Super class for java Language

which is the super class for java Language...
this is an interview question .
I SAY Object is the super class for java Language ...
then he asked whether object class will extend ??
i say Yes it will implectly extend ...
then he whether each and every class will extend object
i say yes ...
then he asked multiple inheritance is possible in java ...
i say no ...
then how will say object class will extend in each and every class....
hai friends if there is any solution tell mem
by
dhana

which is the super class for java Language...
this is an interview question .
I SAY Object is the super class for java Language
ge ...If you mean the ultimate parent of all classes, yes.
(Although it's not the parent of interfaces.)
then he asked whether object class will extend ??
i say Yes it will implectly extend ...Not sure what is meant by "will object extend."
then he whether each and every class will extend
object
i say yes ...Correct.
then he asked multiple inheritance is possible in
java ...
i say no ...Correct. At least in the usual sense. When people talk about multiple inheritance, the usually mean multiple inheritance of implementation, such as C++ supports. The ability to implement more than one interface in Java is sometimes referred to as multiple inheritance of interface. I don't know if that term is in common use outside of Java.
then how will say object class will extend in each
and every class....
hai friends if there is any solution tell memMultiple inheritance means that a class' ancestors are not all in a straight line to the ultimate parent. That is, not all ancestors are parents or children of each other.
You are you father's son, and he is his father's son, and so on. So your grandfather is your ancestor, and so is your father. This is not MI.
You also have a mother. She's neither an ancestor nor a descendant of your father. That's MI.

Similar Messages

Why Object is a super class in java?

hi all i have got one basic doubt in java. why Object class is a super class in java. C++ is also a object oriented language but there there is no concept of making object as a super class, but in java why we are having that. thanks

Personally, I find the fact that C++ (and Delphi) DOES NOT have a common base class something of an inconvenience at times. The reason is that Java is an (almost) pure Object Oriented language, while C++ and Delphi are partially-object-oriented additions to C and Pascal respectively.
RObin

Super Class of Java

can any one tell what is the super class of JAVA?

How can u assume a to be = b and then prove that a = b based on the assumption that a=b... --:)
also 0 = 1 ....> which leaves Aryabhatta thinking why the Hell did I invented zero , when it will turn out to be 1 in future .:). no NOR gates required .. cool ... No boolean datatype required ....... rather no computer bo byte funda when 1 = 0 ..... Hurray so no Java ...... No Exceptions ..... So we would be only left with our old Crashproof Word Processor ( Commonly known as TypeWriter)

Does anyone know of any Sun Classes for Java Cryptographic Extension -JCE ?

Hello - anyone know of any Sun Classes for Java Cryptographic Extension? If so do you have the Sun class code/s?
Edited by: Mister_Schoenfelder on Apr 17, 2009 11:31 AM

