Difference between JVM and JRE

Hi,
can anyone tell me if there is a difference between a JVM and a JRE?
I'm trying to use Excelsior JET to make windows executables from java classes. The documentation says that with JET you dont need the JVM but reading between the lines I think you do still need the Java JRE.
Are these different or the same thing?
Cheers,
Jim

JRE = JVM + classes and libs.

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What is the difference between JVM and JRE and JDK?

Hi , I want to know what actually is JVM,JRE and JDK ? and the difference between them?

They should at least try. When it comes to
terminology, if they can find this site, they should
be able to find google, wikipedia, etc. It's
reasonable to expect them to try there first, and
then, if they still have questions, post here,
indicating what they looked at and how it fell short,
what they're still confused about, etc.Perhaps this is a valid point.
I believe physical JVM hardware has also been
manufactured. I wonder what we'd call that? A JPM
(Java Pysical Machine)?No. It is simply a hardware implementation of the abstract Java Virtual Machine.
.class files are executed by software (in fact,the
software that executes the .class files is calledthe
JRE and is short for the Java
Runtime Environment). The JavaRuntime
Environment is a native program (i.e. it is run by
hardware) which provides the ability to executejava
bytecodes (.class files)That's the JVM.No it's not. The JVM is an abstract architecture.
The JRE is the JVM plus native libraries plus core
API Java classes.The JRE is an implementation of the JVM along with some additional facilities. The JVM may be used to describe concrete implementations in industry vernacular, but this is not a technically accurate usage of the term per the specification and is therefore incorrect.
From the preface to the Java Virtual Machine Specification, Second Edition, viewable at http://java.sun.com/docs/books/jvms/second_edition/html/Preface.doc.html:
"The Java virtual machine is an abstract machine."
From Wikipedia (http://en.wikipedia.org/wiki/JVM):
"A Java Virtual Machine (JVM) is a set of computer software programs and data structures which implements a specific virtual machine model."
Perhaps this misconception is the source of the confusion. This is one reason why I answered deepakorsun rather than refer him to somewhere else: anywhere that would be reliable and/or completely accurate would be too dense to readily understand, and anywhere understood easily enough might not be completely accurate.
>
The Java Development Kit (JDK) just provides the
facilities necessary to write programs that willrun
on the Java Virtual Machine. It contains acompiler
It also contains tools such as jar and javap, the API
docs for the core API classes, the source code for
the API classes, probably a few other things, and
generally the JRE (though I'm not sure if that's
officially a required part of the JDK).I never said it didn't contain jar, javap, javac, java, jdb, jconsole, or any of the other programs or resources shipped with jdk. I simply stated affirmatively something it did contain. As I implied before, technical comprehensiveness is exactly what makes resources such as the JVM specification almost unusable for answering questions like this. That is why I omitted such details in my description. And since we're being all technical here, the API documentation does not ship with the Java Development Kit (at least not as of JDK 5.0), it is a separate download. It is the core API source files that ship in a .zip file with the JDK.
Don't get me wrong, I do understand that you have probably seen a lot more people come and go from these forums than I may ever understand and that you have helped more people than you can remember, and I don't mean to disrespect that. I understand that dealing with so many people over such a long period of time and hearing the same questions over and over again can probably start to wear on your patience, but I don't think the right approach is to treat anyone that tries to help them with utter contempt and sarcasm. That's not constructive or useful to anyone. I understand why you would be upset if somebody was purposely trying to be lazy, I probably would be too, but you have no real way of determining whether or not they are being lazy or just don't know something and don't know how to figure it out for themselves so they are asking a question. And if they are honestly just asking a question in good faith and looking up the answer on Wikipedia just did not occur to them (or they couldn't understand what it said), yet they somehow ended up on this site, they have done nothing wrong and there is no reason to get angry at them.
Oh come on, that wasn't nice. Not everybody isable
to answer their own questions. WTF are you talking about?!? Why waste the time to
type something out when they can click on a link and
find 1000 times more information than you can fit
into one post? Either way - they're
STILL going to have to read the
information themselves...
Ridiculous.So I suppose you've either read the Java Virtual Machine Specification, the Java Language Specification, and the Java Native Interface Specification in their entireties, or absolutely nothing about programming in Java. This is because, by your reasoning, these three books contain 1000 times more than anyone can fit on a tutorial, Wikipedia entry, mailing list, forum, blog, or anything else.
Criticizing somebody who isn't doing something the exact way you think it should be done is often quite idiotic and non-constructive. I believe this is this case here. Please post something more useful, meaningful, and/or polite next time. And just for future reference, yelling at a beginner does not help them learn faster or better. It just makes them hate you.
Oh come on, that wasn't nice. Not everybody isable
to answer their own questions. Java terminologycan
be confusing and difficult to understand in part
because of all the acronyms used and all the name
changes undergone by the various development kitsand
platforms.Point taken. You have much more patience than
I, but with lots of intensive therapy and proper
adjustment of my medications, I may get better.Thank you for this post. A display of wisdom and patience. You single handedly caused me to reconsider participating in a flame war.

