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

Similar Messages

Puzzled by the redefinition of the methods in java.util.Set

Hi all,
I don't understand why those methods in java.util.Set redefined since their counterparts have alrealdy been defined in java.util.Collection and java.util.Set extends java.util.Collection. I agree to redefine boolean add(Object o) because its contract has been modified, but what about the rest like
size() and iterator() ?
Thanks.

Hi all,
I don't understand why those methods in
in java.util.Set redefined since their counterparts
have alrealdy been defined in java.util.Collection
and java.util.Set extends java.util.Collection. I
agree to redefine boolean add(Object o) because its
contract has been modified, but what about the rest
like
size() and iterator() ?Completeness's sake?
~Cheers

Why interfaces why not abstract classes?

why they are using interfaces concept in JDBC or struts2.0 why not abstract classes?
thanks in advance.

user5287726 wrote:
jverd wrote:
user5287726 wrote:
Interfaces are more flexible. For certain definitions of flexible, yes, but not for others.
A Java class can only inherit one class, but it can implement multiple interfaces.Which has absolutely nothing to do with why JDBC declares interfaces rather than abstract classes.How does your post even attempt to answer the OP's question?OP asked: "why they are using interfaces concept in JDBC or struts2.0 why not abstract classes?" I'm pointing out that your post does not address the question asked. And of course your answer is wrong anyway.
As for addressing the OP's question, I did that in my first response.

ADF Faces af:table support java.util.Set

I was using a java.util.Set in my model classes, as implementation of the Collection interface. And wanted to show the Set using a <af:table> after a while I discoverded that the documentation did not mention support of java.util.Set, only List.
Now I have to convert my collection to List in the backing beans of my view.
Is there a better approch than converting every Set in the view using
new Arraylist(set)?
And what is the reason of the missing Set support (or General Colelction support)?
Thank you

Deepak, I don't think you know what you're writing about.
No, we do not support java.util.Set in <af:table>. For that matter, neither does <h:dataTable>.
The "why" of it is that we require indexed access into the table for operations like "Display rows 526-550". java.util.Set does not offer indexed access.
By the way, one corollary - do not use java.util.LinkedList with tables (ADF Faces or the JSF data table). If the list is small, then it won't be a problem, but with a large list, you'll get brutal performance.

OracleLog.properties for java.util.logging

In the Oracle JDBC FAQ the answer to the question "How do I configure java.util.logging to get useful trace output from Oracle JDBC?" <http://otn.oracle.com/tech/java/sqlj_jdbc/htdocs/jdbc_faq.htm#36_03> mentions the file "OracleLog.properties" provided in the "demo.zip" file.
I cannot find the file "OracleLog.properties" anywhere?
Any suggestions?
Kindest Regards,
Gerhard Hofmann

It seems a logger instance HAS been created for my Test class, I've added the lines below. Though it didn't appear in the logger names enumeration.
java.util.logging.Logger logger = java.util.logging.Logger.getLogger(name);
System.out.println(logger.getName()+"="+logger.getLevel().getName());
logger.severe("severe");
logger.warning("warning");
logger.info("info");
logger.config("config");
logger.fine("fine");
logger.finer("finer");
logger.finest("finest");Output:Test=FINEST
6/10/2003 16:00:01 Test <init>
SEVERE: severe
6/10/2003 16:00:01 Test <init>
WARNING: warning
6/10/2003 16:00:01 Test <init>
INFO: infoObservations:
1) Despite my Test class having the FINEST log level, the default ConsoleHandler had log level of INFO, and hence only up to INFO logged.

How can I define "java.util.ResourceBundle" in my Code ?

Dear Mr. MLRon,
Thanks to you for your replying to me.
How can I define "java.util.ResourceBundle" in my Code ? To more understanding about my problem I can say that the Persian Font is Like as Arabic, but the Java can not Recognize it. please tell me how can I add "java.util.ResourceBundle" to my code and what should I do then?
Thank you in advance,
Tantan.