Maybe this can be helpful?
com.someone.DESEncrypter
======================
package com.someone;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.KeySpec;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;
public class DESEncrypter {
    Cipher ecipher;
    Cipher dcipher;
    // 8-byte Salt
    byte[] salt = {
        (byte)0xA9, (byte)0x9B, (byte)0xC8, (byte)0x32,
        (byte)0x56, (byte)0x35, (byte)0xE3, (byte)0x03
    // Iteration count
    int iterationCount = 19;
    public DESEncrypter(String passPhrase) {
        try {
            // Create the key
            KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), salt, iterationCount);
            SecretKey key = SecretKeyFactory.getInstance(
                "PBEWithMD5AndDES").generateSecret(keySpec);
            ecipher = Cipher.getInstance(key.getAlgorithm());
            dcipher = Cipher.getInstance(key.getAlgorithm());
            // Prepare the parameter to the ciphers
            AlgorithmParameterSpec paramSpec = new PBEParameterSpec(salt, iterationCount);
            // Create the ciphers
            ecipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);
            dcipher.init(Cipher.DECRYPT_MODE, key, paramSpec);
        } catch (java.security.InvalidAlgorithmParameterException e) {
             e.printStackTrace();
        } catch (java.security.spec.InvalidKeySpecException e) {
             e.printStackTrace();
        } catch (javax.crypto.NoSuchPaddingException e) {
             e.printStackTrace();
        } catch (java.security.NoSuchAlgorithmException e) {
             e.printStackTrace();
        } catch (java.security.InvalidKeyException e) {
             e.printStackTrace();
    public DESEncrypter(SecretKey key) {
        try {
            ecipher = Cipher.getInstance("DES");
            dcipher = Cipher.getInstance("DES");
            ecipher.init(Cipher.ENCRYPT_MODE, key);
            dcipher.init(Cipher.DECRYPT_MODE, key);
        } catch (javax.crypto.NoSuchPaddingException e) {
             e.printStackTrace();
        } catch (java.security.NoSuchAlgorithmException e) {
             e.printStackTrace();
        } catch (java.security.InvalidKeyException e) {
             e.printStackTrace();
    public String encrypt(byte[] data) {
         return encrypt(new sun.misc.BASE64Encoder().encode(data), false);
    public byte[] decryptData(String s) throws IOException {
         String str = decrypt(s, false);
         return new sun.misc.BASE64Decoder().decodeBuffer(str);
    public String encrypt(String str, boolean useUTF8) {
        try {
            // Encode the string into bytes using utf-8
            byte[] utf8 = useUTF8 ? str.getBytes("UTF8") : str.getBytes();
            // Encrypt
            byte[] enc = ecipher.doFinal(utf8);
            // Encode bytes to base64 to get a string
            return new sun.misc.BASE64Encoder().encode(enc);
        } catch (javax.crypto.BadPaddingException e) {
             e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
             e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
             e.printStackTrace();
        } catch (java.io.IOException e) {
             e.printStackTrace();
        return null;
    public String decrypt(String str, boolean useUTF8) {
        try {
            // Decode base64 to get bytes
            byte[] dec = new sun.misc.BASE64Decoder().decodeBuffer(str);
            // Decrypt
            byte[] utf8 = dcipher.doFinal(dec);
            // Decode using utf-8
            return useUTF8 ? new String(utf8, "UTF8") : new String(utf8);
        } catch (javax.crypto.BadPaddingException e) {
             e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
             e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
             e.printStackTrace();
        } catch (java.io.IOException e) {
             e.printStackTrace();
        return null;
     // Here is an example that uses the class
     public static void main(String[] args) {
         try {
             // Generate a temporary key. In practice, you would save this key.
             // See also e464 Encrypting with DES Using a Pass Phrase.
             SecretKey key = KeyGenerator.getInstance("DES").generateKey();
             // Create encrypter/decrypter class
             DESEncrypter encrypter = new DESEncrypter(key);
             // Encrypt
             String encrypted = encrypter.encrypt("Don't tell anybody!", true);
             // Decrypt
             String decrypted = encrypter.decrypt(encrypted, true);
         } catch (Exception e) {
              e.printStackTrace();
          try {
              // Create encrypter/decrypter class
              DESEncrypter encrypter = new DESEncrypter("My Pass Phrase!");
              // Encrypt
              String encrypted = encrypter.encrypt("Don't tell anybody!", true);
              // Decrypt
              String decrypted = encrypter.decrypt(encrypted, true);
          } catch (Exception e) {
               e.printStackTrace();
}

Why how Abstract class   for java.util.set

I need to use Set i din't find any impelemnted class for Set, i don't want HashSet or LinkedHashSet just a Set is enough for my purpose.
How can i take instance of AbstractSet it is abstract.....
Is the only way is to write my own class extending AbstractSet.
Or is there something which i'm missing
TIA Nas