What is the difference between JVM and JRE

hello everyone,
a funny but really confusing question is that how a virtual machine is different from a runtime environment.
some may argue that RE contains the API classes and implementations etc. but i need some real picture of what is the actual difference and anything related to this topic.
thanks,
waiting for your responses :-)

The Java Virtual Machine forms part of a large system, the Java Runtime Environment. Each operating system and CPU architecture requires a different JRE.
The JRE comprises a set of base classes, which are an implementation of the base Java API, as well as a JVM.

Whatz the difference between jdk and jre

i would like to know the difference between jdk and jre.

Yes JRE is Java Run Time Environment. The java programming language adds the portability by converting the source code to byte code version which can be interpreted by the JRE and gets converted to the platform specific executable ones. Thus for different platforms one has corresponding implementation of JRE. But JRE has to meet the specification JVM (Java Virtual Machine) Concept that serves as a link between the Java libraries and the platform specific implementation of JRE. Thus JVM helps in the abstraction of inner implementation from the programmers who make use of libraries for their programmes.
The JDK(Java Developmental Tool kit) comes along with java libraries and JVM embedded in it. Apart from these it comes along with the utility tools for byte code compilation "javac", Executing the byte codes through java programmes through "java" and many more utilities found in the binary directory of java. Speaking practically JDK is essential for developers, which comes along with library packages to develop Software programmes. While JRE is minimal set of programmes which executes the java class files developed by the software developers.

What is the difference between jdk and jre

what is the difference between jdk and jre
plzz tell me in detail

It's an extremely important skill to learn how to search the web. Not only will it increase your research and development talents, it will also save you from asking questions that have already been answered numerous times before. By doing a little research before you ask a question, you'll show that you're willing to work and learn without needing to have your hand held the entire time; a quality that is seemingly rare but much appreciated by the volunteers who are willing to help you.
If you've done the research, found nothing useful, and decide to post your question, it's a great idea to tell us that you've already searched (and what methodologies you used to do your research). That way, we don't refer you back to something you've already seen.
To get you started, here is an excellent resource: The Java� Glossary

Major Difference between JDK and JRE

Hi Support,
Major Difference between JDK and JRE
can you please distinguish between these two ,
Thanks

860707 wrote:
Hi Support,This isn't 'support' it's a forum.
Major Difference between JDK and JREYes, there is.
can you please distinguish between these two ,
Here.
db

Differences between jdk and jre

can anybody explain the differences between jdk and jvm. and relation between jdk, jre and jvm.
thanks

Hi,
JDK- Java Development Kit contains compiler and other appliction development tools. with this tool you can compile as well as run your application
JRE-Java runtime Environment where Java applications are exceuted .You can only run your application here but you cant develop and compile.
JVM-Java Virtual Machine Its interpretor which interprets and then executes you coded after it is compile ( to byte code) by Java Compiler.

Difference between jdk and jre...

Hi, I installed java (jdk1.6.0_03) and i got 2 folders in my pc with names jre1.6.0_03 and jdk1.6.0_03.
I don't know what are those. And while installing Tomcat5.0 it take the default path for jre1.6.0_03 and worked properly.
pls help me .......

JRE = Java Runtime Environment.
It's basically the implementation for your PC of the Java Virtual Machine (JVM) which is the software emulated processor that Java code runs on.
JDK = Java Development Kit
It's the JRE plus the compiler tools to allow you to write code.
Old versions of Tomcat needed the JDK because JSPs get converted into Java Servlet source code which is compiled into class files and run on the JVM. Newer versions of Tomcat only need the JRE because Tomcat now has its own compiler (implemented in Java) built in.
So since Tomcat's working, I don't think you have much to worry about :-)
Edited by: dcminter on 03-Jun-2008 10:28

Difference betweeen JDBC and JRE

Hi,
What is basic difference between JDBC and JRE?
JDBC used to connect jdbc connections (Application users ) to Database .
We use JRE to access forms only... is that correct ?
Please clarify
-Thanks

HI Hussein,
Thanks for the reply.
Can you please provide more information or Docs , how Autoconfig uses JDBC ?
HusseinSawwan wrote:
Vijay.Cherukuri wrote:
Hi,
What is basic difference between JDBC and JRE?
JDBC used to connect jdbc connections (Application users ) to Database .
We use JRE to access forms only... is that correct ?
Please clarify
-Thanks
Correct. JDBC is used by AutoConfig as well.
Thanks,
Hussein

Difference between JVM of web browser and JVM of webcontainer?

hi friends , I am babu pursuing mca final year
i have one doubt that is ........
What is the difference between JVM of web browser and JVM of web container ?
plz clarify my doubt

Who said there's a difference?
(By "web container" I assume you're talking about a servlet container or JSP container like tomcat.)

