Are private methods inherently final?

You can�t override a private method, so is it inherently final? Will the compiler treat it like a final? I�ve heard that final methods may be inlined by the compiler but haven�t really been able to produce a test to show the advantage of inlining. I know in theory it trades speed for program size, but, if it does work, is it really that much faster? I�m guessing CPU local cache probably eliminates or at least reduces to negligible time the overhead of swapping out the instruction stack to perform a �jump.�
Thanks for your thoughts. Mostly trying to figure out when to use final methods.

You can�t override a private method, so is it
inherently final? Given that that is exactly what the JLS says it would
suggest that the answer is yes.
http://java.sun.com/docs/books/jls/second_edition/html
/classes.doc.html#38958
I believe the invocation (byte code) is different as
well (but I didn't look it up) so the VM could
certainly easily do something with it.Actually, I don't think this is 100% accurate.
You can replace a private method in a subclass with the same signature (name, arg list) with the same return type. In fact, this is true even if the private method is declared final. It is only when the final method is public (maybe protected and package, I'm not sure) that the compiler complains when you try to extend it.
� {�

Similar Messages

Are private members inherit or not??

Hi, I read the Sun Java tutorial twice times in this year about this topic.
March 2006, it says:
"A subclass inherits all the members variables and methods from its superclass. However the
subclass might not have access to an inherited member variable or method. For example a
subclass cannot access a private member inherited from its superclass. One might think ,then ,
that the item was not inherited at all. But the item is inherited."
September 2006, it says:
"A subclass does not inherit the private members of its parent class. However, if the superclass
has public or protected methods for accessing its private fields, these can also be used by the subclass.
A nested class has access to all the private members of its enclosing class�both fields
and methods. Therefore, a public or protected nested class inherited by a subclass has indirect access
to all of the private members of the superclass".
Which is wrong? Are private members inherit or not??

I teach Java 101 now and then. When I describes classes, sub-classes and access modifyers I use this metaphor:
Look at a class as a cardboard box. On the left outside of the box, you can write the names of the methods and attributes that you want others to see. These are the ones marked with public.
On the bottom outside of the box, you write all the names of attributes and methods that can be seen by classes that extends your class, sub-classes. These are the ones marked with protected.
Somehow, you are able to read the text on the outside when standing inside the box... has something to do with the pen that you use... ;-)
On the inside of the box you can write whatever you want that you do not want anyone else to see. These are marked private.
When creating a sub-class the sub-class-boxes are designed in such a way that it has a glass shelf halfway up on the right wall where you place your super-class-cardboard-box and a small window that allows users on the outside to look at the left side of the super-class-box. That is the only difference between a sub-class and a super-class-box.
Standing outside of the sub-class-box, you can read the left side of the sub-box and the left side of super-box through the window.
Standing inside the box, you can also read the bottom of the super-box through the glass-shelf.

Final&private methods in inheritance

Hi all,
We know that in inheritance private methods are not inherited by sub classes. In addition to this it's also known that final methods are inherited but cannot be changed. Then what is the use of using private methods when there is final methods which cannot be changed, that is why to hide our methods, are they(private methods) something that must be encapsulated as they behave like supporting methods?

Yes, you hide methods by making them private in order to hide implementation details.

Extending classes with private methods?

my understanding of extending classes is that you gain all the functions and methods of that class thus You could over ride any one of them. How ever I am confused on weather or not you inherit and can over ride private methods of the class you are extending or if you have to have all methods public in an extended class.
hope that makes sense, an example can bee seen bellow.
package
     public class Class1
          public function apples():void
               //some code
          private fnctuin bananas():void
               //more code
package
     public class Class2 extends Class 1
          override public function apples():void
               //i changed code
          //can I over ride bananas?

you can only override methods that would be inherited. a private method won't be inherited:
http://www.kirupa.com/forum/showthread.php?223798-ActionScript-3-Tip-of-the-Day/page5