Because Vector isn't an ancsetor of AbstractList.
What you are trying to do is the same as saying that becasue my cousin and I have the same grandfather we must have the same parent which isn't true.
           Collection
        Set         List
   AbstractSet      AbstractList
   HashSet              Vector

Writing a documentation for Java-Language

Im learning Java with the tutorials here at sun.
Because my english is not best, I write down all "important" things in an own Dokumentation in german language.
Because there may be some code I write there, it would be useful to write the Documentation as *.java , because these code snipets are better to read then.
My question: Is there a possibility to write my documentation as *.html file , and the code snippets are same like I would write them in my JCreator-program (I mean, that keywords as int or class are written in blue, for example...) ?
Thanks in forward
Martin

You can use JavaDoc on your own code. To do this you would add comments in your code using the Javadoc comment style:
* This is JavaDoc
* Continue your comments here
* @author this is the author
* @param describe a paramater here
* @param describe another paramater here
* @return this line describes the return value
Then run the JavaDoc program on your code and it will produce the same kind of html that you see with the Java API html documentation. For more info check out the book Thinking In Java (available for free at www.bruceeckel.com )

QR Code/Datamatrix Generator Class for Java

Hi
i want to implement QR Code/Datamatrix in my Application.
Goolging for around 2 hours couldnt give me any results.
Is there a class, api, library, that could help me generating Images out of strings?
Nam

"i want to implement QR Code/Datamatrix in my Application."
Then just pick one of the libraries, I rand across literally a dozen while I was looking for that how to implementation for you to code.
Please note for future use--implement has specific meaning to programmers--usually having a do it yourself connotation--as in: I want to build my own package to do this.

Seeking recommendations for Java and servlet tutorials

I am newbies in Java, except knowing some JavaScripts, JSP for web programming. Currently, I am using PHP, MySQL, Apache, and now I would like extend my skills to Java.
I visited the java website, it seems to have many different packages and tech for different requirement. What should I learn for web programming? And which database is mostly fit for Java language? Mysql? oracle?

If you want to do web programming, JSP and JavaScript is a good start. You'll also need to know servlets. Since you are new to Java, you'll also need to learn some of the basic classes. I would start with Sun's Java tutorial and when you have mastered that move on to their J2EE tutorial and focus on the chapters that deal with servlets, jsps and related technologies. The J2EE tutorial will include other topics that you may not want to learn right now.
All major relational databases can be used with Java. The JDBC api can be used for all of them. There might be some minor differences in how you code you queries but the way you do things is the same regardless of the database.

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.

XMLEncoder usage for Java to XML Serialization

I have recently started using XMLEncoder and XMLDecoder to perform Java Bean to XML Serialization and Deserialization. It seems to break when multiple threads are using XMLEncoder, even if each Thread is using a separate instance of XMLEncoder. I was initially seeing NullPointer exception and after obtaining a fix for that IBM Support, we are seeing various other exceptions like this.
java.lang.IllegalAccessException: Can not call newInstance() on the Class for java.lang.Class
java.lang.Exception: discarding statement XMLEncoder0.writeObject(TestObject0);
java.lang.Exception: discarding statement XMLEncoder0.writeObject(TestObject0);
     at java.beans.XMLEncoder.writeStatement(XMLEncoder.java:352)
     at java.beans.XMLEncoder.writeObject(XMLEncoder.java:266)
     at test.XMLEncoderIssue.run(XMLEncoderIssue.java:59)
     at java.lang.Thread.run(Thread.java:570)
Caused by: java.lang.RuntimeException: failed to evaluate: <unbound>=Class.new();
java.lang.ArrayIndexOutOfBoundsException: 0
at java.beans.ObjectHandler.dequeueResult(XMLDecoder.java:285)
at java.beans.XMLDecoder.readObject(XMLDecoder.java:163)
at test.XMLEncoderIssue.run(XMLEncoderIssue.java:75)
at java.lang.Thread.run(Thread.java:570)
What am i missing here?

