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Tuesday, December 13, 2005

Converting Arrays to Lists in Java 5

I'm trying to write some Java 5 (or 1.5, whatever) code for the first time. This is how I used to convert an array to a List in 1.4:
List list = Arrays.asList(intArray);
However, Java 5 gives me an error as Arrays.asList(intArray) actually returns a List<int[]>. That's right, a list of int arrays with a size of 1 instead of a List<Integer>, List of ints with size intArray.length.

So is this correct? Does Arrays.asList(intArray) no longer work for my needs?

For now I am forced to use the following, unless someone can show me the light:

List<Integer> list = new ArrayList<Integer>();
for (Integer i : intArray) list.add(i);


Update:
j yu has helped me to understand the issue at hand, as I have noted in the comments below. Here is the logic for easier viewing...

Under 1.4, you will receive a compile time error for asList(int[]), but under 1.5 asList(int[]) is acceptable with the varargs implementation. 1.5 accepts the array as an object and creates a List<int[]> instead of the List<Integer> that I had expected through autoboxing.

Try this for yourself:
int[] intArray = new int[] { 1, 2, 3, 4, 5, 6 };
System.out.println(Arrays.asList(intArray).size());

Integer[] integerArray = new Integer[] { 1, 2, 3, 4, 5, 6 };
System.out.println(Arrays.asList(integerArray).size());


Your output will be:
1
6

Since the asList works very differently with int[] and Integer[].

Maybe this should be a warning in Eclipse? It is confusing for both expert and novice users. Or should this even be the correct approach? Shouldn't the Arrays.asList(int[]) autobox the int's into a Integer[] for you?

Or is there still an easier solution for me? Maybe through casting or generics? I stumbled upon this while converting int[] to List during a Topcoder event, after updating my jdk from 1.4 to 1.5


Update #2:
In a normal app, it would be easy for me to import the Apache Lang jar, and use ArrayUtils.toObject(intArray). However I'm trying to do this inside of the Topcoder arena applet, so I can't include any external jars. That's why I was looking for an api level solution.

Friday, December 09, 2005

Trying new Code Review Tool

I've been wanting to better organize a structured code review on our project. So today I'm looking at the CSDL Jupiter Code Review Tool.

It looks promising, in that no external DB is required. It stores all review info in xml documents that are shared through our normal CVS project. It's an Eclipse plugin, which will make it easy to install and get our developers up to speed.

And they have a nice user's guide.

I'm hoping it fulfills our needs, and I'll post the results of my review after a day or so of use. It should be a big improvement over the print / distribute / highlight review!

Thursday, December 01, 2005

Eclipse.org redesign... Very Nice!

After complaining in the past about the Eclipse website, I'm really impressed with their site redesign. I especially like how easy it is to download the Eclipse SDK now from their new downloads area! Finally, a person unfamiliar with the umbrella Eclipse organization can simply download the Eclipse SDK IDE without stumbling through the maze of projects.

Nicely done! It's much more elegant and far lower on the confusing scale.