Re: [OT] how to calculate the size of an object
I wrote a simple test.
VO.java is a simple value object class with a couple of Strings and an
int as instance fields.
SerTest.java creates a number of instances of VO, inserts them into a
HashMap, and then serializes the entire map to a ByteArrayOutputStream.
Finally it prints the length of the resulting byte array in KB to
standard out.
You specify how many VO instances to put in the HashMap with args[0].
Notice that each VO's name field gets a new String object -- not a
shared one.
Here are some results. I notice a pattern:
java SerTest 1
size of map = 0.2373046875 kb
java SerTest 10
size of map = 0.5625 kb
java SerTest 100
size of map = 3.990234375 kb
java SerTest 1000
size of map = 40.025390625 kb
java SerTest 1
size of map = 417.955078125 kb
java SerTest 10
size of map = 4373.033203125 kb
simarjit singh wrote:
With ByteArrayOutputStream approach, writeObject Method is also serializing
the object. Ofcourse serialization doesn't give size as it is more of a meta
data for the entire web of objects associated with the serialized object.
Rather than writing serialized object on file we are putting it in a byte
array stream.
What u are getting is NOT bytes for object but bytes for serliazed data
Correct me if i am wrong...
-Simar
You are right, serialization includes meta data, but, the bytes for
serialized data certainly *contains* the bytes for object! So, while
the *absolute* accuracy of this data may be somewhat suspect
(serialization overhead needs to be subtracted, for one), the point is
that it is more than likely useful and probably gives a good ballpark
idea of how big an object is. As I understand it, serialization overhead
represents only a fraction of those bytes.
It would be interesting to see a comparison using the other method of
determining memory use and see how it comes out!
I'll tell you who would be a good authority on this subject, is Bill
Venners over at Artima.com.
Good luck!
Erik
import java.util.HashMap;
import java.io.ObjectOutputStream;
import java.io.ByteArrayOutputStream;
public class SerTest {
public static void main(String[] args) throws Exception {
int count = Integer.parseInt(args[0]);
HashMap map = new HashMap();
for (int x = 0; x count; x++) {
map.put(new Integer(x), new VO(new String(John Doe + x),
String.valueOf(x), (int) (Math.random() * 100)));
}
printSize(map);
}
public static void printSize(Object o) throws Exception {
ByteArrayOutputStream bs = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(bs);
out.writeObject(o);
out.close();
double size = bs.toByteArray().length;
System.out.println(size of map = + ((double) (size / 1024D)) + kb);
}
}
import java.io.Serializable;
public class VO implements Serializable {
protected String name;
protected String ID;
protected int age;
public VO(String name, String ID, int age) {
this.name = name;
this.ID = ID;
this.age = age;
}
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setID(String ID) {
this.ID = ID;
}
public String getID() {
return ID;
}
public void setAge(int age) {
this.age = age;
}
public int getAge() {
return age;
}
}
-Original Message-
From: Erik Weber [mailto:[EMAIL PROTECTED]
Sent: Thursday, July 08, 2004 10:57 PM
To: Struts Users Mailing List
Subject: Re: [OT] how to calculate the size of an object
Also remember that when you serialize an Object (if I am not mistaken),
all the Objects referred to by that Object get serialized too (unless
the references are transient). In addition, there is serialization
overhead (protocol info that is not actually part of your Object but
that is required to deserialize). Your returned size could be misleading
if you have references to, say, some parent Object(s) in LDIFData, or
a ton of serialization overhead (unlikely).
Erik
Erik Weber wrote:
public static long getSize(LDIFData data) {
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(baos);
out.writeObject(data);
out.close();
return baos.toByteArray().length;
}
catch (Exception e) {
e.printStackTrace();
return -1;
}
}
John Moore wrote:
Navjot Singh wrote:
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How to do
that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
Off the top of my head...