Actual Benefits of final methods and final parameters

I know that a lot of this depends on the JVM and the actual code, but I was wondering what the actual real world advantage was of using final methods and final parameters.
I use a business and data layer for my program to interact with the database. So all of the methods in these classes are public and static. I was just wondering if it would be benefical to make all of these methods final and all of the parameters final also. I won't ever be making subclasses of these classes, so is this worth doing?
Thanks,
Dave Johansen

On the point of final, this should always be a design decision. That is, does it make sense to allow your class to be overridden? Making classes and/or methods final is a big barrier to future enhancements and extendability - so only make soemthing final if you haver a specific reason for doing so.
Any performance issues should not take a high precedence in this decision - and in any case the difference in making something final will be non-existant for all practical purposes.
How about volatile?
I get the meaning of synchronized but
volatile?Volatile is a keyword that tells the JVM it can't optimize / inline serctions of code that use certain variables. You may not realise it, but the JVM takes your bytecode and chops them up and re-arranges them at runtime, to boost performance. This can sometimes have dangerous consequences in a mutlithreaded environment, so by adding the volatile keyword you are saying to the JVM (or specifically HotSpot) not to perform any "code magic".
Here's a simple example:
public class TestClass {
    private boolean check = false;
    public void setTrue(){
        check = true;
    public void check(){
        check = false;
        if(check){
            System.out.println("Will this ever print?");
}Obviously the string will never print in a single threaded environment. However, in a multithreaded environment, is is possible that a thread could call setTrue() between another thread setting the value to false and performing the if() check. The point is that due to runtime optimization, Hotspot may realise that check is always false, so completely remove the code section with the if block. so regardless of the value of the boolean, the code may never be entered.
One solution is to declare the boolean check as volatile. This tells the JVM that such optimizations are not allowed and then it is entirely possible for the string to be printed.
One curiousity, off-topic:
is there a way for jvms instantiations to see each
other?Have you looked into RMI?

Enum private methods: did everyone know this but me?

Consider the following code:class C {
    final C C1 = new C() {
        public void f() {
            g();
    private void g() {
enum E {
    E1 {
        public void f() {
            g();
    private void g() {
}It struck me that the class and the enum are structurally very similar: the class has an inner class that references a private method; the enum has a value that references a private method.
But the big difference is: the enum won't compile. Unless I change the protection on g() to "protected" or less, it throws an error.
And the bizarre part is, the error is not "g has private access" or "cannot find symbol". No, it's "non-static method g() cannot be referenced from a static context"! WTF?
I solved the mystery by utter accident, when I changed the class to class C {
    static final C C1 = new C() {
        ...That is, I made the variable referring to the instance of the inner class static. That made the class fail to compile with the same "static context" error I saw in the enum.
It took several minutes of open-mouth staring at the screen to get it: in the original class, the g() being called was not in the same object, but in the outer object. Methods of object declared in a derived class cannot get to private members, even of the same object, declared in an ancestor class: that is the meaning of the word "private". But methods of an inner class can get to private members of the outer class. So in the original class, the inner-object could not see its own g(), so it looked at the outer-object's g(); when I changed the inner-object to static, there was no outer object, and I got an error to that effect.
Enum values are basically solitary instances of static inner classes of the class representing the enum itself and so, in the same situation produce the same error message.
Oddly, the following does compile:enum E {
    E1 {
        public void f() {
            E1.g();
    private void g() {
}That is, instead of accessing g() as E.this.g(), I accessed it statically as E.E1.g(). In fact, this was the first thing I tried -- under the wrong impression that f() was static within E1, not the E1 was static within E. In retrospect, I can see why it works, but I cannot explain it properly or defend it intellectually.
Who sez Java ain't fun?
M.

