Go to Window &amp;#8594; Preferences &amp;#8594; Java &amp;#8594; Installed JREs. Select the JRE you&#39;re using, click Edit, and there will be a line for Default VM Arguments which will apply to every execution. For instance, I use this on OS X to hide the icon from the dock, increase max memory and turn on assertions:

    -Xmx512m -ea -Djava.awt.headless=true

Yes, right click the project. Click `Run as` then `Run Configurations`. You can change the parameters passed to the JVM in the `Arguments` tab in the `VM Arguments` box.

That configuration can then be used as the default when running the project.

As far as I know there is no option to create global configuration for java applications. You always create a duplicate of the configuration. 


![enter image description here][1]

Also, if you are using PDE (for plugin development), you can create target platform using windows -&gt; Preferences -&gt; Plug-in development -&gt; Target Platform. Edit has options for program/vm arguments. 

Hope this helps

  [1]: http://i.stack.imgur.com/A61l7.jpg

I already created a txt file using python with a few lines of text that will be read by a simple program. However, I am having some trouble reopening the file and writing additional lines in the file in a later part of the program. (The lines will be written from user input obtained later on.) 

    with open(&#39;file.txt&#39;, &#39;w&#39;) as file:
        file.write(&#39;input&#39;)

This is assuming that &#39;file.txt&#39; has been opened before and written in. In opening this a second time however, with the code that I currently have, I have to erase everything that was written before and rewrite the new line. Is there a way to prevent this from happening (and possibly cut down on the excessive code of opening the file again)?

how to add lines to existing file using python

I came across a class using Integer variables to capture size to be used in a for loop. Is this good practice or should we use the int primitive data type?

    Integer size = something.getFields().size();
    for (Integer j = 0; j &lt; size - 1; ++j) 

Using int vs Integer

Is there a way to specify default JVM arguments when I&#39;m running my code from eclipse, rather than specifying the same ones over and over for each run/debug/etc configuration?

How can I specify the default JVM arguments for programs I run from eclipse?

<p>Is there a way to specify default JVM arguments when I'm running my code from eclipse, rather than specifying the same ones over and over for each run/debug/etc configuration?</p>


I have the following class and interface:

    public class BasicObject{...}
    public interface CodeObject{...}

I want to create a method in which the argument needs to be of type BasicObject and implements CodeObject. I tried the following code but it doesn&#39;t guarantee clazz to be a class that implements CodeObject.

    myMethod(Class&lt;? extends BasicObject&gt; clazz){...}

I want to do something like this but it doesn&#39;t compile:

    myMethod(Class&lt;? extends BasicObject implements CodeObject&gt; clazz){...}

Method argument extends class implements interface

I have Date in this format  (2012-11-17T00:00:00.000-05:00). I need to convert the date into this format mm/yyyy.

I tried this way, but I am getting this Exception.

    Exception in thread &quot;main&quot; java.lang.IllegalArgumentException: Cannot format given Object as a Date
    	at java.text.DateFormat.format(Unknown Source)
    	at java.text.Format.format(Unknown Source)
    	at DateParser.main(DateParser.java:14)

Please see my code below: 

```java
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateParser {    
  public static void main(String args[]) {   
    String MonthYear = null;    
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat(&quot;mm/yyyy&quot;);    
    String dateformat = &quot;2012-11-17T00:00:00.000-05:00&quot;;
    MonthYear = simpleDateFormat.format(dateformat);    
    System.out.println(MonthYear);    
  }    
}
```

Java : Cannot format given Object as a Date

I&#39;m a beginner in Java and am trying to run my code using IntelliJ that I just installed as my IDE with JDK 1.7.  The following piece of code keeps does not even compile and keeps giving me the error:

