Super class of all Classes

Can any one tell me a class name which is not inherited from Object as we know that all class inherited from Object class.

Class Evaluator; I've written it myself and it definitely doesn't extend
the Object class because I implemented it using C++. Satisfied?
kind regards,
Jos

Similar Messages

Calling a particular Method of all subclass from a super class

hi
I have a class 'A' which is a super class for 'B' ,'C' , 'D'
my main method is in the class Main and while on the run i am calling methods of B,C,D form this main class.
but as the first step of execution i need to call a init method which has been defined in all the sub-classes. and there can be any no of sub-classes and all will have the init method and i have to call the init method for all classes. is this possible to do that in runtime. ie i wil not be knowing the names of sub-classes.
thanks
zeta

Sorry if i had mislead you all.
I am not instantiating from my super class.
as mjparme i wanted one controller class to do the
init method calls
so i got it working from the link you gave.
URL url = Launcher.class.getResource(name);
File directory = new File(url.getFile());
This way i can get all the classes in that
in that package
and from reflection i can get whether it is
her it is a sub class of the particular super class
and i can call the init methods by making the init
methods static
thanks for the help
zetaThis is a rather fragile solution.
If the problem is one of knowing which subclasses exist, I would suggest specifying them explicitly via configuration (system property or properties file or whatever).
One thing that's not entirely clear to me: Is the init going to be called once for each subclass, or once for each instance of each subclass? It sounds to me like it's once per class, but I want to make sure.

How to inherit super class constructor in the sub class

I have a class A and class B
Class B extends Class A {
// if i use super i can access the super classs variables and methods
// But how to inherit super class constructor
}

You cannot inherit constructors. You need to define all the ones you need in the subclass. You can then call the corresponding superclass constructor. e.g
public B() {
super();
public B(String name) {
super(name);
}

Calling a method from a super class

Hello, I'm trying to write a program that will call a method from a super class. This program is the test program, so should i include extends in the class declaration? Also, what code is needed for the call? Just to make things clear the program includes three different types of object classes and one abstract superclass and the test program which is what im having problems with. I try to use the test program to calculate somthing for each of them using the abstract method in the superclass, but its overridden for each of the three object classes. Now to call this function what syntax should I include? the function returns a double. Thanks.

Well, this sort of depends on how the methods are overridden.
public class SuperFoo {
public void foo() {
     //do something;
public void bar(){
     //do something
public class SubFoo extends SuperFoo {
   public void foo() {
      //do something different that overrides foo()
   public void baz() {
      bar(); //calls superclass method
      foo(); //calls method in this (sub) class
      super.foo(); //calls method in superclass
}However, if you have a superclass with an abstract method, then all the subclasses implement that same method with a relevant implementation. Since the parent method is abstract, you can't make a call to it (it contains no implementation, right?).

Calling the super class method from the subclass

Hi all,
I have a question about inheritence and redefinition of methods. Is it possible to call the superclass implementation of a method which is redefined in the subclass in another method of the subclass?There are possbilities like creation of an explicit super class instance or delegating the super class method implementation to another method which is also protected etc. What i mean is, is there a direct way of calling it?We have ,me, as the reference for the instance we have(which is the subclass instance in this case), is there also a way of pointing the superclass implementation(with super we can reference in the subclass redefinition, my question is if we have such a parameter in other methods of the subclass too)
Thanks in advance
Sukru

Hi,
The super reference can only be used in redefined methods to call superclass implementation . So probably what you can do is use upcasting and access the required superclass implementation. I can think of only this way...;-)
Ex data lr_super type ref to cl_superclass
lr_super = lr_subclass.
lr_super->method().
~Piyush Patil

