Why is sizeof operator not in java ?

Hello friends..
I am having one doubt.
Why is sizeof operator not in java ?
Can anybody please help ?
Thanks and Regards
Rohit.

An object often refers to other objects. These object may or may not have multiple references (so counting them more than once is not accurate) The actual amount of memory used is often greater than you might expect if you are used to C/C++. The system also uses memory in sometime unpredicable ways. Many methods create transient objects adding to your memory requirement. Shared libraries, the stack, the JVM itself do not appear in the heap size but use memory. Files accessed by the application can be significantly effect the desirable file cache size.
The only real way to determine your application's memory requirement is to actively test the application, anything else is just guess work.

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{color}
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Edited by: Jethro-Soft on Jun 30, 2008 8:49 PM
Edited by: Jethro-Soft on Jun 30, 2008 8:52 PM

Please check:
http://joust.kano.net/weblog/archive/2006/04/06/why-i-will-never-deploy-with-java-web-start-again/
http://kylecordes.com/2006/04/08/auto-update-no-web-start/

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I am using winXP.I have installed J2SE 5.0 by
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JWSDP 1.6. install script, there is always a message
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c:\Sun\AppServer
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c:\Sun\AppServer\jdk
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Java is considered to be a much better programming
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2) Statement 2 is for a quick lookup I perform (on a different table) for each item in the iteration.
3) Statement 3 is for the Insert statement which I perform for each item in the iteration. Again, I insert into a different table and I use "executeUpdate"
Given the I have three different statements and I am working with three different tables, why does my main result set that I am iterating through keep closing on me?
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java.sql.SQLException: Operation not allowed after ResultSet closed
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at com.mysql.jdbc.ResultSet.next(ResultSet.java:2468)
at com.mysql.jdbc.UpdatableResultSet.next(UpdatableResultSet.java:565)
Thanks for your help.

I have a very short piece of code. I use one
connection to the database. I execute a query, get
back a lot of rows, then iterate through the result
set and for each row I get some information and then
perform an insert into a different table.Sounds like a classic case of making Java do what the database was made to do.
I'd bet you can do this in a single INSERT with a SELECT in the database in one network roundtrip. The "quick lookup" might be a JOIN or a sub-SELECT. When you do a query, bring N rows back to the middle tier, then do an INSERT for each row that you retrieve it means (N+1) network roundtrips if you don't batch your INSERTs. I'd have a SQL expert give your code a look.
The problem is that the big result set I am iterating
through keeps closing sometime during the first
iteration. Why? I am using three different
statements:
1) Statement 1 is for the main query I want to
iterate through
2) Statement 2 is for a quick lookup I perform (on a
different table) for each item in the iteration.
3) Statement 3 is for the Insert statement which I
perform for each item in the iteration. Again, I
insert into a different table and I use
"executeUpdate"
Given the I have three different statements and I am
working with three different tables, why does my main
result set that I am iterating through keep closing
on me?Maybe your ResultSet or Statement goes out of scope. Do the Statements share a Connection?
%

CVI2010 sizeof-operator returns a wrong size of a struct

Hi,
in CVI2010 the sizeof-operator returns a wrong size of a struct, if it contains 4 bytes and other spaces. I suppose the adresses in the struct are also not like a c-programmer thinks. First a minimalistic code-example:
typedef struct
char oneByte;
long fourByte;
} TestStruct;
void main( )
   int size;
   TestStruct tmpVar;
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Since the last years and the last cvi-versions i had ever compiled
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project can't work with.
Because i'm reading the struct direct out of binary files i'm searching for a, not code based, solution.
Is it possible to deactivate the relevant optimization?
Thanks for your help and answer.
Markus
Solved!
Go to Solution.

The compiler can have different alignments for struct fields: a usual behaviour is to have them aligned on a 4-byte boundary, that is every field starts on a multiple of 4 bytes from the beginning of the struct in memory. This appears to be the behaviour of the compiler you are using at the moment, which returns 8 as the size of the struct having aligned the fields.
Struct alignment can be modified with an appropriate #pragma preprocessor instruction: adding #pragma pack (1); in your code instructs the compiler to pack structure fields without padding; after this instruction sizeof will return the 5-bytes dimension you are expecting.
Proud to use LW/CVI from 3.1 on.
My contributions to the Developer Zone Community
If I have helped you, why not giving me a kudos?

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Hello,
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(Error code - 36)"
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Most of the files work fine. However some of the files cause disc burner to not be able to use them in the disc image before I burn. Why would this be?
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Am I doing this the right way?
Why are some files not "readable or writeable" as it indicates in the error message?
Is my 4 GIG startup disk too small for this? or are the music files possibly corrupt? or could there be some other possible problem?
Thanks

To follow up, I have some good news. After following your advice Kappy, it now works very well Thanks! Instead of using the 4 GIG volume for the OS, I am now using an 8 GIG partition on an 80 GIG drive. So now the OS has some room to operate. No disk errors occured on my first DVD
Now there was one problem. The second DVD burned gave me an error. I am not sure why but I am going to guess that because I had to installed the OS onto an 8 GIG partition maybe the OS needs to be rebooted in between disk burns because although 8 GIGs is certainly greater than the 4 GIGs I gave it last time, it still isn't a lot of space - maybe just enough to do one DVD at a time. Thats only a guess. So I rebooted to see if that clears the system out ready for the next DVD and I am trying to burn the second DVD again. If I remember I will report back. In any case, yes, this seems to be working. I hope this second DVD burns well too.
Thanks Kappy

Why Oracle 8i is not Working with JDK 1.3

Why Oracle 8i is not Working with JDK 1.3 by using JDBC.

try this
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Why does for-each not work with Enumeration?

I'm sure there's some reason for this but I don't know what it would be.
I am calling an existing method [http://java.sun.com/javase/6/docs/api/java/util/zip/ZipFile.html#entries()] And it returns Enumeration<? extends ZipEntry>
What I would like to do is
Enumeration<? extends ZipEntry> entries = myzipfile.entries();
for(ZipEntry ze : entries)but this won't compile because Enumeration is not an Iterator. Which kinda sucks.
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Still it does'nt fully answer the why question. Why does the Collections class not implement a static iterable(Enumeration) method that does not impose the overhead of an addiditional ArrayList, as in the following class:
import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
public class EnumerationToIterable {
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          return new Iterator<T>() {
              @Override
              public boolean hasNext() {
               return enumeration.hasMoreElements();
              @Override
              public T next() {
               return enumeration.nextElement();
              @Override
              public void remove() {
               throw new UnsupportedOperationException();
    public void iterateOne(ZipFile myzipfile) {
     Enumeration<? extends ZipEntry> entries = myzipfile.entries();
     for (ZipEntry ze : Collections.list(entries)) {
         // process ze
    public void iterateTwo(ZipFile myzipfile) {
     Enumeration<? extends ZipEntry> entries = myzipfile.entries();
     for (ZipEntry ze : iterable(entries)) {
         // process ze
}Could it be more simple?
(Thanks for the Dukes)
Piet

Why is sizeof operator not in java ?

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