Run two java apps in separate jvm's on the same machine?

At the command line, when you type:
java MyClass
and then type:
java MyClass
are the two programs (assuming neither terminated prior to the other's execution) is it running in a separate Java Virtual Machine or the same one?
And if they're running in the same JVM, is there a way to run the second program in a separate JVM for testing purposes even though they're on the same computer? (btw I'm running windows XP).

thanks all...just a quick follow up question. Are two
separate jvm's on the same computer a good
representation of two jvms running on separate
computers?Don't know what you mean by "a good representation."
They're two separate processes. For basic testing, not worrying about performance, etc., and if your code doesn't do anything special to treat two VMs on the same box differently than two VMs on separate boxes, it's probably a reasonable approximation.

Similar Messages

How do I run multiple java apps in one JVM to reduce memory use?

Hi all,
I saw an article either on the web or in a magazine not too long ago about how to "detect" if the app is already running, and if so, it hands off the new instance to the already running JVM, which then creates a thread to run the Java app in. As it turns out, my app will be used in an ASP environment, through Citrix. We may have as many as 50 to 100 users running the same app, each with their own unique user ID, but all using the same one server to run it on. Each instance eats up 25MB of memory right now. So the question is if anybody knows of a URL or an app like this that can handle the process of running the same (or even different Java) apps in one JVM as separate threads, instead of requring several instances of the JVM to run? I know this article presented a fully working example, and I believe I know enough to do it but I wanted ot use the article as a reference to make sure it is done right. I know that each app basically would use the same one "launcher" program that would on first launch "listen" to a port, as well as send a message through the port to see if an existing launcher was running. If it does, it hands off the Java app to be run to the existing luancher application and shuts down the 2nd launching app. By using this method, the JVM eats up its normal memory, but each Java app only consumes its necessary memory as well and doesn't use up more JVM instance memory.
Thanks.

