What I like in C# 3.0 and what I would like to see in Java

Nevertheless I'm working mostly with Java right now, Microsoft .NET platform and C# is also the stuff I'm very interested to know. I've been developing on Microsoft .NET since 2002 and I'm really excited how such efforts and investments Microsoft is putting to it. Sun seems to miss the train ...

Java 1.5 had been a great, innovative release either of the language and platform. Sun's answer to Microsoft's C# 2.0. But not enough ... Microsoft delivered C# 3.0 so far with great features inside: enhanced initialization (type instances & collections), anonymous types and delegates, LINQ, lambda-functions ( == closures) ... As a developer, I'm really excited about those things. Many of them I would like to have in Java as well.

1) Collection initialization

Collection < int > integers = new ArrayList< int >() { 1, 2, 3, 4 };
ArrayList < int > list = { 1, 2, 3, 4 };

2) Closures

This is a most wanted featured I guess. Any modern language has to support it. Groovy is very good complementary of Java with excellent language syntax tradeoffs.

db.eachRow( "SELECT * FROM uses" ) { user ->
// Do something here
}

3) Class initialization by property names

Employee employee = new Employee() {
FirstName = "Bob",
LastName = "Smith"
};

4) Enhanced generics (parametrized types) support
Even Java 1.5 brings something like C# generics (which both are similar to C++ templates), the Java's implementation is the worst. It's my point of view.

// I would like to have something like this. Of course, it means that some
// type T has to have default constructor. C# uses constraints for that
// (like new()) so why Java doesn't?
class A<> {
private T t = new T();
};

// Why it's impossible to get the class of generic type parameter?
// Sure, taking into account that it's impossible for int, double, ...
// there're reasons for that behavior. Again, why don't we use constraints
// for that (like class)?
class A {
<T>void func( T ) {
Class< ? > t = T.class;
}
};

5) Default type value

int t = default( int );
Integer t = default( Integer.class );

Hope, Sun is going to thieve something from C# in put it to the Java. Will see ...

Java and dynamic languages

Dynamic languages (like Ruby, Groovy) are quite popular in nowadays. As for me it's a big challenge for developers to learn and use at least one dynamic language in every day job. Of course, there should be a good reason to do that.

So today I would like to demonstrate some examples how I'm using Groovy to write tests for Java classes I've been developing. What's very interesting that it's possible to combine Java and Groovy code seamlessly within one project (== one jar) and everything works just fine.

Let's start with an example.

Assume, in our project we heavily use image processing class ImageUtils with static methods scaleHighQuality and scaleLowQuality, which perform image scaling. For testing purposes, we've included a bunch of images as resources to our jar. Let's develop test case witch goes through all image resources, scales each image (up or down) to 125x125 pixels with low- and high-quality scaling algorithms.

import org.junit.Test
import java.awt.image.BufferedImage
import javax.imageio.ImageIO

public class ImagesTestCase extends GroovyTestCase {
  private void scale( Closure c ) {
    URL location = new URL(
       getClass().getProtectionDomain().getCodeSource().getLocation(),
       ""
    )

    // Enumerate all image resources
    new File( location.toURI() ).list().each() { file ->
      if( file.toLowerCase() =~ /(png|gif|jpg)$/ ) {
        BufferedImage image = ImageIO.read( new URL( location, file ) )
        assertNotNull( "Input image is null", image )

        BufferedImage transformed = c( image );
        assertNotNull( "Transformed image is null", resized )

        assertTrue( transformed.getWidth() <= 125 )         
        assertTrue( transformed.getHeight() <= 125 )       
      }     
    }  
  }   

  @Test  public void testImagesLowQuality() {    
    scale() { image ->
      ImageUtils.scaleLowQuality( image, 125, 125 )
    }
  }

  @Test
  public void testImagesHighQuality() {
    scale() { image ->
      ImageUtils.scaleHighQuality( image, 125, 125 )
    }
  }
}

Why I'm using Groovy for that?
1) It's much faster to write a test code (simplified syntax)
2) Tests look more accurate and compact (powerful library)
3) Groovy has a bunch of modern features which make development even more pleasant (closures, regular expressions, ...)

I would say, "Developers, keep in touch with dynamic languages!"