Noulakaz

The blog of Avinash, Christina, Anya and Kyan Meetoo.

Technology

Beware of type erasure in Java

By 13 Comments

This Java program I got from a blog does not compile:

import java.util.*;

class Egg
{
}

class Muffin
{
}

public class Breakfast
{
  private List<Egg> eggs;
  private List<Muffin> muffins;

  public void add(List<Egg> moreEggs) {
    this.eggs.addAll(moreEggs);
  }

  public void add(List<Muffin> moreMuffins) {
    this.muffins.addAll(moreMuffins);
  }
}

The error message is:

name clash: add(java.util.List<Muffin>) and add(java.util.List<Egg>) have the same erasure

I was amazed when I saw that. I finally found an explanation in this forum.

What is happening is that (I quote) “Parameterized types (aka Generics) are only to restrict the use to enter the right object into the collection. All the generic information is erased by the compiler.”

So that why I got a name clash error. Both add(java.util.List<Muffin>) and add(java.util.List<Egg>) are in fact the same method add(java.util.List)!!!

Generics in Java are only used at compile time. They don’t even exist at run time!

PS:

I am a fan of Erasure, the group. Vince Clark was the initiator of Depeche Mode after all…

How I became a programmer

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It all started around 1986 (when I was 13) when my dad bought me a Sanyo MBC-16 PC. It had an Intel 8088 processor running at 8MHz (compared to the 2000MHz Intel Core Duo I am using now), 640kb of RAM (I now have 2,000,000kb) and ran MS-DOS 3.22.

One nice “feature” of that PC was that it came with two floppies only (it didn’t have a hard disk). The first floppy contained the operating system and the second one was GW-BASIC.

GW-BASIC (do you know what GW means?) was without doubt the reason I became a Computer Scientist (so, thanks Bill!). Remember, I bought that PC when I was 13 and the only way for me to play was to write my own games. So this is what I did. I wrote numerous Space Invaders clones and I wrote my own version of Tron with a very slow collision detection algorithm…

I had one friend at Royal College Curepipe who was also a computer maniac. I think his name was Harry and he died when we were still in college… Anyway, one day he gave me one floppy containing one executable: turbo.com

I went home and ran it. It was Turbo Pascal 1.0 and I couldn’t program anything as I didn’t know the Pascal language. I did what all good geek would do: I looked inside the executable and I found a data segment containing all the Pascal keywords (program, var, type, writeln, etc.).

I guess I tried all kinds of combinations for days until I became a fairly good Pascal programmer. I then wrote my own Mastermind game. I also fondly remember typing a maze-generating and -solving program I got from SVM magazine. Those were the great pre-Internet and pre-Google days where you really had to be motivated to learn something new…

This PC had two graphical modes: one was 320×200 with 4 colors out of 16 and the other one was 640×200 monochrome. This was the CGA standard.

As the color palette was so limited (4 out of 16 colors compared to the 16,777,216 we have today), games tended to look the same :-)

I fondly remember King’s Quest I by Sierra and Karateka by Jordan Mechner:

My next computer was a Commodore Amiga 500 but I’ll write about it in a future post…

Declining interest in Computer Science

By 39 Comments

As written here:

An analysis of survey results from the Higher Education Research Institute at the University of California at Los Angeles (HERI/UCLA) indicates that the popularity of computer science (CS) as a major among incoming [first year students] at all undergraduate institutions has dropped significantly in the past four years.

The survey was made in 2005 and the Higher Education Research Institute people only looked at US universities. Nevertheless, I think that this trend is general and is relatively easy to understand.

The first peak, which happened around 1983, was when the microcomputer became pervasive. Suddenly, computers were affordable and many people could finally afford to buy one. This was the era of the Sinclair ZX Spectrum and the Commodore 64. Geeks could finally opt to join a department full of other geeks :-)

The decline from 1986 to 1996 was when people realized that having (or even liking) a computer at home to play games does not make you a Computer Scientist. Being a Computer Scientist implies thinking like a Computer Scientist and not merely liking computers…

The second peak, which happened around 2000, was when Internet came together with its bubble. Lots of youngsters chose CS as they wanted to create the new IBMs and Microsofts. They wanted to emulate Google and Yahoo! and they thought this was easy.

The decline from 2000 onwards was when people found out that emulating Google and Yahoo! was not easy. Sure, they loved to browse the web but they could not build a successful company. And the whole Western economy nearly crashed!

The situation in Mauritius

According to my observations, we had a peak a few years ago when people started talking about the Cyberisland concept. Lots of youngsters chose CS because they dreamed of working in the Cybertower to get a lot of money. This is when lots of centers offering “computer” courses appeared out of nowhere…

Since then, I have notice a decline. Many youngsters have realized that one needs the correct aptitudes to succeed in CS. If someone does not have those aptitudes, then it’s much better for that person to choose something else where he/she has a much higher probability of succeeding. They have also found out that things are not that rosy in the Cybertower…

This is a good thing in my opinion.

Mauritius is a small country with few resources. It’s so much better to let people chose their career based on their aptitudes. Some will become great Computer Scientists. And some will become great singers. That’s how it works everywhere else.

Ask Michael Jackson and Michael Jackson.