Serialize it to a byte array output stream, see how many bytes you have
John
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Re: [OT] how to calculate the size of an object
Here's a concrete example. First, the Java class:
public class JvmtiSize {
public static native long getObjectSize(Object o);
public static void main(String[] args) {
String s = Hello, world!;
String[] sa = { s };
System.out.printf(s: %6d bytes\n, getObjectSize(s));
System.out.printf( sa: %6d bytes\n, getObjectSize(sa));
System.out.printf(class: %6d bytes\n,
getObjectSize(JvmtiSize.class));
}
}
Then, run javah to generate JvmtiSize.h (omitted). Next, the C code
(jvmti_size.c):
#include jvmti.h
#include JvmtiSize.h
JavaVM *global_jvm = NULL;
JNIEXPORT jint JNICALL
Agent_OnLoad(JavaVM *jvm, char *options, void *reserved) {
global_jvm = jvm;
return 0;
}
JNIEXPORT jlong JNICALL
Java_JvmtiSize_getObjectSize(JNIEnv *env, jclass class, jobject object) {
jint status;
jvmtiEnv *jvmti;
jvmtiError err;
jlong object_size;
status = (*global_jvm)-GetEnv(global_jvm, (void **)jvmti, JVMTI_VERSION);
if (status != JNI_OK) {
fprintf(stderr,
ERROR: Unable to create jvmtiEnv (GetEnv failed), error=%d\n,
status);
exit(1);
}
err = (*jvmti)-GetObjectSize(jvmti, object, object_size);
if (err != JVMTI_ERROR_NONE) {
fprintf(stderr,
ERROR: GetObjectSize failed, error=%d\n,
err);
exit(1);
}
return object_size;
}
Then, generate the shared lib (Solaris SPARC):
cc -G -I${JAVA_HOME}/include -Isrc -I${JAVA_HOME}/include/solaris
src/jvmti_size.c -o libjvmti_size.so
Finally, give it a run:
java -agentlib:jvmti_size -cp classes JvmtiSize
s: 24 bytes
sa: 16 bytes
class:288 bytes
Quoting Kris Schneider [EMAIL PROTECTED]:
Not too surprising that it's available through a native programming
interface
(JVMTI) since it's really an implementation-dependent metric:
http://java.sun.com/j2se/1.5.0/docs/guide/jvmti/jvmti.html#GetObjectSize
Quoting Brian Lee [EMAIL PROTECTED]:
If you run this from a simple console test app, the JVM won't allocate any
extra objects between 2 and 4.
Unfortunatly, this is the most exact way to find out memory usage
(serialization size doesn't necessarily mean in memory size).
Just wait til those slackers at Sun at a Object.sizeof() method in jdk1.9
or
something lame.
BAL
From: Navjot Singh [EMAIL PROTECTED]
To: Struts Users Mailing List [EMAIL PROTECTED]
Subject: Re: [OT] how to calculate the size of an object
Date: Thu, 08 Jul 2004 22:16:12 +0530
hi,
Thanks for the link but this is very naive way of doing it. I am leaving
it
to the mercy of gc.
What this method is doing
1. run gc() manually (AND hope it wont run automatically again soon.)
2. free memory
3. create and object.
4. free memory
and now just wish that JVM wont allocate any memory in it's heap between
steps 2 4. so that one can assume that whatsoever output comes belongs
to
my object. I am at something better.
Jim you are absolutely right, this technique may return a negative
number.
navjot singh
[EMAIL PROTECTED] wrote:
http://www.google.com/search?hl=enlr=ie=UTF-8q=size+java+object
The first one looks promising.
Dennis
*Navjot Singh [EMAIL PROTECTED]*
07/08/2004 11:57 AM
Please respond to
Struts Users Mailing List [EMAIL PROTECTED]
To
Struts Users Mailing List [EMAIL PROTECTED]
cc
Subject
[OT] how to calculate the size of an object
hi,
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How to do that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
--
regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
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regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
--
Kris Schneider mailto:[EMAIL PROTECTED]
D.O.Tech http://www.dotech.com/
--
Kris Schneider mailto:[EMAIL PROTECTED]
D.O.Tech http://www.dotech.com/
[OT] how to calculate the size of an object
hi,
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How to do that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
--
regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
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To unsubscribe, e-mail: [EMAIL PROTECTED]
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Re: [OT] how to calculate the size of an object
Navjot Singh wrote:
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How to do that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
Off the top of my head...
Serialize it to a byte array output stream, see how many bytes you have
John
--
==
John Moore - Norwich, UK - [EMAIL PROTECTED]
==
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RE: [OT] how to calculate the size of an object
java.io.File has the length() method to return the length of the file.
-Original Message-
From: Navjot Singh [mailto:[EMAIL PROTECTED]
Sent: Thursday, July 08, 2004 8:58 AM
To: Struts Users Mailing List
Subject: [OT] how to calculate the size of an object
hi,
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How
to do that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
--
regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground
from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
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Re: [OT] how to calculate the size of an object
http://www.google.com/search?hl=enlr=ie=UTF-8q=size+java+object
The first one looks promising.
Dennis
Navjot Singh [EMAIL PROTECTED]
07/08/2004 11:57 AM
Please respond to
Struts Users Mailing List [EMAIL PROTECTED]
To
Struts Users Mailing List
[EMAIL PROTECTED]
cc
Subject
[OT] how to calculate the
size of an object
hi,
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How to do that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
--
regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
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RE: [OT] how to calculate the size of an object
Only problem is, that this is the size of the object with a new object, rather then
being something that could be done dynamically. Not to mention
that if this is done at run time ( which is what the original poster wants I believe)
then you can be completely screwed by a GC run, and end up
with a negative number.
