You can setup `_JAVA_OPTIONS` instead of `JAVA_OPTS`. This should work without `$_JAVA_OPTIONS`.

I don&#39;t know of any JVM that actually checks the `JAVA_OPTS` environment variable.  Usually this is used in scripts which launch the JVM and they usually just add it to the `java` command-line.

The key thing to understand here is that arguments to `java` that come *before* the `-jar analyse.jar` bit will only affect the JVM and *won&#39;t* be passed along to your program.  So, modifying the `java` line in your script to:

    java $JAVA_OPTS -jar analyse.jar $*

Should &quot;just work&quot;.

My web server would be overloaded quickly if all the work were done there.  I&#39;m going to stand up a second server behind it, to process data.

What&#39;s the advantage of EJB over RMI, or vice versa?  

What about web services (SOAP, REST)?



Web Services vs EJB vs RMI, advantages and disadvantages?

Is there a shortcut in NetBeans to highlight a block of code and comment/uncomment it?

Comment/uncomment a block of code in NetBeans shortcut

In a shell script, I have set the JAVA_OPTS environment variable (to enable remote debugging and increase memory), and then I execute the jar file as follows:

    export JAVA_OPTS=&quot;-Xdebug -Xrunjdwp:transport=dt_socket,address=8001,server=y,suspend=n -Xms512m -Xmx512m&quot;
    java -jar analyse.jar $*

But it seems there is no effect of the JAVA_OPTS env variable as I cannot connect to remote-debugging and I see no change in memory for the JVM.

What could be the problem?

PS: I cannot use those settings in the `java -jar analyse.jar $*` command because I process command line arguments in the application. 

Running java with JAVA_OPTS env variable has no effect

In a shell script, I have set the JAVA_OPTS environment variable (to enable remote debugging and increase memory), and then I execute the jar file as follows:
<pre><code class="hljs language-ini">export JAVA_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,address=8001,server=y,suspend=n -Xms512m -Xmx512m"
java -jar analyse.jar $*
</code></pre>
But it seems there is no effect of the JAVA_OPTS env variable as I cannot connect to remote-debugging and I see no change in memory for the JVM.
What could be the problem?
PS: I cannot use those settings in the <code>java -jar analyse.jar $*</code> command because I process command line arguments in the application.

I have a problem with a simple `@OneToMany` mapping between a parent and a child entity. All works well, only that child records are not deleted when I remove them from the collection.

The parent:

    @Entity
    public class Parent {
        @Id
        @Column(name = &quot;ID&quot;)
        private Long id;
    
        @OneToMany(cascade = {CascadeType.ALL}, mappedBy = &quot;parent&quot;)
        private Set&lt;Child&gt; childs = new HashSet&lt;Child&gt;();
    
     ...
    }

The child:

    @Entity
    public class Child {
        @Id
        @Column(name = &quot;ID&quot;)
        private Long id;
    
        @ManyToOne(cascade = CascadeType.ALL)
        @JoinColumn(name=&quot;PARENTID&quot;, nullable = false)
        private Parent parent;
    
      ...
    }

If I now delete and child from the childs Set, it does not get deleted from the database. I tried nullifying the `child.parent` reference, but that did not work either.

The entities are used in a web application, the delete happens as part of an Ajax request. I don&#39;t have a list of deleted childs when the save button is pressed, so I can&#39;t delete them implicitly. 



JPA OneToMany not deleting child

I have a j2ee application using hibernate with annotation. How do I annotate the Id field in my pojo class to set it as auto increment or auto generated. and in adding the bean do I leave that field in my bean null?

Hibernate Auto Increment ID

&gt; **Possible Duplicate:**  
&gt; [How do I create an .exe for a Java program?](https://stackoverflow.com/questions/516399/how-do-i-create-an-exe-for-a-java-program)  

&lt;!-- End of automatically inserted text --&gt;

I&#39;ve just made a simple program with Eclipse and I want to compile it into an executable, but simply can&#39;t seem to find out how to do it.

Compiling a java program into an executable

For instance, `%11.2lf` in C++ becomes `%11.2f` in Java.
How about for long format?

C++ Equivalent of %ld in Java for String.format()

Take the following:

	public Class&lt;List&lt;String&gt;&gt; getObjectType() {
		// what can I return here?
	}

What class literal expression can I return from this method which will satisfy the generics and compile? `List.class` won&#39;t compile, and neither will `List.&lt;String&gt;class`.

If you&#39;re wondering &quot;why&quot;, I&#39;m writing an implementation of Spring&#39;s `FactoryBean&lt;List&lt;String&gt;&gt;`, which requires me to implement `Class&lt;List&lt;String&gt;&gt; getObjectType()`. However, this is *not* a Spring question.

