java.lang.OutOfMemoryError: PermGen space in Stanbol

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.3.1:compile (default-compile) on project org.apache.stanbol.commons.solr.web: Compilation failure
[ERROR] Failure executing javac, but could not parse the error:
[ERROR]
[ERROR]
[ERROR] The system is out of resources.
[ERROR] Consult the following stack trace for details.
[ERROR] java.lang.OutOfMemoryError: PermGen space
[ERROR] at java.lang.ClassLoader.defineClass1(Native Method)
[ERROR] at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
[ERROR] at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
[ERROR] at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
[ERROR] at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
[ERROR] at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
[ERROR] at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
[ERROR] at java.security.AccessController.doPrivileged(Native Method)
[ERROR] at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
[ERROR] at org.codehaus.plexus.compiler.javac.IsolatedClassLoader.loadClass(IsolatedClassLoader.java:56)
[ERROR] at com.sun.tools.javac.main.Main.compile(Main.java:424)
[ERROR] at com.sun.tools.javac.main.Main.compile(Main.java:353)
[ERROR] at com.sun.tools.javac.main.Main.compile(Main.java:342)
[ERROR] at com.sun.tools.javac.main.Main.compile(Main.java:333)
[ERROR] at com.sun.tools.javac.Main.compile(Main.java:94)
[ERROR] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[ERROR] at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
[ERROR] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[ERROR] at java.lang.reflect.Method.invoke(Method.java:606)
[ERROR] at org.codehaus.plexus.compiler.javac.JavacCompiler.compileInProcess(JavacCompiler.java:549)
[ERROR] at org.codehaus.plexus.compiler.javac.JavacCompiler.compile(JavacCompiler.java:156)
[ERROR] at org.apache.maven.plugin.AbstractCompilerMojo.execute(AbstractCompilerMojo.java:605)
[ERROR] at org.apache.maven.plugin.CompilerMojo.execute(CompilerMojo.java:128)
[ERROR] at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
[ERROR] at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
[ERROR] at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
[ERROR] at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
[ERROR] at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
[ERROR] at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
[ERROR] at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
[ERROR] at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
[ERROR] at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:320)

The solution is,

This error is happening because the JVM parameters for the BigDataLite NoSQL has been not set properly. So you need to add the JVM memory paremeters in ~/.bashrc file. follow the steps,

sudo nano ~/.bashrc

Add the below line in to this file,

export JAVA_OPTS="-Xms128m -Xmx2048m -XX:PermSize=256m -XX:MaxPermSize=2048m"

Finally refresh the ~/.bashrc with the below command,

source ~/.bashrc

Now execute it again.

Best Eclipse plugin

http://www.eclipse.org/Xtext/index.html for any script or build language. This eclispe plugin helps lot.

Why use getters and setters?

• Encapsulation of behavior associated with getting or setting the property - this allows additional functionality (like validation) to be added more easily later.
• Hiding the internal representation of the property while exposing a property using an alternative representation.
• Insulating your public interface from change - allowing the public interface to remain constant while the implementation changes without affecting existing consumers.
• Controlling the lifetime and memory management (disposal) semantics of the property - particularly important in non-managed memory environments (like C++ or Objective-C).
• Providing a debugging interception point for when a property changes at runtime - debugging when and where a property changed to a particular value can be quite difficult without this in some languages.
• Improved interoperability with libraries that are designed to operate against property getter/setters - Mocking, Serialization, and WPF come to mind.
• Allowing inheritors to change the semantics of how the property behaves and is exposed by overriding the getter/setter methods.
• Allowing the getter/setter to be passed around as lambda expressions rather than values.
• Getters and setters can allow different access levels - for example the get may be public, but the set could be protected.

For example, if foo was public, I could easily set it to null and then someone else could try to call a method on the object. But it's not there anymore! With a setFoo method, I could ensure that foo was never set to null.

Accessors and mutators also allow for encapsulation - if you aren't supposed to see the value once its set (perhaps it's set in the constructor and then used by methods, but never supposed to be changed), it will never been seen by anyone. But if you can allow other classes to see or change it, you can provide the proper accessor and/or mutator.

Download Stanford CoreNLP models using Maven

 <dependencies>  
 <dependency>  
   <groupId>edu.stanford.nlp</groupId>  
   <artifactId>stanford-corenlp</artifactId>  
   <version>3.2.0</version>  
 </dependency>  
 <dependency>  
   <groupId>edu.stanford.nlp</groupId>  
   <artifactId>stanford-corenlp</artifactId>  
   <version>3.2.0</version>  
   <classifier>models</classifier>  
 </dependency>  
 </dependencies>

How to generate UML Diagrams from Java code in Eclipse

UML diagrams compliment inline documentation ( javadoc ) and allow to better explore / understand a design. Moreover, you can print and bring them to table to discuss a design.

In this post, we will install and use the ObjectAid plugin for Eclipse to produce jUnit lib class diagrams. Then, we will be able to generate UML diagrams by simply dragging and dropping classes into the editor. We can further manipulate the diagram by selecting which references, operations or attributes to display.

Open Eclipse and go to Help > Install New Software
Click on add to add a new repository
Enter name ObjectAid UML Explorer
Enter Location http://www.objectaid.net/update