Difference between void and null?

wht is da difference between void and null w.r.t java?

corlettk wrote:
Why do you care, unless you're implementing a java compiler or JVM?Wow, you sure do suck at helping out in a forum. Why even make this post? You're not helping the OP any, and you made yourself look like a tool.
To the op:
Null is java's version of a null value. Java's version is more strict then many other languages, and will not work in a boolean expression or anywhere code expects a real and not null value. It's simply null.
Void is java's way of declaring no return type on a method. Methods that are void take no 'return' statement and if one is provided will cause a fatal error. The exception to this is using 'return' without a value, which returns control to the caller of the method.
Observe:
//this method returns an int
public int return_int(){
    int value = 5;
    return value;
//this method does not return an int
public void return_nothing(){
    int another_value = 123;
    System.out.println("Here's the value: " + return_int());
//this method does not return anything
public void nothing_returned(){
    return_nothing();
    return;
    System.out.println("This line never gets printed; the method returned control already!");
}

What is the difference between ojvm and client versions?

Changing the java vm from client to ojvm result in the following error:
Errormessage:
java.lang.UnsatisfiedLinkError: no UniqueC in java.library.path
Project Settings -> Configurations -> Development -> Runner -> Virtual Machine -> ojvm FAILS
Project Settings -> Configurations -> Development -> Runner -> Virtual Machine -> ojvm      RUNS OK.
Project Settings -> Configurations -> Development ->Paths ->Additional Classpath:
C:\jars\xerces.jar;C:\jars\UniqueC.dll;C:\jars\log4j-1.2.8.jar
What is the difference between ojvm and client versions? How can I make ojvm to find UniqueC.dll?
Various version info:
Output from program:
java version:1.4.2_01
java home:C:\programfiler\JAVA\2sdk1.4.2_01\jre
java vm version:9.0.3.738 cdov
Taken from JDeveloper Help About:
Oracle IDE     9.0.3.10.35
UML Modelers Version     9.0.3.9.4
Business Components Version     9.0.3.10.7
java.version     1.3.1_02
java.vm.name     OJVM Client VM
java.vm.version     9.0.3.738 o

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Difference between logical and virtual terms

Hello,
This is not purely oracle question; but in documentation so many times we find 2 terms:
A. Logical
B.Virtual.
So what is the principle difference between logical and virtual? As I know physical is that which I can see and touch; while logical/virtual is that is imaginary. We say tablespace is logical not virtual; while Java Virtual Machine; not Java Logical Machine. So I want to know; what is the principle difference; why two words for an imaginary thing. Before posting question; I searched in google as “Difference between virtual and logical” but I couldn’t found the answer.
Please quote your comments.
Thanks & Kind Regards
Girish Sharma

Girish,
I wont say that I am correcting you as this is like that half glass full/empty thing.May be what I see is half empty , you would see the same as half full.
Well now coming to the explanation.I am saying honestly , I got more confused after reading your definitions.What do you mean by saing that tablespace is not virtual.I see it as purely virtual.We don't say it as virtual tablespace or logical tablespace but it is actualy logical/virtual, having no existance but just the definition right?
How can you say that the size of virtual is larger than logcial?The size of tablespace is actualy the sum total of size of datafiles.So it actualy becomes very larger right?Much larger than JVM which is of few megs only.
The point 3 totally knocked me out.I have no idea what you said.
Ok I tell you this.Just remember the definition that Hans gave already.If you ask me than its the best definition that we can have. Just remember this and if some one asks you more further than give them your point 3 definition and tell them understand this ;-).Please don'tmind I am just kidding. Its just semantics.Don't get lost into it.You will find many people using both the terms interchangibly. So its ok.I shall stick with Hans's defintion,simple and concise.There are lot more other topics to dig upon in oracle.I can mail you lots of them.Spend time on those.Don't think that I am demotivating you.I understand you asked only because you have a doubt.But we got a good resolution of it and beyond that, its not of much use to dig it atleast not in the technial terms.
Cheers
Aman....
PS:Are you on oraclecommunity.net?

Find the difference between loading and registering the drivers..

Dear Sir..
Could you please help me to find the difference between two activities..
1.Loading the drivers
2.Registering the drivers
What's the difference between loading and registeing the drivers and what activities take place by the JVM to do it all.

Dear Sir..
Could you please help me to find the difference
between two activities..
1.Loading the drivers
2.Registering the drivers
What's the difference between loading and registeing
the drivers and what activities take place by the JVM
to do it all.You load a class - it isn't specific to a driver.
That is part of java - not JDBC.
Normally JDBC drivers register themselves when the class is loaded. This is specific to the driver and has nothing to do with a user of the driver. It is only a concern to someone who must implement a driver.

Difference Between Errors and Exception?

I want to know what is the difference between Error and Exception?

Everything is sadly enough catchable as Throwable but
you should never catch Errors. They are an indication
that something has gone wrong in the JVM and they are
not recoverable.Although it is clear that Sun recommends against catching Errors (".. indicates
serious problems that a reasonable application should not try to catch.. etc.."), sometimes, it makes sense to catch some type of Errors.
There was that Java editor (I forgot the name) which would catch OutOfMemoryErrors when the user would try to open a file that was too large.
So instead of crashing, the application would recover from the Error, and I personnally thought that was an interesting feature. At least, a better alternative than the whole application failing.

Difference between JVM and JRE

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