Trying to use super class's methods from an anonymous inner class

Hi all,
I have one class with some methods, and a second class which inherits from the first. The second class contains a method which starts up a thread, which is an anonymous inner class. Inside this inner class, I want to call a method from my first class. How can I do this?
If I just call the method, it will use the second class's version of the method. However, if I use "super," it will try to find that method in the Thread class (it's own super class) and complain.
Any suggestions?
Code:
public class TopClass
     public void doSomething(){
          // do something
=============================
public class LowerClass extends TopClass
     // overrides TopClass's doSomething.
     public void doSomething(){
          // do something
     public void testThread(){
          Thread t = new Thread(){
               public void run(){
                    doSomething();               //fine
                    super.doSomething();          //WRONG: searches class Thread for doSomething...
          t.start();
}

Classes frequently call the un-overridden versions of methods from their superclasses. That's that the super keyword is for, if I'm not mistaken.You're not mistaken about the keyword, but you're not calling the superclass method from a subclass. Your anonymous inner class is not a subtype of TopLevel. It's a subtype of Thread.
Here it is no different, except that I happen to be in a thread at the time.It's vastly different, since you're attempting to call the method from an unrelated class; i.e., Thread.
I could also be in a button's action listener, for example. It seems natural to me that if I can do it in a method, I should be able to do it within an anonymous inner class which is inside a method.If you were in an button's action listener and needed to call a superclass' implementation of a method overridden in the button, I'd have the same questions about your design. It seems smelly to me.
~

Accessing a Sub class variable in a Super Class

Hi ,
Is there any easiest way to access a Subclass Variable in a Super Class.
Class Super1{
Class sub extends Super1
private String substring1;
In my application the 'substring1' values is not null .But all fields in Super1 class are null .
How can i access the value of the Subclass Variable in Super class .
Thanks

This would be a way to make the superclass dependent on subclass behavior. Of course this only makes sense if getSubString() is likely to have multiple different implementations in different subclasses.
public abstract class Super {
public String getString() {
   return "SuperString" + getSubString();
protected abstract String getSubString();
public class Sub extends Super {
private String substring;
protected String getSubString() {
   return substring;
}Using this just to access a variable whose contents differ from subclass to subclass is overkill. If you want each subclass to provide a different substring, create a constructor with a substring parameter in the superclass instead:public class Super {
private String substring;
protected Super(String substring) {
   this.substring = substring;
public String getString() {
   return "SuperString" + substring;
public class Sub extends Super {
public Sub() {
   super("substring");
}

Generic interface in abstract super class

hello java folks!
i have a weird problem with a generics implementation of an interface which is implemented in an abstract class.
if i extend from this abstract class and try to override the method i get this compiler error:
cannot directly invoke abstract method...
but in my abstract super class this method is not implemented as abstract!
do i have an error in my understanding how to work with generics or is this a bug in javac?
(note: the message is trown by the eclipse ide, but i think it has someting to do with javac...)
thanks for every hint!
greetings daniel
examples:
public interface MyInterface <T extends Object> {
   public String testMe(T t);
public abstract class AbstractSuperClass<T extends AbstractSuperClass> implements MyInterface<T> {
   public String testMe(T o) {
      // do something with o...
      // now we have a String str
      return str;
public final class SubClass extends AbstractSuperClass<SubClass> {
   @Override
   public String testMe(SubClass o)
      return super.testMe(o);
}

Hi Wachtda,
Firstly, T extends Object is redundant as all classes implicitly extend the Object class.
Therefore :
public interface MyInterface <T> {
   public String testMe(T t);
}Secondly, abstract classes may have both abstract and non-abstract instance methods. Also, two methods, one abstract and one non-abstract, must have a different signature.
The following example will give a compile error because the methods share the same signature :
abstract class Test {
     public void sayHello() {
          System.out.println("Hello");
     abstract public void sayHello();
}Therefore, to make an interface method as abstract would simply block the possibility of implementing it.
BTW, you can do this :
abstract class Test {
     public void sayHello() {
          System.out.println("Hello");
     abstract public void sayHello(String name);
}Finally, there's no bug in javac.

Problem of super class.