**edit:** My plaintive cries have been heard by the powers that be at SpringSource, and so Spring 3.0.1 will have the return type of `getObjectType()` changed to `Class&lt;?&gt;`, which neatly avoids the problem.

How to create a class literal of a known type: Class&lt;List&lt;String&gt;&gt;

I have a whole bunch of tests on variables in a bash (3.00) shell script where if the variable is not set, then it assigns a default, e.g.:

    if [ -z &quot;${VARIABLE}&quot; ]; then 
        FOO=&#39;default&#39;
    else 
        FOO=${VARIABLE}
    fi

I seem to recall there&#39;s some syntax to doing this in one line, something resembling a ternary operator, e.g.:

    FOO=${ ${VARIABLE} : &#39;default&#39; }

(though I know that won&#39;t work...)

Am I crazy, or does something like that exist?



Assigning default values to shell variables with a single command in bash

I have two directories with the same list of files. I need to compare all the files present in both the directories using the `diff` command. Is there a simple command line option to do it, or do I have to write a shell script to get the file listing and then iterate through them?

Diff files present in two different directories

I need to execute some make rules conditionally, only if the Python installed is greater than a certain version (say 2.5).

I thought I could do something like executing:

    python -c &#39;import sys; print int(sys.version_info &gt;= (2,5))&#39;

and then using the output (&#39;1&#39; if ok, &#39;0&#39; otherwise) in a `ifeq` make statement.

In a simple bash shell script it&#39;s just:

    MY_VAR=`python -c &#39;import sys; print int(sys.version_info &gt;= (2,5))&#39;`

but that doesn&#39;t work in a Makefile.

Any suggestions? I could use any other sensible workaround to achieve this.

How to assign the output of a command to a Makefile variable

I&#39;m using Python with `-c` to execute a one-liner loop, i.e.:

```lang-none
python -c &quot;for r in range(10): print &#39;rob&#39;&quot;
```

This works fine. However, if I import a module before the *for* loop, I get a syntax error:

```lang-none
python -c &quot;import sys; for r in range(10): print &#39;rob&#39;&quot;

  File &quot;&lt;string&gt;&quot;, line 1
    import sys; for r in range(10): print &#39;rob&#39;
              ^
SyntaxError: invalid syntax
```

How can this be fixed?

It&#39;s important to me to have this as a one-liner so that I can include it in a [Makefile][1].

  [1]: https://en.wikipedia.org/wiki/Make_(software)#Makefile






Executing multi-line statements in the one-line command-line

I use the pylons and sqlalchemy. I constantly update the schema files and delete and recreate the database so that new schema can be made. 

Every time I do this by opening the MySql Query Browser and login and delete the database/schema.

**How do I delete the MySQL db/schema thorough linux shell commands in Ubuntu Linux?**

How to delete mysql database through shell command

I really like the remote debugging facilities of the JVM. But I wonder how it works internally.

My assumption: It is done through a JVM feature where the running process is downloading/using the source-code from the attached remote-debugger (like IDE) It knows the line of the current stack-trace and then can jump to the respective IDE breakpoint. The communication of stack-trace and introspection of the application state is then done either through sockets or shared-memory (setting of remote debugger).

Has anybody interesting links/resources on that?



Java remote debugging, how does it work technically?

I have the following boxes:

a) A Windows box with Eclipse CDT,  
b) A Linux box, accessible for me only via SSH.

Both the compiler and the hardware required to build and run my project is only on machine B.

I&#39;d like to work &quot;transparently&quot; from a Windows box on that project using Eclipse CDT and be able to build, run and debug the project remotely from within the IDE.

How do I set up that:

- The building will work? Any simpler solutions than writing a local makefile which would `rsync` the project and then call a remote makefile to initiate the actual build? Does Eclipse managed build have a feature for that?
- The debugging will work?
- Preferably - the Eclipse CDT code indexing will work? Do I have to copy all required header files from machine B to machine A and add them to include path manually?



Work on a remote project with Eclipse via SSH

I have just set up a wi-fi network at home. I have all my files on my desktop computer (192.168.1.56) and want to access localhost over there from another computer (192.168.1.2).

On my desktop I can access localhost through the normal http://localhost. Apache is running on port 80 as usual.

What do I have to do to achieve this? There is documentation on the net but they either don&#39;t work or are too fragmented and confusing to understand.

I think I have to make changes to my apache&#39;s httpd.conf file and the hosts file. Any ideas as to what changes to make?

Accessing localhost (xampp) from another computer over LAN network - how to?

How do people debug websites on mobile devices?

I&#39;d like to be able to manipulate the HTML and CSS similar to using the Inspector in a desktop browser, and debug JavaScript.

How to debug web sites on mobile devices?

I&#39;m trying to get debugging up between PyCharm (on windows host) and a debian virtual host running my django application.  The instructions say to install the egg, add the import, and then invoke a command. I assume these things need to be done on the debian host?

