Java 7 and Groovy on Mac OS X Mountain Lion

I usually keep all my softwares and SDKs to the latest version but jdk7 was probably amongst the longest resisted update/upgrade. Mostly running groovy, I never got motivated enough to upgrade and then there have been several security and compatibility issues reported by many.

Anyways, today I just thought of doing it, primarily to reap benefits of invokedynamic, the thing I have not even looked at so far. The download was pretty simple in form of a .dmg and then the .pkg installer.

I fired up terminal with to check java and viola:

[~]
kunal@kaydee $ java -version
java version "1.7.0_11"
Java(TM) SE Runtime Environment (build 1.7.0_11-b21)
Java HotSpot(TM) 64-Bit Server VM (build 23.6-b04, mixed mode)

The second natural thing was to just verify groovy, but what the heck, the JVM version I see is:

[~] 
kunal@kaydee $ groovy -version
Groovy Version: 2.0.6 JVM: 1.6.0_37 Vendor: Apple Inc. OS: Mac OS X

Apparently Java 7 got installed at

/Library/Java/JavaVirtualMachines/jdk1.7.0_11.jdk/Contents/Home/

But the one available to groovy was something else:

[~]
kunal@kaydee $ groovysh
Groovy Shell (2.0.6, JVM: 1.6.0_37)
...
groovy:000> System.properties["java.home"]
===> /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home

Setting JAVA_HOME Environment variable comes to rescue (in .zshrc or .bash_profile or whatever profile file you use.)

export JAVA_HOME="/Library/Java/JavaVirtualMachines/jdk1.7.0_11.jdk/Contents/Home"

Reload the iTerm and

[~]
kunal@kaydee $ groovy -version
Groovy Version: 2.0.6 JVM: 1.7.0_11 Vendor: Oracle Corporation OS: Mac OS X

Presentation on Log4j

I had presented this some time back at my workplace. May be you'll find it useful.

Log4j Logging Mechanism

View SlideShare presentation or Upload your own. (tags: log4jjava)

Interesting Identifiers in Java

Ever seen a declaration like

_ _ = new _();

or call to a method like

System.out.println(_._());


Try this example, you'll see, these are valid java statements.
read on..

package test.identifiers;

/**
 * example that shows various legal identifiers
 * 
 * @author Kunal
 *
 */
public class LegalIdentifiers {

 int $1 = 1; // valid
 long _6 = 6L; // valid
 char t = '\t'; // of course valid, did u have any doubt ;)
 
 class t{
 } 
 t $;  // now here t is type & $ is object of type t

 class _{
  int _ = 0;
  int _(){ // method with name of constructor
   return _;
  }
 } 
 _ _ = new _(); // _ is an object of type _ (underscore)

 void display(){
  System.out.println(_._()); // interesting, isn't it?
 }
 // this is not a fill-in-the-blanks question
 // it actually compiles and runs :)

 // this means
 String String = "String";  // is valid
 // yes it is !!!
 // so you can have variable name same as class name
 
 public static void main(String[] args) {
  (new LegalIdentifiers()).display();
 }
}