It took several minutes of open-mouth staring at the
screen to get it: in the original class, the g()
being called was not in the same object, but in the
outer object. Methods of object declared in a
derived class cannot get to private members, even of
the same object, declared in an ancestor class: that
is the meaning of the word "private".There's a problem with this theory. Consider the following:
class C {
    protected String s = "C";
    public static final C C1 = new C() {
        public void f() {
            s = "C1";
            C.C1.g();
    private void g() {
        System.out.print(s);
    public void f()
        System.out.println("C.f()");
}Then a main method like so:
    public static void main(String[] args) {
        try {
            C.C1.f();
        } catch (Exception exception) {
            exception.printStackTrace();
output:
[pre]
C1This can be changed to:
    public static final C C1 = new C() {
        public void f() {
            s = "C1";
            ((C)this).g();
    };To acheive the same effect. You can make C1 an instance, but you cannot run the example because it will throw a StackOveflow exception.
So to run the original example, we have to Change C to:
class C {
    static int count;
    protected String s = "C";
    public C()
        if (count++ < 2) C1 = new C() {
            public void f() {
                s = "C1";
                ((C)this).g();
        else C1 = null;
    public final C C1;
    private void g() {
        System.out.print(s);
    public void f()
        System.out.println("C.f()");
}now the main body becomes:
new C().C1.f();Output:
C1So the point is that the method is not called on the outer instance. The problem is with access and how the compiler is creating the code to fuflill the syntactic sugar of inner classes and nested classes.
One rule says the subclass doesn't have access to call the g() method defined in the parent class. The other rule says that it does because it's an inner class. So C1 can call g() on a C instance but not on an instance of it's anonymous class. This is a contradiction as the anonymous class instance is a C. Whether this follows the JLS (therefore not a bug) I think it's still a flaw. Try casting C1 to a C in the enum example and see if it resolves the issue.

How to call a private method in a JFrame

I have a Frame which has some properties like its size, bgcolor plus other parameters, as instance variables. There is a button on the Frame with the caption : "set properties". When one clicks on that button, a new frame should appear via which a user can change the values of the parameters of the main Frame (i.e size, bgcolor,..etc). The user would input the new values in the textfields or radio buttons that are on the new frame, and then click a submit button, which has to exist on the same NFrame. How can I do that so that when the submit button is pressed, the parameters values are updated and so is the display view ?
I made it this way : I created 2 classes, the main frame and the new Frame. I made the new Frame an instance variable of the main Frame. When the user clicks the " set properties" button on the main Frame, the new Frame is shown. The user enters new values for some of the parameters and clicks submit. The parameters in the new Frame are updated. UP TO HERE EVERYTHING WENT JUST FINE. Now, there is a private method in the main frame that changes the color, size, ...etc of the main frame according to the values stored in the instance variables color, size,...etc. THE QUESTION IS: How can the new Frame display the changes after the values have been updated ? That is, how can it call the "private" method in the main class?? Should the new class be a child class of the main class to be able to access it's private methods ??

import java.awt.*;
import java.awt.event.*;
import java.util.Random;
import javax.swing.*;
public class CallingHome
    SkinMod skinMod;
    JPanel panel;
    public CallingHome()
        // send reference so SkinMod can call methods in this class
        skinMod = new SkinMod(this);
        JButton change = new JButton("change properties");
        change.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent e)
                skinMod.showDialog();
        JPanel north = new JPanel();
        north.add(change);
        panel = new JPanel();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(north, "North");
        f.getContentPane().add(panel);
        f.setSize(300,100);
        f.setLocation(200,200);
        f.setVisible(true);
    public void setBackground(Color color)
        panel.setBackground(color);
        panel.repaint();
    public static void main(String[] args)
        new CallingHome();
class SkinMod
    CallingHome callHome;
    Random seed;
    JDialog dialog;
    public SkinMod(CallingHome ch)
        callHome = ch;
        seed = new Random();
        createDialog();
    public void showDialog()
        if(!dialog.isShowing())
            dialog.setVisible(true);
    private void createDialog()
        JButton change = new JButton("change background");
        change.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent e)
                callHome.setBackground(getColor());
                dialog.dispose();
        JPanel p = new JPanel();
        p.add(change);
        dialog = new JDialog();
        dialog.getContentPane().add(p);
        dialog.setSize(200,100);
        dialog.setLocation(525,200);
    private Color getColor()
        return new Color(seed.nextInt(0xffffff));
}

