Wednesday Java Quiz: Think You Understand Concurrency?
There is a war of words going on about simplicity vs. complexity among the pundit circles:
- Joel Spolsky: The Duct Tape Programmer
- Robert Martin: The Duct Tape Programmer, Echoes from the Stone Age
- Tim Bray: On Duct Tape
- Peter Seibel: Unit testing in Coders at Work
- CodeToJoy: The Emperor's New Prose: Duct Tape Blogging
They argue about many things, including test-driven development, architectures, design patterns and threading:
Joel Spolsky: One principle duct tape programmers understand well is that any kind of coding technique that’s even slightly complicated is going to doom your project. Duct tape programmers tend to avoid C++, templates, multiple inheritance, multithreading, COM, CORBA, and a host of other technologies that are all totally reasonable, when you think long and hard about them, but are, honestly, just a little bit too hard for the human brain.
Robert Martin: I found myself annoyed at Joel’s notion that most programmers aren’t smart enough to use templates, design patterns, multi-threading, COM, etc. I don’t think that’s the case. I think that any programmer that’s not smart enough to use tools like that is probably not smart enough to be a programmer period.
While I had my "A-Ha, so this is how TDD works!" moment at a Robert Martin "Scoring Bowling Game" talk, I don't want to argue against Joel either.
Since I'm fixing some long standing bugs (Chris told me "It's been there for years" yesterday) in a piece of software recently, and it has a threading aspect to it, I'll just throw out snippets that I saw while walking through the code, all I ask is:
Q: What's wrong with them? (They are not complete. Use your imagination to fill in the missing parts.)
Snippet 1
public void foo() {
Object lock = task.getLock();
synchronized(lock) {
task.perform();
lock.wait();
}
}
Snippet 2
public void run() {
while (!done) {
doIt();
if (done) break;
try {
Thread.sleep(60000L);
} catch (InterruptedException e) {
}
}
}
public void stop() {
done = true;
while (thread.isAlive()) {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
}
}
}
Snippet 3
public void foo() {
// code
class Bar {}
Object lock = new Bar();
synchronized(lock) {
// code
lock.wait();
}
// code
synchronized(lock) {
// code
lock.notify();
}
}