Please stop starting new threads for this. Please reply in the original thread!
http://forum.java.sun.com/thread.jspa?threadID=627917

Using ExecutorService class from java.util.concurrent package

Dear java programmers,
I have a question regarding the ExecutorService class from java.util.concurrent package.
I want to parse hundreds of files and for this purpose I'm implementing a thread pool. The way I use the ExecutorService class is summarized below:
ExecutorService executor = Executors.newFixedThreadPool(10);
        for (int i = 0; i < 1000; i++){
            System.out.println("Parsing file No "+i);
            executor.submit(new Dock(i));
        executor.shutdown();
        try {
            executor.awaitTermination(30, TimeUnit.SECONDS);
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        executor.shutdownNow();However, the code snippet above creates all the 1000 threads (Dock objects) at once and loads them to the executor, and thus I'm worrying about memory leak. I haven't tested it on 1000 files yet but just on 50 small ones, and even if the program prints out "Parsing file No "+i 50 times at once, it executes normally the threads in the background.
I guess the write way would be to keep the number of active/idle threads in the executor constant (lets say 20 if the thread pool's size is 10) and submit a new one whenever a thread has been finished or terminated. But for this to happen the program should be notified someway whenever a thread is done. Can anybody help me do that?
thanks in advance,
Tom

Ok I found a feasible solution myself although I'm not sure if this is the optimum.
Here's what I did:
        ExecutorService executor = Executors.newFixedThreadPool(10);
        Future<String> future0, future1, future2, future3, future4, future5, future6, future7, future8, future9;
        Future[] futureArray = {future0 = null, future1 = null, future2 = null, future3 = null, future4 = null, future5 = null,
        future6 = null, future7 = null, future8 = null, future9 = null};
        for (int i = 0; i < 10; i++){
            futureArray[i] = executor.submit(new Dock(i));
        }I created the ExecutorService object which encapsulates the thread pool and then created 10 Future objects (java.util.concurrent.Future) and added them into an Array.
For java.util.concurrent.Future and Callable Interface usage refer to:
[http://www.swingwiki.org/best:use_worker_thread_for_long_operations]
[http://www.particle.kth.se/~lindsey/JavaCourse/Book/Part1/Java/Chapter10/concurrencyTools.html]
I used a Future[] Array to make the code neater. So after that I submitted -and in this way filled up- the first 10 threads to the thread pool.
        int i = 9;
        while (i < 1000){
            for (int j = 0; j < 10; j++){
                if (futureArray[j].isDone() && i < 999){
                    try{
                        i++;
                        futureArray[j] = executor.submit(new Dock(i));
                    } catch (ExecutionException ex) {
                        ex.printStackTrace();
                    } catch (InterruptedException ex) {
                        ex.printStackTrace();
            try {
                Thread.sleep(100); // wait a while
            } catch(InterruptedException iex) { /* ignore */ }
        executor.shutdown();
        try {
            executor.awaitTermination(60, TimeUnit.SECONDS);
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        executor.shutdownNow();
    }Each of the future[0-9] objects represents a thread in the thread pool. So essentially I'm check which of these 10 threads has been finished (using the java.util.concurrent.Future.isDone() method) and if yes I replenish that empty future[0-9] object with a new one.

Failed to unmarshal interface java.util.Set

I am trying to get all mbeans using getAllMBeans() method after
getting MBeanHome successfully. The method fails with the following
error.
Any clues ?
Thanks
karthik
>>>>
weblogic.rmi.extensions.RemoteRuntimeException: Unexpected Exception -
with nested exception:
[java.rmi.UnmarshalException: failed to unmarshal interface
java.util.Set; nested exception is:
     java.io.InvalidClassException: javax.management.MBeanAttributeInfo;
local class incompatible: stream classdesc serialVersionUID =
7043855487133450673, local class serialVersionUID =
8644704819898565848]
     at weblogic.management.internal.AdminMBeanHomeImpl_WLStub.getAllMBeans(Unknown
Source)

I am trying to get all mbeans using getAllMBeans() method after
getting MBeanHome successfully. The method fails with the following
error.
Any clues ?
Thanks
karthik
>>>>
weblogic.rmi.extensions.RemoteRuntimeException: Unexpected Exception -
with nested exception:
[java.rmi.UnmarshalException: failed to unmarshal interface
java.util.Set; nested exception is:
     java.io.InvalidClassException: javax.management.MBeanAttributeInfo;
local class incompatible: stream classdesc serialVersionUID =
7043855487133450673, local class serialVersionUID =
8644704819898565848]
     at weblogic.management.internal.AdminMBeanHomeImpl_WLStub.getAllMBeans(Unknown
Source)

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.