Error while usind Private Method of a global class

HI All..
I created a global class (ZLINE_GLOBAL) which has TOT_DATA private method. I have to call this private method in my report, I know that using Friend class we can do this.
But it is not working and showing the same error " METHOD "TOT_DATA" is unknown or Private or Public..
code i tried is
CLASS c2 DEFINITION DEFERRED.
CLASS ZLINE_GLOBAL DEFINITION FRIENDS c2.
PUBLIC SECTION.
    METHODS : m1.
PRIVATE SECTION.
    METHODS: m2.
ENDCLASS.
CLASS ZLINE_GLOBAL IMPLEMENTATION .
METHOD m1.
    WRITE : 'Public Method C1'.
ENDMETHOD.                    "M1
METHOD m2.
    WRITE : 'Private Method C1'.
ENDMETHOD.
ENDCLASS.
CLASS c2 DEFINITION FRIENDS ZLINE_GLOBAL. "my friends are here, allow them access to my (C2's) private components
PUBLIC SECTION.
    METHODS :m3.
ENDCLASS.
CLASS c2 IMPLEMENTATION.
METHOD m3.
    DATA : obj TYPE REF TO ZLINE_GLOBAL.
    CREATE OBJECT obj.
    CALL METHOD obj->TOT_DATA.    "here Iam calling Private method of global class
ENDMETHOD.                    "M3
ENDCLASS.
START-OF-SELECTION.
DATA obj_c2 TYPE REF TO c2.
CREATE OBJECT obj_c2.
obj_c2->m3( ).
can anybody help me on this..
Murthy

Hi Murthy,
Replace TOT_DATA with M2, you do not have any method by name "TOT_DATA" in your code.
CLASS c2 DEFINITION DEFERRED.
CLASS ZLINE_GLOBAL DEFINITION FRIENDS c2.
PUBLIC SECTION.
    METHODS : m1.
PRIVATE SECTION.
    METHODS: m2.
ENDCLASS.
CLASS ZLINE_GLOBAL IMPLEMENTATION .
METHOD m1.
    WRITE : 'Public Method C1'.
ENDMETHOD.                    "M1
METHOD m2.
    WRITE : 'Private Method C1'.
ENDMETHOD.
ENDCLASS.
CLASS c2 DEFINITION FRIENDS ZLINE_GLOBAL. "my friends are here, allow them access to my (C2's) private components
PUBLIC SECTION.
    METHODS :m3.
ENDCLASS.
CLASS c2 IMPLEMENTATION.
METHOD m3.
    DATA : obj TYPE REF TO ZLINE_GLOBAL.
    CREATE OBJECT obj.
    CALL METHOD obj->M2.    "here Iam calling Private method of global class
ENDMETHOD.                    "M3
ENDCLASS.
START-OF-SELECTION.
DATA obj_c2 TYPE REF TO c2.
CREATE OBJECT obj_c2.
obj_c2->m3( ).
Regards,
Chen

Why are all methods virtual???

class Base
     public Base()
          System.out.println("Calling f() from base class ...");
          f();
          return;
     public void f()
          System.out.println("Base class function called!");
          return;
class Derived extends Base
     public Derived()
          System.out.println("Calling f() from derived class ...");
          f();
          return;
     public void f()
          System.out.println("Derived class function called!");
          return;
     public static void main(String args[])
          new Derived();
          return;
}The problem in this: the call to f() from the Base class calls the Derived class method. I want it to call the Base class method. How do I do this?
Ravi

Sorry, I cant explain the circumstances under which I
encountered this problem without explaining a whole
lot about my product. But I cant make it a private
method because I need to be able to call it from
outside the package. I found a workaround for my
problem by putting a call to super.f() in the derived
class. But I really wonder why the makers of Java
chose to make it this way!
RaviIf you can't explain your problem then don't post your questions here. It's not like a small post on a forum board will cause your IP any damage.
The design of OOP is that if you override a method in a subclass of an object, the reason for doing so is that you are add/changing functionality of that method. If you don't need to add/change functionality of a method then don't override it. Polymorphism ensures that no matter what type of object the compiler thinks you are reffering to, at runtime you will call the correct method of the type of object you encounter then. This is why interfaces work. calling the super class to complete processing of a method is not a hack, or a design problem it's the way to do it. If the class that you are extending changes private data structures in a method, and you override that method, unless you are doing a radical change to the class, you probably need to call the super method to ensure that the proper changes are made.