Just add an empty constructor in your class

Regarding Super classes

Hi,
I have created one class in SE24. This class will be used as a super class for other classes.
When subclasses are derived from this superclass, i want to make sure that some of the methods of superclasses are redefined by the subclasse compulsarily.
So i want to force the subclasses to redefine complusarily some of the methods of its super class.
Is this feasible. If so please let me know the corresponding approach.
Thanks in advance !
Pramod

Hi,
Check this out this will help you.
Inheritance is the concept of passing the behavior of a class to another class.
1.You can use an existing class to derive a new class.
2.Derived class inherits the data and methods of a super class.
3.However they can overwrite the methods existing methods and also add new once.
4.Inheritance is to inherit the attributes and methods from a parent class.
Inheritance:
Inheritance is the process by which object of one class acquire the properties of another class.
Advantage of this property is reusability.
This means we can add additional features to an existing class with out modifying it.
Go to SE38.
Provide the program name.
Provide the properties.
Save it.
Provide the logic for inheritance.
*& Report ZLOCALCLASS_VARIABLES                      *
*&----------------------------------------------------*REPORT ZLOCALCLASS_VARIABLES.
*OOPS INHERITANCE
*SUPER CLASS FUNCTIONALITY
*DEFINE THE CLASS.
CLASS CL_LC DEFINITION.
PUBLIC SECTION.
DATA: A TYPE I,
      B TYPE I,
      C TYPE I.
METHODS: DISPLAY,
         MM1.
CLASS-METHODS: MM2.
ENDCLASS.
*CLASS IMPLEMENTATION
CLASS CL_LC IMPLEMENTATION.
METHOD DISPLAY.
WRITE:/ 'THIS IS SUPER CLASS' COLOR 7.
ENDMETHOD.
METHOD MM1.
WRITE:/ 'THIS IS MM1 METHOD IN SUPER CLASS'.
ENDMETHOD.
METHOD MM2.
WRITE:/ 'THIS IS THE STATIC METHOD' COLOR 2.
WRITE:/ 'THIS IS MM2 METHOD IN SUPER CLASS' COLOR 2.
ENDMETHOD.
ENDCLASS.
*SUB CLASS FUNCTIONALITY
*CREATE THE CLASS.
*INHERITING THE SUPER CLASS.
CLASS CL_SUB DEFINITION INHERITING FROM CL_LC. "HOW WE CAN INHERIT
PUBLIC SECTION.
DATA: A1 TYPE I,
      B1 TYPE I,
      C1 TYPE I.
METHODS: DISPLAY REDEFINITION,     "REDEFINE THE SUPER CLASS METHOD
         SUB.
ENDCLASS.
*CLASS IMPLEMENTATION.
CLASS CL_SUB IMPLEMENTATION.
METHOD DISPLAY.
WRITE:/ 'THIS IS THE SUB CLASS OVERWRITE METHOD' COLOR 3.
ENDMETHOD.
METHOD SUB.
WRITE:/ 'THIS IS THE SUB CLASS METHOD' COLOR 3.
ENDMETHOD.
ENDCLASS.
*CREATE THE OBJECT FOR SUB CLASS.
DATA: OBJ TYPE REF TO CL_SUB.
START-OF-SELECTION.
CREATE OBJECT OBJ.
CALL METHOD OBJ->DISPLAY. "THIS IS SUB CLASS METHOD
CALL METHOD OBJ->SUB.
WRITE:/'THIS IS THE SUPER CLASS METHODS CALLED BY THE SUB CLASS OBJECT'COLOR 5.
SKIP 1.
CALL METHOD OBJ->MM1.     "THIS IS SUPER CLASS METHOD
CALL METHOD OBJ->MM2.
*CREATE THE OBJECT FOR SUPER CLASS.
DATA: OBJ1 TYPE REF TO CL_LC.
START-OF-SELECTION.
CREATE OBJECT OBJ1.
SKIP 3.
WRITE:/ 'WE CAN CALL ONLY SUPER CLASS METHODS BY USING SUPER CLASS OBJECT' COLOR 5.
CALL METHOD OBJ1->DISPLAY. "THIS IS SUPER CLASS METHOD
CALL METHOD OBJ1->MM1.
CALL METHOD OBJ1->MM2.
This example will help you to solve your problem.
For more detailed information GOTO -> SAPTECHNICAL ->Tutorials -> Object Oriented Programming.
Regards Madhu.
Code Formatted by: Alvaro Tejada Galindo on Jan 7, 2009 12:13 PM