<pre>
import java.util.Properties;
import java.io.FileInputStream;
import java.io.IOException;
import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;
import java.util.Enumeration;
import java.util.NoSuchElementException;
public class RunProg implements Runnable, Cloneable
private String iProg;
private String iArgs[];
public static void main(String args[])
new RunProg().main();
// first step is to start main program itself
private void main()
Properties properties = System.getProperties();
try
properties.load(new FileInputStream("RunProg.properties"));
catch(IOException e)
System.setProperties(properties);
int i = 0;
System.out.println("enter main, activeCount=" + Thread.activeCount());
while(true)
String program = properties.getProperty("Prog" + i);
if(program == null)
break;
StringTokenizer st = new StringTokenizer(program);
String[] args = new String[st.countTokens() - 1];
try
RunProg rp = (RunProg)this.clone();
rp.iProg = st.nextToken();
for(int j = 0; st.hasMoreTokens(); j++)
     args[j] = st.nextToken();
rp.iArgs = args;
Thread th = new Thread(rp);
th.setName("prog" + i + "=" + program);
th.start();
System.out.println("prog" + i + "=" + program + ", started");
catch(CloneNotSupportedException e)
System.out.println("prog" + i + "=" + program + ", can't start");
i++;
     System.out.println("end of main, activeCount=" + Thread.activeCount());
// next step is to start all others one by one
public void run()
try
Class c = Class.forName(iProg);
Class p[] = new Class[1];
p[0] = String[].class;
Method m = c.getMethod("main", p);
Object o[] = new Object[1];
o[0] = iArgs;
m.invoke(null, o);
catch(ClassNotFoundException e)
System.out.println(iProg + "ClassNotFoundException");
catch(NoSuchMethodException e)
System.out.println(iProg + "NoSuchMethodException");
catch(InvocationTargetException e)
System.out.println(iProg + "NoSuchMethodException");
catch(IllegalAccessException e)
System.out.println(iProg + "NoSuchMethodException");
System.out.println(Thread.currentThread().getName() + ", ended");
System.out.println("exit run, activeCount=" + Thread.activeCount());
// setup SecurityManager to disable method System.exit()
public RunProg()
     SecurityManager sm = new mySecurityManager();
     System.setSecurityManager(sm);
// inner-class to disable method System.exit()
protected class mySecurityManager extends SecurityManager
     public void checkExit(int status)
          super.checkExit(status);
          Thread.currentThread().stop();
          throw new SecurityException();
* inner-class to analyze StringTokenizer. This class is enhanced to check double Quotation marks
protected class StringTokenizer implements Enumeration
private int currentPosition;
private int maxPosition;
private String str;
private String delimiters;
private boolean retTokens;
* Constructs a string tokenizer for the specified string. All
* characters in the <code>delim</code> argument are the delimiters
* for separating tokens.
* <p>
* If the <code>returnTokens</code> flag is <code>true</code>, then
* the delimiter characters are also returned as tokens. Each
* delimiter is returned as a string of length one. If the flag is
* <code>false</code>, the delimiter characters are skipped and only
* serve as separators between tokens.
* @param str a string to be parsed.
* @param delim the delimiters.
* @param returnTokens flag indicating whether to return the delimiters
* as tokens.
public StringTokenizer(String str, String delim, boolean returnTokens)
currentPosition = 0;
this.str = str;
maxPosition = str.length();
delimiters = delim;
retTokens = returnTokens;
* Constructs a string tokenizer for the specified string. The
* characters in the <code>delim</code> argument are the delimiters
* for separating tokens. Delimiter characters themselves will not
* be treated as tokens.
* @param str a string to be parsed.
* @param delim the delimiters.
public StringTokenizer(String str, String delim)
this(str, delim, false);
* Constructs a string tokenizer for the specified string. The
* tokenizer uses the default delimiter set, which is
* <code>"\t\n\r\f"</code>: the space character, the tab
* character, the newline character, the carriage-return character,
* and the form-feed character. Delimiter characters themselves will
* not be treated as tokens.
* @param str a string to be parsed.
public StringTokenizer(String str)
this(str, " \t\n\r\f", false);
* Skips delimiters.
protected void skipDelimiters()
while(!retTokens &&
(currentPosition < maxPosition) &&
(delimiters.indexOf(str.charAt(currentPosition)) >= 0))
currentPosition++;
* Tests if there are more tokens available from this tokenizer's string.
* If this method returns <tt>true</tt>, then a subsequent call to
* <tt>nextToken</tt> with no argument will successfully return a token.
* @return <code>true</code> if and only if there is at least one token
* in the string after the current position; <code>false</code>
* otherwise.
public boolean hasMoreTokens()
skipDelimiters();
return(currentPosition < maxPosition);
* Returns the next token from this string tokenizer.
* @return the next token from this string tokenizer.
* @exception NoSuchElementException if there are no more tokens in this
* tokenizer's string.
public String nextToken()
skipDelimiters();
if(currentPosition >= maxPosition)
throw new NoSuchElementException();
int start = currentPosition;
boolean inQuotation = false;
while((currentPosition < maxPosition) &&
(delimiters.indexOf(str.charAt(currentPosition)) < 0 || inQuotation))
if(str.charAt(currentPosition) == '"')
inQuotation = !inQuotation;
currentPosition++;
if(retTokens && (start == currentPosition) &&
(delimiters.indexOf(str.charAt(currentPosition)) >= 0))
currentPosition++;
String s = str.substring(start, currentPosition);
if(s.charAt(0) == '"')
s = s.substring(1);
if(s.charAt(s.length() - 1) == '"')
s = s.substring(0, s.length() - 1);
return s;
* Returns the next token in this string tokenizer's string. First,
* the set of characters considered to be delimiters by this
* <tt>StringTokenizer</tt> object is changed to be the characters in
* the string <tt>delim</tt>. Then the next token in the string
* after the current position is returned. The current position is
* advanced beyond the recognized token. The new delimiter set
* remains the default after this call.
* @param delim the new delimiters.
* @return the next token, after switching to the new delimiter set.
* @exception NoSuchElementException if there are no more tokens in this
* tokenizer's string.
public String nextToken(String delim)
delimiters = delim;
return nextToken();
* Returns the same value as the <code>hasMoreTokens</code>
* method. It exists so that this class can implement the
* <code>Enumeration</code> interface.
* @return <code>true</code> if there are more tokens;
* <code>false</code> otherwise.
* @see java.util.Enumeration
* @see java.util.StringTokenizer#hasMoreTokens()
public boolean hasMoreElements()
return hasMoreTokens();
* Returns the same value as the <code>nextToken</code> method,
* except that its declared return value is <code>Object</code> rather than
* <code>String</code>. It exists so that this class can implement the
* <code>Enumeration</code> interface.
* @return the next token in the string.
* @exception NoSuchElementException if there are no more tokens in this
* tokenizer's string.
* @see java.util.Enumeration
* @see java.util.StringTokenizer#nextToken()
public Object nextElement()
return nextToken();
* Calculates the number of times that this tokenizer's
* <code>nextToken</code> method can be called before it generates an
* exception. The current position is not advanced.
* @return the number of tokens remaining in the string using the current
* delimiter set.
* @see java.util.StringTokenizer#nextToken()
public int countTokens()
int count = 0;
int currpos = currentPosition;
while(currpos < maxPosition)
* This is just skipDelimiters(); but it does not affect
* currentPosition.
while(!retTokens &&
(currpos < maxPosition) &&
(delimiters.indexOf(str.charAt(currpos)) >= 0))
currpos++;
if(currpos >= maxPosition)
break;
int start = currpos;
boolean inQuotation = false;
while((currpos < maxPosition) &&
(delimiters.indexOf(str.charAt(currpos)) < 0 || inQuotation))
if(str.charAt(currpos) == '"')
inQuotation = !inQuotation;
currpos++;
if(retTokens && (start == currpos) &&
(delimiters.indexOf(str.charAt(currpos)) >= 0))
currpos++;
count++;
return count;
</pre>
RunProg.properties like this:
Prog1=GetEnv 47838 837489 892374 839274
Prog0=GetEnv "djkfds dfkljsd" dsklfj