Final method and final class

What is final method and final class in abap objects.

ejp wrote:
Since that doesn't work--or would overyy complex to implement... would be impossible to implement. Once the method-local copy goes out of existence, ipso facto it can never be changed. This is the whole point.I consider it impossible too, but I'm not a language/compiler/runtime expert, so I allowed for the possibility that there could be some way to do it--e.g. local variables that are references in inner classes live on the heap instead of the stack, or something. My point isn't that it's possible, just that if it were somehow to be done, it would by ugly, so we may as well consider it impossible--it just ain't gonna happen.
we go with the logic, "Okay, we need to copies, but keeping them in sync is a nightmareNo, it is +meaningless.+No, it's not meaningless. If we have the two copies, and they're not final, then after the inner object is created, the method can continue running, and either the method or the inner object could modify its copy. As far as our code knows, it's the same variable, so there'd have to be some way to keep them in sync. That's either impossible or undesirably complex--like the above, it doesn't matter which--so it's final in order to get past the issue of keeping the copies in sync.

I am opening a public access/community TV station soon. We are thinking of using Final Cut X for our staff

I am opening a public access/community TV station very soon. We are thinking of using Final Cut X for our staff and community producers. I am curious if there are any special discounts for multiple purchases of computers, but also for Final Cut X software? Does anyone reading have any experience from a public access TV perspective?

Hi SCaryPictures,
I run a PEG station, where I have used FCP7, AvidExpressPro, Adobe CS6/CC, and FCPX - I am approaching 2 years with my FCPX experience. I'd be happy to engage with you in a private email thread about my experience (I value my access to the people on this forum, and I don't want the Apple staffers to take offence.) Good luck founding your station!
Eric D - [email protected]
CoralVision (City of Coralville, IA)

Call Enterprise Bean (or Database) from private Method in Session-Bean

Hi Everybody,
I've a question regarding the possibility to call an dependency injected EJB in an private method of a session bean.
Imagine the following.
@Stateless
public class SomeBean implements SomeLocal{
   @EJB
   private AnotherLocal anotherBean;
   /** Will be called from a web-app via delegate layer */
   @TransactionAttribute(TransactionAttribute.RequiresNew)
   public void someBusisnessMethod(){
       String something = this.getSomeThing();
       //Do more
   private String getSomeThing(){
      return anotherBean.aMethodWhichCallsTheEntityManager();
}I've to refactor code with uses such Call-Hierachy and I want to know whether this is a correct way? Somebody told me that such stuff should not be made, and I quess he told me an explanation, why not to do such stuff, but unfortunally I've forgotten that. Do someone have a suggestion why not to do this? Could it blow the application to hell? Is there any difference to the following code (The way I would have done it)?
@Stateless
public class SomeBean implements SomeLocal{
   @EJB
   private AnotherLocal anotherBean;
    @Resource
    private SessionContext sessionContext;
   /** Will be called from a web-app via delegate layer */
   @TransactionAttribute(TransactionAttribute.RequiresNew)
   public void someBusisnessMethod(){
       SomeLocal self = this.sessionContext.getBusinessObject(SomeLocal.class);
       String something = self.getSomeThingBusinessMethod();
       //Do more
   @TransactionAttribute(TransactionAttribute.Required)
   public String getSomeThingBusinessMethod(){
      return anotherBean.aMethodWhichCallsTheEntityManager();
}