How to Change the default format for differnt language both in java and SQL

Hello,
I am using SQL Anywhere in my application.And in my java client application user can log in with their preferred language like English,French,German,Chinese,etc....When even the user log in to the application the data from the database will be displayed with respective to the language.But when i tried to see the dates in Interactive SQL all the dates r in the format of '2008-12-5 16:44:10:673' but say for example for Chinese it will be displayed as '08-12-5 16.44.10' and for some other language it will come in some other format(which is standard format for those language).
Mean while i am using java client.When ever i am displaying a date it will be with respective to the language using Locale and date format classes.When i am displaying the date for Chinese in GUI it will show the date as '08-12-5 下午4:44'. In summary
1. For Chinese,the default date pattern from SQL Anywhere date base is '08-12-5 16.44.10'
2. For the same language date using java code is displaying as '08-12-5 下午4:44'. and i am getting the time format pattern as 'ah:mm'.I tried to change the display format in regional settings but no change in display.
Is there any way to make both the time format as same?
Please help me to solve this issue!!!
Thanks in Advance!
Arun

pon_arun wrote:
Hello masijade,
I did as u said but still the date display is not the same......And I'm telling you that it doesn't matter. What "format" the DB likes to display a Date in when it displays it, is completely irrelevant to how you display it in your GUI.
A Date does not have a format. A String representation of a Date does.
As long as you use getDate from ResultSet and setDate from PreparedStatement you do not have to worry about this. Those methods will handle dates to and from the DB themselves. You can then use SimpleDateFormat to display the Date anyway you want to.
Just because you show the Date one way, and the DB shows it another, does not mean that it is not the same date. Don't get hung up on how the String representation of the Date looks.
Edit: If you simply want to be able to do "Human Comparisons" then look at the SQL TO_CHAR function (for Oracle, for other DBs the function name may vary). And for Java, read the API docs for SimpleDateFormat (as already intimated above).

{@inheritDoc} not working for Java Classes

Hello,
i am using {@inheritDoc} for inherting super class's JavaDoc for a perticular function..
It is working, if super class is my own class. i am able to see all JavaDoc in child class.
But when i use {@inheritDoc} for extending JavaDoc of java class it is not working.
i.e. if i am writing {@inheritDoc} in public void actionPerformed(ActionEvent e) method..
It wont show any javadoc..
How to add it? Do i need to give source of java classes too???
And if it is Yes, then where to specifiy. and where to find source of Java classes, do they come with JDK? or NetBeans?? (If yes then where it is in JDK or Netbeans???)
Thanks,
Nachiket.

Yes, you need to have the Java source, with the -sourcepath option, as described here:
Inheriting Comments from J2SE - Your code can also automatically inherit comments from interfaces and classes in the J2SE. You can do this by unzipping the src.zip file that ships with the SDK (it does not contain all source files, however), and add its path to -sourcepath. When javadoc runs on your code, it will load the doc comments from those source files as needed. For example, if a class in your code implements java.lang.Comparable, the compareTo(Object) method you implement will inherit the doc comment from java.lang.Comparable.
http://java.sun.com/j2se/javadoc/faq/#incrementalbuild
If you want the full Java source get it from here:
http://www.sun.com/software/communitysource/j2se/java2/index.xml
http://java.sun.com/j2se/javadoc/faq/#sourcecode
-Doug

Is there Java support for Indian languages other than Hindi?