Running SUN JRE and Microsoft VM in InternetExplorer on the same machine

Our product needs at least Java 1.3 to run.
One of our customers needs to run old applets which for some reason I don't know need the microsoft VM.
Is there a way to install/run both VMs on the same machine?
Udo

Can they be installed - yes.
But your code will not run in the MS VM. And if their applets won't run in your VM that means there will be two VMs running as two separate processes. So the applets will not be interacting with your code directly.

Can I run 64 bit LabVIEW and 32 bit LabVIEW on the same machine?

If I have a 64 bit OS (Windows 7 64 bit or Server 2008 64 bit) can I install and run 32 and 64 bit LabVIEW on the same machine?
John

LabVIEW 64-Bit vs. 32-Bit Applications FAQ
Q. Can I have both LabVIEW 32-bit and LabVIEW 64-bit installed on the same 64-bit machine?
A. Yes.
The FAQ will likely answer other questions you have regarding the restrictions and issues you will have with having both versions and compiling in one vs the other.

Run DW CS4 and DW CS5.5 update on the same machine?

Is it possible to run DW CS4 and DW CS 5.5 (as an update of the DW CS 4) on the same machine? Due to the fact that ADDT doesn't exist anymore and we still have some projects needed to be maintained on ADDT, DW CS 4 should still be usable on the same Mac.

Yes, each upgrade installs into its own folder.
Just don't try and run them at the same time.
Many people keep half a dozen versions (upgrades of each other) on their hard drive since hard drives are so spacious these days.

Running 2 java apps means 2 JVM instances ?

For each running Java application I start on my desktop do I get a seperate instance of the JVM ? If so that seems like such a waste ...

