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Minfo.SeLab2r1.4 - 17 Oct 2012 - 16:28 - KrikavaFiliptopic end
---+ Lab 2 : Reflection

%TOC%

---++ Introduction

In this lab we will overview some of the basic principle of [[http://en.wikipedia.org/wiki/Reflection_(computer_programming)][reflection]] [[http://docs.oracle.com/javase/tutorial/reflect/index.html][in Java]].

Create a new project in Eclipse ==tp2== for today's exercises.

---++ Exercise 1 : A class analyzer

Start by copying the following [[https://gist.github.com/3902457][source]] into your new Eclipse project.

---+++ Exercise 1.1 : No generics version

Write a simple class analyzer. Such an analyzer expects a name of a class and it will print to the standard output its interface: its declaration, declared fields, constructors and methods.

Here is a sample output given ==java.util.ArrayList== as an input:

<!-- <pre> -->
<script src="https://gist.github.com/3902390.js?file=gistfile1.java">
</script>
<!-- </pre> -->

For start do not worry about generics. There is a bonus exercise for you to do if you have enough time (meaning you have completed all the other exercises) or to do at home.

   * Do not use ==toString()== neither ==toGenericString()== method
   * Try to work iteratively and test as you go
   * Try to refactor as you go (hint: think about a ==mkString== method that will combine an array to a String with a separator)
   * The interactive behavior of the program is not very handy for testing. Think how can you speed up the development cycle (code/test).

---+++ Exercise 1.2 : Non interactive version

Modify the program so it can run non interactively taking its input from command line. For example I should be able to run it like:

<verbatim>
$ java tp2.ClassAnalyzer java.util.Data java.util.ArrayList
</verbatim>

---+++ Extra Exercise 1.3 : Generics version

Try to include the generics type information.

---+++ Extra Exercise 1.4 : Generics version with annotations

Try to include runtime annotations.

   * Think about all the places an annotation can occur
   * Print also arguments of the annotations' parameters

---+++ Extra Exercise 1.5: Global list of imports

Use only simple class names and include a list of imports right after package declaration. Think about to handle duplicates (==java.util.List==, ==java.awt.List==). When you look at how Eclipse organizes the imports, it groups together same package imports, you could try to do the same.

---++ Exercise 2 : A generic ==toString()== method

In the creature simulator's ==AbstractCreature== class from the previous lab write a generic ==toString()== method:

<verbatim>
public String toString() {...}
</verbatim>

which will output all of the creature's attributes (fields). It has to be generic method since subclasses of the ==AbstractCreature== can define their own attributes this class is not aware of.

   * Think what is the difference between ==getDeclaredFields()== and ==getFields()==
   * To test it, you can add some more attributes to the ==SmartCreature==

---++ Exercise 3 : Array Grow

   * Get [[https://gist.github.com/3902612][ArrayGrowTest.java]], taken from the [[http://www.horstmann.com/corejava.html][Core Java]] book. 
   * Complete the method ==goodArrayGrow()== 

Once you complete the method and run, you should see following output:

<verbatim>
[1, 2, 3, 0, 0, 0]
[Maurice Chombier, Francois Pignon, null, null]
The following call will generate an exception.
Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ltp2.ArrayGrowTest2$Personne;
...
</verbatim>

The nulls on the first line are fine - proving the the array has grown

   * Look at the methods from the ==java.util.Arrays== class.
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