classes inside the classes etc....
Instead of passing classes around, should I just create a single static class which can be accessed by all the classes without needing to instantiate the class?
I found that, i particularly in doubt when there are classes like "TableParser", "PropertiesReader" etc which some classes deep down in the hierarchy need access to those classes...
Also, making the class static would it decrease the security of the whole program?? Say if i have got an encrytion class which does all the encrypt and decrypt, if i let it be static, isn't it easier to let people accessing the method? the same applies to properties editor etc??
Any help would be really appreciated.
Thx

thx again jverd... (remember the security question? :)
)I remember your id, but I didn't recall which thread(s) I had seen it in.
>
based on the understanding of what you said, do you
mean that, if i am only using a class to store or read
a setting file, it's ok to let it static? (so that all
classes can access it whenever they like without
passing the parser class to classes?)Um, again, you're terminology's a little off, so I'm not sure exactly what you mean, and even the description "store or read a seting file" could have a couple of interpretations.
For example....You read the file once, and the config data it constains is accessible throughout your app and never changes. This might be a candidate for a class that only had static methods, but it would be kind of inflexible. What if later some other part of your app, or some other library that you develop that your app is going to use, wants to get its configuration from a file. In that case, I might want to have a couple instances of that class around. One for the global config that reads one file, and another for the config for that library that might read another file.
I'd probably not even think about it as "reading a settings file." Rather, I'd see that as two parts: providing config settings to the app via a class, and reading a file to populate that class. The settings would exist independent of the fact that you can populate them from a file.
I'd think about how I want to use them and decide whether to instantiate the class or use static methods based on that. Separately, I'd think about how this class or an instance of it is gonna get popuated with data from outside the program.
I might decide to have different instances hold different sets of config data, and therefore use instance (non-static) methods to access the data in each of those instances, but I might register the instances--say by name, or maybe just in a list--and I could use a static method to acess the map or list: Config dbConfig = Config.getConfig("database"); Also, I wouldn't generally make a decsision on whether to use class methods or instance methods based on not having to pass a parameter.
If you're thinking "I'd like to use static because it's easier. Can I get away with it here," then you're viewing objects as a burden to be avoided, which kind of defeats the purpose of using OO techniques in the first place.

Is(are) there any static method(s) available for number checking?

I want to check some texts entered by user whether it is a number or not but I want to do it with a static method which takes the texts as parameter returns a boolean true or false value. So if anyone has any solution plz help!!!

I want to check some texts entered by user whether it
is a number or not but I want to do it with a static
method which takes the texts as parameter returns a
boolean true or false value. So if anyone has any
solution plz help!!!How does the user enter the text? It's much better to e.g. limit the possibility to enter illegal characters.
Kaj

Access to Class information from a static method

There does not appear to be anyway to access the Class object from instead a static method.
e.g. How could I convert the following code so that it works ?
class test {
static void printClassName() {
System.out.println( getClass().getName() );

The idea was to have a static method that could be
used to make a lookup based on the classname. Being
able to access the class name would mean that I would
not have to reimplement for every subclass !!!!!Hmm.. what are you trying to look up? Some kind of class-specific constant information maybe?
In general your best bet is to define an abstract method in your parent class for return of the constant value, then define a specific method in each sub-class that overrides it, retrurning the appropriate value.
Then you're common processing just gets the value with that method.
Using some kind of lookup on the basis of class name is much clumsier, and more inclined to run time errors. Better to use the built in virtual methods table.
Another approach is to have the value as a parameter of the constructor of the parent class and use "super(value)" in the child classes to store
it.

Reflextions within static methods

I need to know the name of the class within a
static method.
In an instance method I can just use
this.getClass(), but not in a static method.
I need it because I have a class that inherits
from a singleton. But I can't use the inherited
static method getInstance(), it gives me
in instance of the superclass.

I don't want to overwrite "instance" and "getInstance()",
I only want to use them in the context of the Class "Something".
Here is my next approach to the Idea:
abstract public class Singelton {
     static Singelton instance = null;
     static Singelton getInstance(Class thisClass)     {
       if(instance == null)
          try {
            Constructor constructor = thisClass.getConstructor();
            instance = (Singelton)constructor.newInstance();
       } catch (Exception e) {
          e.printStackTrace();
       return instance;
     abstract public void doSomething();
public class Something extends Singelton {
     public void doSomething()
          System.out.println("Hello world!");
     public static void main(String[] args)
          Singelton s = Something.getInstance(Something.class);
          s.doSomething();
}The only little thing is, I would like to avoid
the parameter "thisClass" in the method "getInstance()",
because the method getInstance() in the class Singelton
is call thru the class Something.

Parameter or static method?

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