Yes. If you find this wasteful, though, you could write a Java application that runs your applications in a single JVM, in separate threads, but that would be violating the first two rules of optimization:
1. Don't do it.
2. Don't do it yet.
Those rules are there to remind you not to try to optimize a situation until you know that it needs to be optimized and until you know how to optimize it.

Running multiple java-apps in single JVM?

We have about 125 Citrix clients running on 5 Citrix Servers. We are investigating a new very big development project which will cover about 10 main projects with 15 Applications each. The complete project will be written in Java.
Basically, each module will have it's own JVM. BUt, when each client runs a couple of modules, the servers will surely run out of memory...
I searched for way's to run different modules within 1 single JVM but it seems to be 'not done', because of 'System.exit()', 'Static Variable' probs to name only 2.
Any idea's on how to implement this?
thanks.

thanks for the reply.
Yes, I assume the server will run out of memory.
1) Our citrix servers are consuming about 3/4th of their 4Gb memory capacity without any java_application running.
2) Each of our 5 Citrix servers has 25 users active
3) Each JVM takes about 20mb memory
4) Each user will run at least 3 app's simultaneously
Abouve results in 3*20=60Mb / user * 25= 1,5Gb memory extra needed.
Can you give me an example of a Thread.sleep(60000) test_pgm?
and/or an example for a "classloader" program to launch each app in its ow sandbox (in same JVM)?
(eventually a link to get more info on this)
thanks

Can you run Logic Pro 8 and Logic Pro X on the same machine?

Hello all!
Congratulations to us on the release of the new Logic Pro!
I am still running Logic Pro 8 (and was waiting for X to come out since I knew it wasn't too far off) but am concerned over the loss of 32-bit plug-ins with Logic Pro X (the wrapping of my old VST plug-ins alone hurts!). I've heard that installing Logic Pro X doesn't in any way gimp Logic Pro 9's usage, but can someone confirm whether or not Logic Pro X and Logic Pro 8 can operate in harmony on the same Mac?
As a bonus, is there any reason to believe that Apple would disable earlier versions of Logic Pro (such as version 8) from running on Mavericks?
I am planning my Logic Pro and Mac OS migrations! Thanks!!

Try here:
https://discussions.apple.com/community/professional_applications/logic_pro
This forum is FCP X.
Al

Is it possible to run VLM and lmtools on the same machine

hi together ... is it possible to run VLM and lmtools on the same machine without any problems?
the running system will be Windows Server 2008 R2 x64! maybe we will install the license server on the virtual server.

Hi SvenNittmann,
in general, it should be possible to run both tools (VLM and lmtools for FlexNet) on the same machine. But I wouldn't recommend you this way, because NI VLM is also build on top of FlexNet and sometimes you will receive ugly problems with the installation of both tools on the same PC. It is possible to use VLM in a virtual machine without any problems or restrictions. NI provides information about the usage of VLM in a virtual machine, like you can see here:
Volume License Manager on a Virtual Machine - National Instruments
http://digital.ni.com/public.nsf/allkb/5730FDDC97F9157E8625755F00749CFF?OpenDocument
I also use VLM in a virtual machine and I could recommend you the same solution.
Regards, Stephan

What ways of communication between two java apps you know?

Hi all
Lame (but not for me) question.
I have two java applications (first is web-app unning on server (tomcat or JBoss) and second is a standalone java app). Both are running on different JVM and both have to communicate with each other quite often - but mainly: the second one is going to pass results of its work to the first one.
What way of communication would you suggest?
Ps. I'm free to choose frameworks and overall architecture.
Regards
Grzesiek