    Error: Could not find or load main class libTest

##Code

    import java.lang.Integer;
    import java.lang.String;
    import java.lang.System;
    import java.util.*;

    class book {

        private String name = &quot;trial&quot;;
        private int bookCode=1;
        private int issued=0;

         public void Issue(){
             if(issued==0) {
                 issued=1;
                 System.out.println(&quot;You have succesfully issued the book&quot;);
             }
             else {
                 System.out.println(&quot;The book is already issued. Please contact the librarian for further details&quot;);
             }
        }

        public int checkCode() {
            return bookCode;
        }

        String readName() {
            return name;
        }

        public void setName(String newName){
            name=newName;
        }

        public void setBookCode(int newCode){
            bookCode=newCode;
        }
    }

    class library {
        private ArrayList books=new ArrayList();

        public void getList(){
            for(int bk:books){
                String bName=books(bk).readName();
                System.out.println((bk+1)+&quot;)  &quot;+bName);
            }
        }
    }

    public class libTest{
        public static void main(String[] args){
            library newLib= new library();
            System.out.println(&quot;code working&quot;);
       }
    }


Is there any change that i have to make in the compiler settings?? Or is it the code.

Error: Could not find or load main class in intelliJ IDE

Yes, this is an old topic, but I still have some confusions.

In Java, people say:

1. ArrayList is faster than LinkedList if I randomly access its elements. I think random access means &quot;give me the nth element&quot;. Why ArrayList is faster?

2. LinkedList is faster than ArrayList for deletion. I understand this one. ArrayList&#39;s slower since the internal backing-up array needs to be reallocated. A code explanation:

		List&lt;String&gt; list = new ArrayList&lt;String&gt;();
		list.add(&quot;a&quot;);
		list.add(&quot;b&quot;);
		list.add(&quot;c&quot;);
		list.remove(&quot;b&quot;);
		System.out.println(list.get(1)); //output &quot;c&quot;

3. LinkedList is faster than ArrayList for insertion. What does insertion mean here? If it means to move some elements back and then put the element in the middle empty spot, ArrayList should be slower than LinkedList. If insertion only means an add(Object) operation, how could this be slow? 


Performance differences between ArrayList and LinkedList

In case of the [Proxy Design Pattern][1], What is the difference between [JDK&#39;s Dynamic Proxy][2] and third party dynamic code generation API s such as [CGLib][3]? 

What is the difference between using both the approaches and when should one prefer one over another?


  [1]: http://en.wikipedia.org/wiki/Proxy_pattern
  [2]: http://docs.oracle.com/javase/7/docs/api/java/lang/reflect/Proxy.html
  [3]: http://cglib.sourceforge.net/

What is the difference between JDK dynamic proxy and CGLib?

I am using the Git plugin for Eclipse. I have several authors and committers which are displayed when I start typing in those fields.

How can I provide changes to this list, or remove some author or committer?

Also I want to set my default author and committer which will be displayed by default.

![Enter image description here][1]

  [1]: http://i.stack.imgur.com/Nc6l3.png


How do I change the default author and committer in the Eclipse Git plugin?

I&#39;ve installed eclipse gradle plugin from here 

http://kaczanowscy.pl/tomek/2010-03/gradle-ide-integration-eclipse-plugin

Is there a simple way to import into eclipse gradle project using gui, not doing stuff

described here: http://gradle.org/docs/current/userguide/eclipse_plugin.html

?

Import existing Gradle Git project into Eclipse

I am using LG-P500. When I try to select it in the &#39;Android device chooser&#39;, Eclipse recognizes the phone but not the target. It says target &quot;unknown&quot;. Because of this problem, I can&#39;t choose the phone as the Android device.

How can I get Eclipse to recognize the target?

Eclipse - Target &quot;unknown&quot; in Android device chooser

The error is as above. I have what should be all the necessary files include in the eclipse project:

    /usr/include/c++/4.6
    /usr/include
    /usr/include/linux
    /usr/local/include
etc. 

I tried `std::cout` and `using namespace std;` `cout` but it still says unresolved. 

I have imported `iostream` and `cstdlib`.

Also, I&#39;m on Ubuntu 12.04 with eclipse 3.7.2.

Code snippet:

    #include &lt;cstdio&gt;
    #include &lt;cstdlib&gt;
    #include &lt;cstring&gt;
    #include &lt;iostream&gt;
    #include &quot;XPLMDisplay.h&quot;
    #include &quot;XPLMGraphics.h&quot;

    int XPluginStart(char * outName,  char * outSig,  char * outDesc) {
        /* ... */
        std::cout &lt;&lt; &quot;test&quot; &lt;&lt; std::endl;
        /* ... */
    }

using namespace std;


----------


UPDATE: I had created the eclipse project from existing code. Creating a new c++ project fixes it. I&#39;ll accept an answer that explains what setting in the existing project could cause this (so I don&#39;t have to cut &amp; paste all my projects).