Hi all,
I am adding a menuItem to a menu of a menuBar which the menu has a old menuItem. The
requirement is that the old menuItem of the menu only enable in the main window and disable in the others, and the new menuItem only disable in the main window and enable in the others. The problem is that this menu class is a super class, the main class extends from it which coordinate all the other panels(windows). So when I try to enable the new menuItem in the others windows, I modified the super class, then it enable in the main window as well which is wrong. I don't allowed to modify the basic structure of the project.
Any ideas? Thanks a lot!

Please help!

Is there any way to access an overridden method of super class?

class Animals
void makeNoice(){System.out.println("General noice");}
class Dog extends Animals
void makeNoice(){System.out.println("bark");}
};Is there any way to access the makeNoice() of Animals class from a Dog object
Dog dog = new Dog();
Animal animaldog = dog;
animaldog.makeNoice(); // will always calls Dog's makeNoice() ie the overriden method.
Is there a way to access the Animals makeNoice() method ? by using cast or super etc?
Or it is not possible at all?

Rajeebs wrote:
Now another question coming in my mind.
Whether any way to access a method which belong to super class's super class without using any method of class B,
like super.super.fn() ??Isn't this just the same question again? And won't you again just "solve" it by writing some invokeSuperSuperMethod or other? This flawed design is quickly getting out of hand, isn't it? The question isn't "How can I invoke an arbitrarily deep superclass' method?" but more "Why do I need to invoke a method belonging to a concrete type at all?". If you need to do that, chances are you've misused inheritance.
To use your initial sample code, in what circumstance would you require that a Dog make anything other than a Dog noise? It makes no sense. Point is, you have an Animal abstraction, and can call makeNoise on any instance of any subclass, and it will make the appropriate noise. By trying to use trickery to force other noises, you're doing something unnatural, and you're also depending on actual specific concrete subclasses. If you're going to go to specific classes and ask them to make their noise, what use is the inheritance? What use it the polymorphism?
Are we heading into another "I've got a brilliant idea for a [useless language feature|http://forums.sun.com/thread.jspa?threadID=5423706&messageID=10905772#10905772], guys!" thread?

Javah problem - super class could not be found !!

Hi all,
i have already posted this message but i didn't get enough help to solve my poor situation.
and this is my problem:
i got in my project (myProject) MyClass class.
i wrote in another java class ,in OtherClass.class ,jni function that use MyClass object as parameter to the jni interface, as follow:
private native int myFunction (MyClass obj); //function in OtherClass
when i write the javah command line :
javah -jni OtherClass (in order to create OtherClass.h)
i always get the following error:
A required super class myPackage.MyClass could not be found.
my qoustion is how can i let the javah command line to know about the existence of myPackage.MyClass and how can i create and .h file when i using other class instance as jni function parameter in other class??
Thanks Sendy.