YoungWinston wrote:
Blimey. That's a question and a half; and the answer will likely depend on what you need to do/send.
For straight messaging, there's JMS, but for more esoteric stuff you might want to involve a database, so you may want to look at JDBC (or even something like Hibernate). EJBs generally use servlets, or there's also straight HTTP, even raw sockets.
I suspect to need to rein in your question a bit and come up with some specifics.
Winston
Edited by: YoungWinston on Jan 13, 2011 5:26 PM
Too slow, as usual :-)So:
Blimey. That's a question and a half; and the answer will likely depend on what you need to do/send.Plain text, just statements ;)
For straight messaging, there's JMS, but for more esoteric stuff you might want to involve a database, so you may want to look at JDBC (or even something like Hibernate).Yes, JMS is what might solve my problem. Even if there will be any database(?), the only ones I would be considering are H2, Derby, HSQLDB.
I suspect to need to rein in your question a bit and come up with some specificsA little more details? Ok....
Firstly, ordinary user via web app creates text file, and when it's ready - starts second app in separate JVM (separate JVM is needed due to risk of OutOfMemoryError or any other crashes).
Second app (standalone) is going to process this file (it might take hours/days/weeks) and inform web-app about his progress (about 5 messages per minute).
Of course all those messages are going to be saved in log file/ database (log file should be easier way to go).
Note that many standalone instances of second app are going to be run simultaneously (I think that this is the place to use some database - to store info about all instances: whether they finished successfully or not: eg. due to some crashes)
Thanks for you time and effort
All of You helped me already ;)

Running multiple java apps simultaneously, each using a different jre.

I have a situation where I have 3 or 4 applications (and one applet) that were built over time, each with a different version of the jdk (ranging from 1.2.2.005 to 1.3.2). I need to know of a way (and it must exist) to run each of these applications on the same machine, and at runtime, have each application (or applet) run with its respective version of the jre. Certainly, one could change some source code and make all programs compatible with a particular jre, but that doesn't solve my problem if a new app is built with a new version of the jdk down the road. Currently, each runs fine by themselves, but if I try to run them together as different processes, some won't do anything because the default jre may not be what it needs. Would the Java Plug-in software have a role to play in this? Is there a way to specify (link) which application should use which jre?
P.S. These applications (right now) don't have to interact or interface in any way. I just need to have them all running as separate processes on the same machine and be able to jump from one to the other.

However ... if you have the programs running in Java1.x, I
wouldn't recommend to let it run under Java 1.y; atleast
not without thorough testing.I do it all the time and have not had a problem. I'm
currently using JDK 1.4 beta 3 and I regularly run a
Java application written with JDK 1.1.
It sounds like the programs you are running are
relying on behavior that is not guaranteed. If that
behavior changes in a later version, it can break your
program. Program to the contracts provided by other
classes and packages, and you should have few or no
problems.I guess you are right. Maybe you can help me with the following problem (this is off this topic, I know): I have Swing JDK 1.2 and Swing from JDK 1.3. I have to register keys on components.
In JDK 1.2 I can use registerKeyBoardAction, in JDK 1.3 I have to use input maps and action maps. Both solutions only work with certain JDK. What I did was writing code which detects the java version and takes the appropriate action to register the keys. To make the thing compile in 1.2, I have to use reflection for the input/action map methods, because they are only available in 1.3.
Any idea how to solve this more elegantly ?

Running multiple java apps simultaneously, using different versions of jre.

I have a situation where I have 3 or 4 applications (and one applet) that were built over time, each with a different version of the jdk (ranging from 1.2.2.005 to 1.3.2). I need to know of a way (and it must exist) to run each of these applications on the same machine, and at runtime, have each application (or applet) run with its respective version of the jre. Certainly, one could change some source code and make all programs compatible with a particular jre, but that doesn't solve my problem if a new app is built with a new version of the jdk down the road. Currently, each runs fine by themselves, but if I try to run them together as different processes, some won't do anything because the default jre may not be what it needs. Would the Java Plug-in software have a role to play in this? Is there a way to specify (link) which application should use which jre?
P.S. These applications (right now) don't have to interact or interface in any way. I just need to have them all running as separate processes on the same machine and be able to jump from one to the other.