Ok, then, in what file should I put these two lines?

    from pydev import pydevd
    pydevd.settrace(&#39;not.local&#39;, port=21000, stdoutToServer=True, stderrToServer=True)

I tried putting it into the settings.py but got this kind of thing...

    File &quot;/django/conf/__init__.py&quot;, line 87, in __init__
        mod = importlib.import_module(self.SETTINGS_MODULE)
    File &quot;/django/utils/importlib.py&quot;, line 35, in import_module
        __import__(name)
    File &quot;/settings.py&quot;, line 10, in &lt;module&gt;
        pydevd.settrace(&#39;dan.local&#39;, port=21000, stdoutToServer=True, stderrToServer=True)
    File &quot;/pycharm-debug.egg/pydev/pydevd.py&quot;, line 1079, in settrace
        debugger.connect(host, port)
    File &quot;/pycharm-debug.egg/pydev/pydevd.py&quot;, line 241, in connect
        s = StartClient(host, port)
    File &quot;/pycharm-debug.egg/pydev/pydevd_comm.py&quot;, line 362, in StartClient
        sys.exit(1)
    SystemExit: 1

Whilst pycharm just sat there &quot;waiting for connection&quot;

How do I start up remote debugging with PyCharm?

They are algorithms for the young generation garbage collection. 

The second one (UseParNewGC) gets activated automatically with the concurrent tenured generation garbage collection (see [Java Concurrent and Parallel GC][1]) but, is there a difference between the two parallel algorithms?


  [1]: https://stackoverflow.com/questions/220388/java-concurrent-and-parallel-gc

Difference between -XX:+UseParallelGC and -XX:+UseParNewGC

I am running a program that I&#39;ve written in Java in Eclipse. The program has a very deep level of recursion for very large inputs. For smaller inputs the program runs fine however when large inputs are given, I get the following error:

    Exception in thread &quot;main&quot; java.lang.StackOverflowError

Can this be solved by increasing the Java stack size and if so, how do I do this in Eclipse?

&lt;b&gt;Update:&lt;/b&gt;

@Jon Skeet

The code is traversing a parse tree recursively in order to build up a datastructure. So, for example the code will do some work using a node in the parse tree and call itself on the node&#39;s two children, combining their results to give the overall result for the tree.

The total depth of the recursion depends on the size of the parse tree but the code seems to fail (without a larger stack) when the number of recursive calls gets into the 1000s.

Also I&#39;m pretty sure the code isn&#39;t failing because of a bug as it works for small inputs.

Java stack overflow error - how to increase the stack size in Eclipse?

This concerns Intellij from 9 to 11.
In the IDEA window On the bottom right corner I see the current memory usage, typically &quot;224M of 254M&quot; How do I give more memory to Idea so it may read like &quot;224M of 512M&quot; ?

Thank you. 


How to give more memory to IntelliJ Idea 9-11 

Considering the following command line 

    java -Xms128m -Xms256m myapp.jar

Which settings will apply for JVM Minimum memory (`Xms` option) :  128m or 256m ?


Duplicated Java runtime options : what is the order of preference?

I need to run a Java memory intensive application that uses more than 2GB, but I am having problems to increase the heap maximum size. So far, I have tried the following approaches:

- Setting the -Xmx parameter, e.g. -Xmx3000m. This approaches fails at the creation of the JVM. From what I&#39;ve googled, it looks like that -Xmx must be less than 2GB.

- Using the [-XX:+AggressiveHeap option][1]. When I try this approach I get an &#39;Not enough memory&#39; error that tells that the heap size is 1273.4 MB, even though my computer has 8GB of memory.

Is there another approach that I can try to increase the maximum heap size of the JVM? Here&#39;s a summary of the computer specs:

- OS: Windows 7 (64 bit)
- Processor: Intel Core i7 (2.66 GHz)
- Memory: 8 GB
- java -version:

&gt;     java version &quot;1.6.0_18&quot;
&gt;     Java(TM) SE Runtime Environment (build 1.6.0_18-b07)
&gt;     Java HotSpot(TM) Client VM (build 16.0-b13, mixed mode, sharing)


  [1]: http://java.sun.com/docs/hotspot/gc1.4.2/#4.2.2.%20AggressiveHeap|outline

Content Type	Original Author	Original Content on Stackoverflow
Question	Ashika Umanga Umagiliya	View Question on Stackoverflow
Solution 1 - Java	HEX	View Answer on Stackoverflow
Solution 2 - Java	ZoogieZork	View Answer on Stackoverflow

Running java with JAVA_OPTS env variable has no effect

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

Comment/uncomment a block of code in NetBeans shortcut

Web Services vs EJB vs RMI, advantages and disadvantages?

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