TestNG with java.util.Set

hi, i want to test simple method:
@Parameters({"lista"})
@Test
public GroupedFiles groupFiles(Set<File> p_files){
}and i have definition of my xml:
<suite name="My suite">
<parameter name="first-name" value="Cedric"/>
<test name="Simple example">
<-- ... -->and my testNG throws me uknown for me exception:
java.lang.AssertionError: Unsupported type parameter : interface java.util.Set
could anyone help me with this case, thanks for any knowledge

'little code modification'
hi, i want to test simple method:
@Parameters({"lista"})
@Test
public GroupedFiles groupFiles(Set<File> p_files){
}and i have definition of my xml:
<suite name="My suite">
<parameter name="lista" value="java.util.Set"/>
<test name="Simple example">
<-- ... -->and my testNG throws me uknown for me exception:
java.lang.AssertionError: Unsupported type parameter : interface java.util.Set
could anyone help me with this case, thanks for any knowledge

Getting compilation error: java.util.Set is an interface. This interface is not supported.

Hi Folks,
Is there a limitation in BEA's web services implementation? I have a simple web
service that returns an array of java objects. However I am calling another middle
tier API that returns a Set. I convert this Set into array of object and return
it via the web service.
However the .jws file that implements the webservice does not compile. I get the
following error message:
java.util.Set is an interface. This interface is not supported.
Is there a limitation on using Collections within the .jws file? If that is the
case it is a severe limitation.
Note my Web Service API returns an array of java objects with no collections in
them.
Sanjay

Hello,
Generic java collections can only be handled in a very generic, weakly
typed manner.
Take a look at the
http://workshop.bea.com/xmlbeans/guide/conXMLBeansSupportBuiltInSchemaTypes.html
and also
http://workshop.bea.com/xmlbeans/guide/conJavaTypesGeneratedFromUserDerived.html
You might also ask your question to the XMLBeans newsgroup:
http://newsgroups.bea.com/cgi-bin/dnewsweb?cmd=xover&group=weblogic.developer.interest.xmlbeans
Regards,
Bruce
Sanjay wrote:
>
Hi Folks,
Is there a limitation in BEA's web services implementation? I have a simple web
service that returns an array of java objects. However I am calling another middle
tier API that returns a Set. I convert this Set into array of object and return
it via the web service.
However the .jws file that implements the webservice does not compile. I get the
following error message:
java.util.Set is an interface. This interface is not supported.
Is there a limitation on using Collections within the .jws file? If that is the
case it is a severe limitation.
Note my Web Service API returns an array of java objects with no collections in
them.
Sanjay

RFC used for java.util.regex

Hi,
Does anyone know the RFC used for java.util.regex ??
Thanks & Regards,
Gurushant Hanchinal

Can you please give me the link to view to specifications for java.util.regex.. I have tried the link which is available in :
http://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.html page with name " Java Language Specification"
on click of this link, i am getting page not found error..
Please give me any other alternate links to view the regular expression specifications..
Thanks,
Gurushant Hanchinal

Most commenly used abstract class in java.

hi all,
can anyone please tell me, what is most commonly used abstract class in java. this question was asked in interview.

I hate interviewers when they ask about specifics of some classes.The fact that you hate it doesn't automatically follow that it's a bad question from the perspective of the person conducting the interviewer. You don't know what the real question is.
Bad "real" question: Do you know the statistics of Java usage off the top of your head?
Good "real" question: Do you know that Object isn't Abstract and can you name a few Abstract classes off the cuff?
Even then Programmers are so literal minded - the real question may be "Talk about what you know a bit."

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();
}

How can i compare: java.util.Date oracle.jbo.domain.Date?

I have made a ViewObject wich contains a date column.
I want to check if this date is smaller/greater than sysdate:
i get following error:
Error(45,24): method <(java.util.Date, oracle.jbo.domain.Date) not found in class Class4
code:
SimpleTimeZone pdt = new SimpleTimeZone(-8 * 60 * 60 * 1000, ids[0]);
// set up rules for daylight savings time
pdt.setStartRule(Calendar.APRIL, 1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);
pdt.setEndRule(Calendar.OCTOBER, -1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);
// create a GregorianCalendar with the Pacific Daylight time zone
// and the current date and time
Calendar calendar = new GregorianCalendar(pdt);
Date trialTime = new Date();
calendar.setTime(trialTime);
(VO_ULNRow)singleRow = null;
while(vo.hasNext()){ // ViewObject vo;
singleRow = (VO_ULNRow)vo.next();
if(calendar.getTime() < singleRow.getEO_ULN_BORROWFROM()); //singleRow returns oracle.jbo.domain.Date
etcetera
how can i compare those 2?

Hi,
oracle.jbo.domain.Date has two methods which suit your needs
longValue() which returns a long (though I'm not sure if returns a long comparable to the long returned by java.util.Date)
and dateValue() which returns a java.util.Date
I hope it helps,
Giovanni

Why how Abstract class for java.util.set

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