Write a batch file that sets the environment properly and restores it afterwards, here is a sample batch file we use which switches to IBM's JRE to run an app:
OLDPATH=$PATH
PATH=$PATH:"/usr/local/java/IBMJava2-13/jre/bin"
OLDCP=$CLASSPATH
CLASSPATH="/usr/local/java/IBMJava2-13/jre/lib/rt.jar:."
OLDHOME=$JAVA_HOME
JAVA_HOME="/usr/local/java/IBMJava2-13/jre"
# put the command to execute your program here
java -jar app.jar
PATH=$OLDPATH
CLASSPATH=$CLASSPATH
JAVA_HOME=$JAVA_HOME
This is for Linux, but it should be possible to write one for Windows too.

How to make a shortcut to run my Java app in Windows?

Hiya, Coders :-)
I am an absolute beginner.
I have copied a little window program from "Java 2 in easy steps".
I run it from the command line and a little window pops up.
I cannot find a way to start the app without the command prompt.
How can I make a shortcut to start it?
Julian (-_-)

Hiya, Coders ;-)
As it happens, I have a game from UJ Software: "Shisen for Java".
It has a shortcut, of course.
Here are all its details just in case it helps ...
The game folder is here:
C:\Program Files\UJ Software\Shisen for Java\jShisen.jar
Contents of the installed shortcut ...
General:
Type of file: Shortcut
Opens with: Java(TM) Platform SE binary
Location: C:\Documents and Settings\Julian Bury\Start Menu\Games
Shortcut:
Target Type: Executable Jar File
Target location: Shisen for Java
Target: "C:\Program Files\UJ Software\Shisen for Java\jShisen.jar"
Start in: "C:\Program Files\UJ Software\Shisen for Java\"
Run: Normal window
I don't suppose this will help.
It strikes me that nobody knows for certain how to run a java app!
I have two beginner's books, neither of which mentions anything beyond the command prompt.
Tricks to minimize the console window are just not professional!
The solution must be written authoritatively somewhere ...
has anyone seen it, please?
Increasingly disturbed ...
Julian *(-_-)*

Running Sun App Server 7 and 8 on the same box

Hello,
Are there any known issues with running Sun App Server 7 and 8 in the same host box ? Currently I am encountering some class not found exceptions with Sun App Server 8 . Sun App Server 7 runs just fine.
Thanks,
Aswin.

It's not advisable to run separate installations of
ColdFusion 7 and ColdFusion 8 single server on the same machine the
re are several services that will try to use the same ports.
However, you can install ColdFusion Enterprise using the
multi-server configuration and then deploy the J2EE versions of
ColdFusion to JRun. You can change the JVM that each instance uses
(we recommend the latest 1.4 for CF7 and the latest 1.6 for CF8),
and everything should run fine.
ColdFusion itself is essentially just a J2EE application, the
J2EE server itself is JRun 4. So the specific answer to your
question is "don't install 2 copies of JRun 4 to the same machine".
But yes, it's 100% possible, I'm running this configuration in my
own development environment.

I'm running Pages version 5.2 on a Desktop Mac version 10.9.2. with the Pages app open how do I use the Time Machine to go back five hours to see the work?

I'm running Pages version 5.2 on a Desktop Mac version 10.9.2. With the Pages app open how do I use the Time Machine to go back five hours to see my page? Can I access Time Machine within an app like Pages? How do I enter Time Machine within the application? It always takes me to the Finder. I apolgise for the mumbo jumbo. I simply do not know how to use Time Machine. It makes sense when I follow the Tutorial but then I lose it.

OK. You've kind of skipped over the reason why you want to go back five hours, but my assumption would be that you've made changes to a Pages file that you want to revert.
There are two ways to tackle this. From Pages itself, open the current version of your document, and from the File menu, click Revert To, and Browse All Versions. You'll then be in the Time Machine interface for that file, and can browse back to the version you want.
Or, outside of Pages, you can select the file (or the folder it was originally in, if you've since deleted it) and enter Time Machine from the TM menu (it sounds like you've already tried this?)
best
Matt

Run two java apps in separate jvm's on the same machine?

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