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Thursday, July 08, 2004 9:10 AM
To: Struts Users Mailing List
Subject: Re: [OT] how to calculate the size of an object
http://www.google.com/search?hl=enlr=ie=UTF-8q=size+java+object
The first one looks promising.
Dennis
Navjot Singh [EMAIL PROTECTED]
07/08/2004 11:57 AM
Please respond to
Struts Users Mailing List [EMAIL PROTECTED]
To
Struts Users Mailing List [EMAIL PROTECTED]
cc
Subject
[OT] how to calculate the size of an object
hi,
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How to do that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
--
regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
RE: [OT] how to calculate the size of an object
Whoops.. that should the problem with the first one on the list.. :)
I know Bad code monkey no caffeine.
-Original Message-
From: Jim Barrows
Sent: Thursday, July 08, 2004 9:24 AM
To: Struts Users Mailing List
Subject: RE: [OT] how to calculate the size of an object
Only problem is, that this is the size of the object with a
new object, rather then being something that could be done
dynamically. Not to mention
that if this is done at run time ( which is what the original
poster wants I believe) then you can be completely screwed by
a GC run, and end up
with a negative number.
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]
Sent: Thursday, July 08, 2004 9:10 AM
To: Struts Users Mailing List
Subject: Re: [OT] how to calculate the size of an object
http://www.google.com/search?hl=enlr=ie=UTF-8q=size+java+object
The first one looks promising.
Dennis
Navjot Singh [EMAIL PROTECTED]
07/08/2004 11:57 AM
Please respond to
Struts Users Mailing List [EMAIL PROTECTED]
To
Struts Users Mailing List [EMAIL PROTECTED]
cc
Subject
[OT] how to calculate the size of an object
hi,
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How
to do that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
--
regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground
from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
RE: [OT] how to calculate the size of an object
-Original Message-
From: Navjot Singh [mailto:[EMAIL PROTECTED]
Sent: Thursday, July 08, 2004 9:46 AM
To: Struts Users Mailing List
Subject: Re: [OT] how to calculate the size of an object
hi,
Thanks for the link but this is very naive way of doing it. I
am leaving
it to the mercy of gc.
Look at some of the other articles.. you'll find some better articles there on how to
do it.
What this method is doing
1. run gc() manually (AND hope it wont run automatically again soon.)
2. free memory
3. create and object.
4. free memory
and now just wish that JVM wont allocate any memory in it's
heap between
steps 2 4. so that one can assume that whatsoever output
comes belongs
to my object. I am at something better.
Jim you are absolutely right, this technique may return a
negative number.
navjot singh
[EMAIL PROTECTED] wrote:
http://www.google.com/search?hl=enlr=ie=UTF-8q=size+java+object
The first one looks promising.
Dennis
*Navjot Singh [EMAIL PROTECTED]*
07/08/2004 11:57 AM
Please respond to
Struts Users Mailing List [EMAIL PROTECTED]
To
Struts Users Mailing List [EMAIL PROTECTED]
cc
Subject
[OT] how to calculate the size of an object
hi,
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime.
How to do that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
--
regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground
from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
--
--
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--
regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground
from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
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Re: [OT] how to calculate the size of an object
public static long getSize(LDIFData data) {
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(baos);
out.writeObject(data);
out.close();
return baos.toByteArray().length;
}
catch (Exception e) {
e.printStackTrace();
return -1;
}
}
John Moore wrote:
Navjot Singh wrote:
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How to do that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
Off the top of my head...
Serialize it to a byte array output stream, see how many bytes you have
John
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To unsubscribe, e-mail: [EMAIL PROTECTED]
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Re: [OT] how to calculate the size of an object
Also remember that when you serialize an Object (if I am not mistaken),
all the Objects referred to by that Object get serialized too (unless
the references are transient). In addition, there is serialization
overhead (protocol info that is not actually part of your Object but
that is required to deserialize). Your returned size could be misleading
if you have references to, say, some parent Object(s) in LDIFData, or
a ton of serialization overhead (unlikely).
Erik
Erik Weber wrote:
public static long getSize(LDIFData data) {
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(baos);
out.writeObject(data);
out.close();
return baos.toByteArray().length;
}
catch (Exception e) {
e.printStackTrace();
return -1;
}
}
John Moore wrote:
Navjot Singh wrote:
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How to do
that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
Off the top of my head...
Serialize it to a byte array output stream, see how many bytes you have
John
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
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To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
Re: [OT] how to calculate the size of an object
If you run this from a simple console test app, the JVM won't allocate any
extra objects between 2 and 4.
Unfortunatly, this is the most exact way to find out memory usage
(serialization size doesn't necessarily mean in memory size).
Just wait til those slackers at Sun at a Object.sizeof() method in jdk1.9 or
something lame.