I'd like to use Tamil as a test language for some translated java files.
I don't know whether it is supported or not.
Alternatives are Bangla, Gujararati, Kannada, Marathi, Oriya, Punjabi, Telugu. Are any of these supported?
I'd prefer not to use Hindi.
The only website I can find listing the languages supported is from 2003. If you have a link to a more recent one, I would appreciate it.

Locale is basically a glorified String[], so the idea that some locales are supported and others are not is sort of illusory.
Quoting from the API...
[quote begins]
Locale(String language, String country, String variant)
The language argument is a valid ISO Language Code. These codes are the lower-case, two-letter codes as defined by ISO-639... The country argument is a valid ISO Country Code. These codes are the upper-case, two-letter codes as defined by ISO-3166...
Because a Locale object is just an identifier for a region, no validity check is performed when you construct a Locale...
The Locale class provides a number of convenient constants that you can use to create Locale objects for commonly used locales...
A Locale is the mechanism for identifying the kind of object (NumberFormat) that you would like to get. The locale is just a mechanism for identifying objects, not a container for the objects themselves.
[quote ends]
In other words, if you wanted to make up your own local for the language that they speak on Planet X (Xian), you could perfectly well have a Local object for that and properties or list files for it.
Drake

PersistentProxy class usage for 3rd party super class

Hi,
I am using PersistentProxy class for 3^rd^ party super class. Please see code below for proxy class.
@Persistent(proxyFor=AIAMessageHeader.*class*)
public class AIAMessageHeaderProxy implements PersistentProxy<AIAMessageHeader>{
public AIAMessageHeader convertProxy() {
AIAMessageHeader h = null;
//some code here
return h;
public void initializeProxy(AIAMessageHeader h) {
//some code here
I am not sure how to register this proxy class using EntityModel:registerClass method before opening EntityStore. Before opening store, entity model object is null. I tried creating object of AnnotationModel and register class, set back it using setModel method of StoreConfig. But no help!!
Can someone put code snippet to do that? Without registration, it throws following exception.
Exception in thread "main" java.lang.IllegalArgumentException: Persistent class has non-persistent superclass:

Thanks so much charles for replying me.
I tried the steps as you mentioned but did not work. It's still throwing exception. Please see code below.
public class TestData extends AIAMessageHeader {
     @PrimaryKey
     String testStr;
     public static void main(String[] args) {
          new TestData().start();
     public void start (){
          try {
               EnvironmentConfig envConfig = new EnvironmentConfig();
               StoreConfig storeConfig = new StoreConfig();
               // Allow environment and store to be created if does not exist
               envConfig.setAllowCreate(true);
               storeConfig.setAllowCreate(true);
               // set for AutoCommit of transaction
               envConfig.setTransactional(true);
               storeConfig.setTransactional(true);
               AnnotationModel model = new AnnotationModel();
               model.registerClass(com.jpm.equities.aia.cache.AIAMessageHeaderProxy.class);
               storeConfig.setModel(model);
               // open environment and EntityStore (database for caching data)
               Environment env = new Environment(new File(
                         "C:\\workspace\\RollingIOIServer\\dbenv"), envConfig);
               EntityStore s = new EntityStore(env, "EntityStore", storeConfig);
               PrimaryIndex<String, TestData> pi = null;
               pi = s.getPrimaryIndex(String.class, TestData.class);
               TestData td = new TestData();
               td.setTestStr("Kinnari");
                              pi.put(td);
               System.out.println("inserted object into cache");
               TestData t = pi.get("Kinnari");
               System.out.println("found data " + t.getTestStr());
          } catch (Exception e) {
               AIALogger.getAIALogger().fatal("Exception : ", e);
Thanks in advance!!
Kinnari

Super class for java Language

Similar Messages

Maybe you are looking for