Eclipse CDT: Symbol &#39;cout&#39; could not be resolved

I&#39;m working on a simple JSP/Servlet/Tomcat webapp for my class. The professor asked us to use a folder structure that is slightly different than the default dynamic web project structure. Rather than using the webcontent folder he wants all of our source code under src/main/java and src/main/webapp.

When I run the app my welcome file displays fine, but when I try to access my servlets I get:

     Http 500 SEVERE: Allocate exception for servlet InitDb
java.lang.ClassNotFoundException. I&#39;m pretty sure it&#39;s a build path error. I have final/src on the build path but I am receiving the warning  

    &quot;Cannot nest &#39;final/src/main/webapp/WEB-INF/classes&#39; inside &#39;final/src&#39;. To enable the    nesting exclude &#39;main/&#39; from &#39;final/src&#39;

![enter image description here][1]


  [1]: http://i.stack.imgur.com/WbiGC.jpg

I have this in my deployment assembly: 

    &lt;wb-resource deploy-path=&quot;/&quot; source-path=&quot;/src/main/webapp&quot; tag=&quot;defaultRootSource&quot;/&gt; 

When I exclude main/ the warning goes away, but it doesn&#39;t fix the problem. I would appreciate any advice. Thanks. 

Eclipse Build Path Nesting Errors

For Sun/Oracle&#39;s JVM, I&#39;ve read that the GC algo divides new generation into one Eden region and two survivor regions. What I&#39;m wondering about is, why two survivor regions and not just one? The algo can keep ping-ponging between Eden and just one survivor region (the way it currently does between two survivor regions); or are there any shortcomings to this approach?

Java GC: why two survivor regions?

Htop on my linux machine shows many &quot;processes&quot; after launching one java program/JVM. I do understand that the JVM runs multiple
threads (for the actual program, for garbage collection, etc). 

But how come htop lists them as multiple processes with different pids. What exactly are those processes?

Htop showing multiple java processes with different pids

I am trying to run a .jar file that was created successfully in Netbeans and I am receiving the following error:

&gt; Error occurred during initialization of VM java.lang.Error: 
&gt; Properties init: Could not determine current working directory. at 
&gt; java.lang.System.initProperties(Native Method) at 
&gt; java.lang.System.initializeSystemClass(System.java:1070) 

The command that I type to run the .jar is 

    java -jar &quot;/path to the dist forlder/EOPPrototype.jar&quot;

My classpath is as follows:

    CLASSPATH=/opt/netbeans-7.1.2/ide/modules/ext/mysql-connector-java-5.1.13-     bin.jar:/h/USERS/local/pagola/NetBeansProjects/mylib/dist/mylib.jar:/h/USERS/local/pagola/NetBeansProjects/EOPPrototype/build/classes:.

What am i missing?


Cannot determine current directory

What does the HotSpot JVM flag `-XX:+UseCompressedOops` do and when should I use it? What sort of performance and memory-usage differences will I see when using it on a 64-bit Java instance (vs. not using it)? 

What does the UseCompressedOops JVM flag do and when should I use it?

I was trying to find out the difference between Apache Tomcat variables - `CATALINA_OPTS` and `JAVA_OPTS` in [SO][1] and surprised to see that there is no question/answer posted here yet.  So I thought of sharing it here (with answer) after finding out the difference.  Check the answer/difference below.

**NOTE:** At the time of this posting, we&#39;re running Apache Tomcat v6.0.10 with JDK 6u32 on CentOS5 64-bit arch.

  [1]: http://stackoverflow.com &quot;StackOverflow&quot;

Content Type	Original Author	Original Content on Stackoverflow
Question	Thomas Johnson	View Question on Stackoverflow
Solution 1 - Java	Alice Young	View Answer on Stackoverflow
Solution 2 - Java	Jivings	View Answer on Stackoverflow
Solution 3 - Java	Ravi	View Answer on Stackoverflow

How can I specify the default JVM arguments for programs I run from eclipse?

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

Solution 3 - Java

Using int vs Integer

how to add lines to existing file using python

Attributions