BAL
From: Navjot Singh [EMAIL PROTECTED]
To: Struts Users Mailing List [EMAIL PROTECTED]
Subject: Re: [OT] how to calculate the size of an object
Date: Thu, 08 Jul 2004 22:16:12 +0530
hi,
Thanks for the link but this is very naive way of doing it. I am leaving it
to the mercy of gc.
What this method is doing
1. run gc() manually (AND hope it wont run automatically again soon.)
2. free memory
3. create and object.
4. free memory
and now just wish that JVM wont allocate any memory in it's heap between
steps 2 4. so that one can assume that whatsoever output comes belongs to
my object. I am at something better.
Jim you are absolutely right, this technique may return a negative number.
navjot singh
[EMAIL PROTECTED] wrote:
http://www.google.com/search?hl=enlr=ie=UTF-8q=size+java+object
The first one looks promising.
Dennis
*Navjot Singh [EMAIL PROTECTED]*
07/08/2004 11:57 AM
Please respond to
Struts Users Mailing List [EMAIL PROTECTED]
To
Struts Users Mailing List [EMAIL PROTECTED]
cc
Subject
[OT] how to calculate the size of an object
hi,
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How to do that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
--
regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
--
regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
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Re: [OT] how to calculate the size of an object
Not too surprising that it's available through a native programming interface
(JVMTI) since it's really an implementation-dependent metric:
http://java.sun.com/j2se/1.5.0/docs/guide/jvmti/jvmti.html#GetObjectSize
Quoting Brian Lee [EMAIL PROTECTED]:
If you run this from a simple console test app, the JVM won't allocate any
extra objects between 2 and 4.
Unfortunatly, this is the most exact way to find out memory usage
(serialization size doesn't necessarily mean in memory size).
Just wait til those slackers at Sun at a Object.sizeof() method in jdk1.9 or
something lame.
BAL
From: Navjot Singh [EMAIL PROTECTED]
To: Struts Users Mailing List [EMAIL PROTECTED]
Subject: Re: [OT] how to calculate the size of an object
Date: Thu, 08 Jul 2004 22:16:12 +0530
hi,
Thanks for the link but this is very naive way of doing it. I am leaving it
to the mercy of gc.
What this method is doing
1. run gc() manually (AND hope it wont run automatically again soon.)
2. free memory
3. create and object.
4. free memory
and now just wish that JVM wont allocate any memory in it's heap between
steps 2 4. so that one can assume that whatsoever output comes belongs to
my object. I am at something better.
Jim you are absolutely right, this technique may return a negative number.
navjot singh
[EMAIL PROTECTED] wrote:
http://www.google.com/search?hl=enlr=ie=UTF-8q=size+java+object
The first one looks promising.
Dennis
*Navjot Singh [EMAIL PROTECTED]*
07/08/2004 11:57 AM
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[OT] how to calculate the size of an object
hi,
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How to do that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
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regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
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regards
Navjot Singh
When you jump for joy, beware that no-one moves the ground from beneath
your feet. -- Stanislaw Lem, Unkempt Thoughts
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Kris Schneider mailto:[EMAIL PROTECTED]
D.O.Tech http://www.dotech.com/
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RE: [OT] how to calculate the size of an object
With ByteArrayOutputStream approach, writeObject Method is also serializing
the object. Ofcourse serialization doesn't give size as it is more of a meta
data for the entire web of objects associated with the serialized object.
Rather than writing serialized object on file we are putting it in a byte
array stream.
What u are getting is NOT bytes for object but bytes for serliazed data
Correct me if i am wrong...
-Simar
-Original Message-
From: Erik Weber [mailto:[EMAIL PROTECTED]
Sent: Thursday, July 08, 2004 10:57 PM
To: Struts Users Mailing List
Subject: Re: [OT] how to calculate the size of an object
Also remember that when you serialize an Object (if I am not mistaken),
all the Objects referred to by that Object get serialized too (unless
the references are transient). In addition, there is serialization
overhead (protocol info that is not actually part of your Object but
that is required to deserialize). Your returned size could be misleading
if you have references to, say, some parent Object(s) in LDIFData, or
a ton of serialization overhead (unlikely).
Erik
Erik Weber wrote:
public static long getSize(LDIFData data) {
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(baos);
out.writeObject(data);
out.close();
return baos.toByteArray().length;
}
catch (Exception e) {
e.printStackTrace();
return -1;
}
}
John Moore wrote:
Navjot Singh wrote:
I use SAX parser to load an LDIF file into memory. Whatsoever data i
read, i fill into an object.
I need to know *the size of LDIFData object* at runtime. How to do
that?
Well the class structure is something like this
public class LDIFData{
ArrayList cards; // collection of Card
String filename;
long lastLoadedTime;
}
public class Card{
String name;
String email
String mobile;
}
Off the top of my head...
Serialize it to a byte array output stream, see how many bytes you have
John
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