Lets define a few terms here.
Java can be a java virtual machine which is what runs when you type 'java' on the command line. It is also represented by the compiler which runs when you type 'javac'. And in your case it also is represented by 'javah'.
The class path defines where java finds classes that it needs.
In older versions of java you had to tell it where to find everything. It couldn't even find java.lang.String unless you told it were it was. Now days you have to tell it where to find stuff that you add (or where 3rd party libraries are.)
There are two ways to define the class path: a command line option and an environment variable.
A class path can, currently, have three types of things in it:
-A path to a zip file
-A path to a jar file
-A path
For example
-Path to zip file in windows: C:\mystuff\mylib\mystuff.zip
-Path to zip file in unix: /opt/system/projects/mystuff/mystuff.zip
-Path to jar file in windows: C:\mystuff\mylib\myjar.jar
-Path to jar file in unix: /opt/system/projects/mystuff/myjar.jar
-Path in windows: C:\mystuff\mylib
-Path in unix: /opt/system/projects/mystuff
Zip files aren't used as much anymore, but you should at least be aware of them.
Java uses the class path to look for classes which are stored in files. It does this by translating the class name into a file name. It uses packages as directory names and class names as file names. So in your case it would try to find a class called myPackage.MyClass in a file called myPackage\MyClass.class. It would try to find that in any zip files, jar files, in in any paths that you specified in the class path.
So java is trying to find myPackage\MyClass.class in your class path. It would try to find that in any zip files, jar files, in in any paths that you specified in the class path.
Right now your class path is probably just "." which means that if you do the following commands
cd C:\mystuff
javah -jni OtherClass
Then java is going to try to find myPackage.MyClass in the following file
.\myPackage\MyClass.class
That, because you 'cd' to C:\mystuff, translates to the following absolute path
C:\mystuff\myPackage\MyClass.class
So if java doesn't find that file then it is going to tell you that it can't find the file.
So where is your file? Let's say it is here.
C:\work\lib\myPackage\MyClass.class
So you must tell javah where the root is. Keep in mind that 'myPackage' must be part of the path. That is not optional. The root is the directory above 'myPackage'. So the root is
C:\work\lib
So now you have a path that is ready for your class path. So your javah command could look like this
javah -classpath ".;C:\work\lib" -jni OtherClass
Or using an environment variable
set CLASSPATH=.;C:\work\lib
javah -jni OtherClass
Keep in mind in the above that class path is a generic term and there can be other ways to define it. For example the Sun command "java" allows you to use "-classpath" or "-cp".
So does the above help?

Private or Protected access for super class variables

What is the best practice...
Assume there is a class hierachy like
Person (Super class) / StaffMember/ Professor (Sub class)
1) The best way is to keep all the instance variables of each and every class private and access the private variables of super classes through subclass constructors (calling "super()")
Ex:-
public class Person {
private String empNo;
public Person (String empNo) {
this.empNo = empNo;
public class Professor extends Person {
private String ........;
private int ...........;
public Professor (String pEmpNo) {
super(pEmpNo);
OR
2)Changing the access level of the super class variables into "protected" or "default" and access them directly within the sub classes...
Ex:-
public class Person {
protected String empNo;
public Person () {
public class Professor extends Person {
String ........;
int ...........;
public Professor (String empNo) {
this.empNo = empNo;
Thank you...

i'd think that you'd be better off relaying your initial values through the super class's constructor that way you'll get cleaner code, there's a possibly of inconsistency with option 2. i.e. you can then write code in your super classes to generally handle and properly initialize the instance variables while in the case of option 2, you'll have arbitrary constructors performing arbitrary initialization procedures

Nor any of its super class is known to this context ...problem

hi all
i have simple complex object in jave that looks like this :
@XmlAccessorType(XmlAccessType.FIELD)
public class MyID{
    @XmlAttribute
    public short dbnum = (short)0;
    @XmlAttribute
    public short usernum= (short)0;
    @XmlAttribute
    public long userid = (long)0;
    public MyId(){
}i converted it with jaxb and it generete me corespanding java object with the propreate geters and seters
now when i try to in the server side to insert this object into List<Object> im geting error saing :
Caused by: javax.xml.bind.JAXBException: com.WebServices.datastructures.MyID nor any of its super class is known to this context
at com.sun.xml.bind.v2.runtime.JAXBContextImpl.getBeanInfo(JAXBContextImpl.java:474)
at com.sun.xml.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:557)
... 47 more
i must say that if i send back only this object (MyID) the unmarsheling passed successfully
thanks for your help

Ok I found it out
jboss was using the jre default axis impelmentation while the server where my client was deployed was using the axis 2 implementation
I changed the server to use jre default axis and things worked now
Thanks
Sapan

Is it possible to OVERLOAD a super-class method in a sub-class?