Found the answer by myself....
Here it is if someone might have the same question:
http://stackoverflow.com/questions/3381002 or if the link may down sometime the content of the answer...
>
The motivation here is that most EJB implementations work on proxies. You wouldn't be too far off in thinking of it as old-school AOP. The business interface is implemented by the EJB container, quite often via a simple java.lang.reflect.Proxy, and this object is handed to everyone in the system who asks for the ejb via @EJB or JNDI lookup.
The proxy is hooked up to the container and all calls on it go directly to the container who will preform security checks, start/stop/suspend transactions, invoke interceptors, etc. etc. and then finally delegate the call to the bean instance -- and of course do any clean up required due to any exceptions thrown -- then finally hand the return value over through the proxy to the caller.
Calling this.foo() directly, or passing 'this' to a caller so they can make direct calls as well, will skip all of that and the container will be effectively cut out of the picture. The 'getBusinessObject(Class)' method allows the bean instance to essentially get a proxy to itself so it can invoke its own methods and make use of the container management services associated with it -- interceptors, transaction management, security enforcement, etc.
written by David Blevins

Error in private methods when implementing a BAdI

Hi,
I implemented a BAdI and added some custom private methods in my implementing class. When I looked at the object list, my private methods are marked with a color red circular shape, which I guess it means those have error. But, when I tried to activate and test the BAdI, it works fine. Any idea why it marks my private methods as error? Am I missing something here?

it denotes Accessibility / Visibility of those methods .
regards
Prabhu

Help w/ private methods program..

hi guys...
i was just wondering if somebody can help me w/ the code i am writing for a project..
the project is about prime numbers and its factors.
-we have to create a private method called checkInput() which is sent the users String inputted number as a parameter and returns a boolean indicating wether the input is valid or not. (I am using inputNum as the variable that holds the number)
-also i have to call that checkInput private method from some other private method, which giving me errors when compiling...
thanks a lot...
private void getInput()throws IOException
BufferedReader stdin = new BufferedReader
(new InputStreamReader(System.in));
System.out.print("Enter an INTEGER number greater than "+MIN+". ");
while (inputNum <= 1)
System.out.print("Enter an INTEGER number greater than "+MIN+". ");
inputNum= Integer.parseInt(stdin.readLine());
}//end of while loop
checkInput();
}//end of method getInput.
// This method is to send the users String inputted
// number as a formal parameter and returns
// a boolean indicating whether the input is valid
// or not.
private boolean checkInput(String inputNum)
while(inputNum != null)
return true;
}///end of checkInput method.
// This method is to pass a formal parameter number
// which is a valid integer number that the user
// entered. The method will return a Boolean
// value indicating whether the number is a prime.
private boolean IsPrime (int number)
if (number == 1 || number == 2)
return true;
for (int i=2; i<(int)(number/2); i++)
if ( (number/i)==(int)(number/i) )
return false;
return true;
}//end of method IsPrime.
// This method calls the IsPrime method passing
// it the actual parameter inputNum which is
// valid user inputted number.
private void checkForPrime ()
IsPrime(inputNum);
if(true){
System.out.println(inputNum+ " is a prime");
}else
System.out.println(inputNum+ " is not a prime");
printAllFactors(inputNum);
}// end of checkForPrime method.
// This method prints out "Its factors are:",
// skips a line and then prints out all the factors
// of the formal parameter number.
private void printAllFactors (int number)
System.out.println("Its factors are: ");
System.out.println();
for (int i = 2; i <= number; i++){
if(inputNum % number == 0)
System.out.println(number + " is a factor.");
break;
System.out.println(number + " is not a factor.");
}// end of printAllFactors method.
}// end of main class.this is the code i have so far...

Please don't crosspost. It cuts down on the effectiveness of responses, leads to people wasting their time answering what others have already answered, makes for difficult discussion, and is generally just annoying and bad form.

Override a private method in a Base class?

How can a subclass override a final method in its superclass.
This code compiles cleanly.
How is this possible?
Or Am I overlooking any point?
class MySuperClass{
private final String getMessage(){
     return "hello";
protected String getAnotherMessage(){
     return getMessage() + "world";
class MySubClass extends MySuperClass{
private final String getMessage(){
     return "hi";
public String getAnotherMessage(){
   return "anothermessage";
}

getMessage is declared as private in the base class, and therefor cannot be overridden in any subclass.
Edit: I think I understand the question better now. You want to know why it compiles when you think it shouldn't. It's because the private method isn't really inherited at all. Your subclass created a brand new private method of the same signature, but it's completely unrelated.

Are private methods inherently final?

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