Hi all,
I have a query that
Is it possible to OVERLOAD a super-class method in a sub-class?
If it is possible, please give me an example.
Thanks,
Hari

Hi,
Is the method int Display(int a){} overloading
the super-class's void Display() method? If
possible, please clarify this and how it would be
method overloading?
hanks,
Hari
Hi Hari,
Yes, it is possible. Look at this piece of code:
class Senior
     void Display()
          System.out.println("Super class method");
class Junior extends Senior
     int Display(int a)
          System.out.println("Subclass method: "+a);
          return(a+10);
     }> }
class example
     public static void main(String args[])
          Junior j = new Junior();
          j.Display();
System.out.println("Subclass method
od "+j.Display(5));
Is this what you were asking? Hope this helped.Hi,
I guess you guys are confused here...
Overloading is achieved by methods in the same class...
Overriding is across a superclass subclass methds.

Inherit protected attribute from a Super class

Hi All,
I am inheriting a standard class which has many instance protected attributes. how do i access the super classes protected attributes from the sub class. i.e i need the value present in the super class attribute to be used in a sub class method.
will i be able to get the value of an instance attribute??
Thanks in advance,
Arun.

Hi marc,
I was also wondering as to how we can make use of the public attributes in the sub classes.as in, what the syntax we need to follow.
It'd be great if you could give a simple example with one protecetd attribute accessed in the subclass.
I've written a sample prog.
REPORT YA_TEST_OO.
      CLASS s_abc DEFINITION
CLASS s_abc DEFINITION.
PRIVATE SECTION.
    DATA: d_abc TYPE i.
ENDCLASS.                    "s_abc DEFINITION
      CLASS sb_abc DEFINITION
CLASS sb_abc DEFINITION INHERITING FROM s_abc.
public SECTION.
DATA: sb_d_abc TYPE c." VALUE d_abc.
    METHODS: m_abc.
ENDCLASS.                    "sb_abc DEFINITION
      CLASS sb_abc IMPLEMENTATION
CLASS sb_abc IMPLEMENTATION.
METHOD m_abc.
   sb_d_abc = d_abc + 1.
ENDMETHOD.                    "m_abc
ENDCLASS.                    "sb_abc IMPLEMENTATION
It doesn't work though.
Thanx,
Zid.

Overiding super class method to an abstract method

public class Super
public void doSomethingUseful()
public abstract class Sub extends Super
public abstract void doSomethingUseful();
What is the OO principle behind this?
When do we need to override a super class method in subclass as an abstract?

Lets first look at a simple design pattern called "Template Method".
public abstract class Library
private void collectBooks()
// collect books here
private void putBookInShelf()
// put books in shelf here
// abstract method sortBooks()
public abstract void sortBooks();
public void processBooks()
collectBooks();
sortBooks();
putBooksInShelf();
this class is an abstract class giving an abstract method called "sortBooks()", what is it useful for? We can make a subclass and implement sortBooks() to sort the books as we want (title wise, author wise, date wise, publisher wise) and then simply call processBooks() to process them.
One Sub class may look like:
public class MyLibrary extends Library
public void sortBooks()
// sort books by title b/c I like them sorted out by title
Another sub-class may look like
public class HisLibrary extends Library
public void sortBooks()
// sort books by Author, b/c he likes his books sorted out by author
Now client will say:
public static void main(String str[])
MyLibrary mylib=new MyLibrary();
mylib.processBooks(); // books will be processed by sorting them title wise
HisLibrary hislib=new HisLibrary();
hislib.processBooks(); // books will be processed by sorting them author wise
So in Library class, method "sortBooks()" was a template method allowing subclasses to sort the books as they want while all other functionality was implemented by Library class itself.
Now if we go back to your example, a method which is concrete in super class that you converted into an abstract method in sub class ( doSomethingUseful() ) is now a template method, which alows the sub classes of this subclass to do something useful what they think is useful or in other words you are allowing subclasses of this subclass to implement this template method as they want by using their own algorithm.
Now why whould you do that? answer is that you don't have access to the code of super class, otherwise you must have made this method abstract in super class in the first place.
Note that the code may not compile, I tried to come up with an exmple and did not pay attention to compiler demands.
I think I cleared my point, It was tough to explain though.
Good Luck.
Khawar.

Super class of all Classes

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