Re: Deprecation in the JDK

August 7th, 2009 jlee 1 comment

Everyone hates the deprecation policies of the JDK team but it’s certainly an understandable policy.  Millions and millions of lines of code exist out in the wild and there’s no telling what calamity would befall us if methods were actually removed the JRE libs.  On the other hand, people still use those deprecated methods despite their failings and the presence of better options.  I was reading Joseph Darcy’s blog entry on this policy and ran across an interesting comment.

The idea is pretty simple:  make compiling fail against the deprecated methods without actually removing them from code.  This preserves binary compatibility while preventing any new code from compiling against these methods.  This would actually include new releases of applications written before the method was deprecated as these new versions would no longer compile while the previous releases would still run.

This seems to be the best of both worlds.  Building on the idea from comment, I’d offer this enhancement:  Introduce an @Obsolete annotation.  This would supplant the @Deprecated annotation on these methods.  Any usage of a method or class (or field?) with this annotation would return an error at compile time.  Reflective access to these items would also be disallowed just to drive the point home.  Of course, the annotations would need to include facilities to describe the alternatives to use for these old methods to provide the same functionality as the javadoc comment.  Given this simple addition, I think we’d finally start to make some progress on modernizing our code.

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Categories: Java

Your project needs someone like me

June 29th, 2009 jlee 3 comments

I have a mild compulsion to clean up code.  When i see mixed indentation (usually tabs vs spaces), I start getting twitchy.  When I see star imports, places where old loops can be replace with the “new” foreach loops (thereby reducing line noise in many cases), or any of a number of different “improvements” to the code I start itching to start cleaning up.  But there’s (at least) one problem:  not everyone wants their code cleaned up.

For many, such janitorial efforts hide any actual functionality changes and they would prefer such changes be made in a separate commit/task.  While there’s some merit to that complaint, it’s also often true that time for mere janitorial work will rarely/never get allocated.  So without taking advantage of opportunities, it will never get done.  Unless you work on a project that values such changes, these changes will either be made alongside functional fixes or not at all.

To resolve this tension, there are things both camps can do.  If your project is open source, you could implement something like The Linux Kernel Janitor Project.  This project is used as one possible entry point for beginners to begin to learn the system and make some changes without necessarily having to know enough to effect major changes.  This kind of project can work in a corporate setting as well, though most companies would prefer to get some “value” from their employees as quickly as possible.

If a janitorial project is not an option, then try to grant some leeway for intermittent clean up.  If code isn’t maintained, it can become so crufty over time that making actual bug fixes or functional enhancements can be difficult.  On the flip side, those like me that like to get code into shape need to show some restraint and courtesy.

Sometimes its just pride that rebels against having someone else muck with “my” code that leads people to object to such changes.  But in many cases, drastic and pervasive reformats or “tweaks” to code can lead to impossible to decipher merge conflicts for people doing significant changes in those files.  It can be tempting (and gratifying) to do a deep clean on a file or whole sets of files but you have to consider the impact of those changes.  You might have to settle for one or two things to clean up this time and catch the rest later.  At the end of the day, it’s about making a working product and if your cleanups cause delays for others as they sort out what exactly you did, then you’re not exactly helping out.

Of course, prevention is the best medicine so each project should choose a set of standards and conventions.  These could include a set of libraries that everyone agrees to use.  This can lead to a set of standard/best practices in the project rather than everyone choosing their own favorite XML libary for their subsystem, e.g.  It should certainly include code style conventions.  For me, I choose the Sun conventions. There’s nothing magical about them.  I like them and encourage their use.  But whatever works for your team, just pick something and stick to it.  This will help reduce the need in the future for large scale janitorial work.

The criteria for what is the “right” way to do things can change over time.  e.g., the foreach loop is newer than most java code, I’d wager.  On older code you’re still likely to see many while loops or old style for loops that could be migrated to the new style.  Your team’s style/practice guidelines should be periodically reviewed and update to account for the change landscape in both language features and third party libraries.  Once any changes are agreed upon, you need to prepare yourself for those changes to start trickling in.  These can be done in an organized sweep and clean up of the code or piecemeal by individuals as they find them.

Either way, you’re going to want people like me in there to help.

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Categories: Java

Some Post JavaOne Fun

June 6th, 2009 jlee Comments off

It’s friday night.  Finally back at the hotel without a meeting or party or a session to go to.  What else is there to do but port benchmarks of debatable value to my favorite new non-Java language:  Fan.  Earlier in the I was directed to this blog post detailing some performance problems with groovy.  Yes, I know the blog is old.  That’s not the point I want to make here.  This week at Javaone, there was a presentation doing some more performance comparisons between languages on the JVM.  This one caught my eye because it’s the first one I’ve seen in the wild that included Fan.  So this got me thinking about year old post and the ray tracing exercise.  How would fan hold up?  I decided to find out.  Because there’s no better way to spend a Friday night after long conference week, right?

The Fan code isn’t idiomatic (I’m not that bored tonight).  It’s just a quick and dirty port from the Java source to Fan.  For reference, I reran the Java version and then the Fan version.  This test is running on OS X and Java 1.6u13.  Without further hand waving, here’s the results:

time java -cp . ray 8 512
 
real	0m14.210s
user	0m12.443s
sys	0m1.313s
 
time fan tracer::RayTest 8 512 
 
real	0m17.700s
user	0m15.832s
sys	0m0.672s

As you can see, the performance is really quite good. I’ll probably play with the source over the next few days and see if I can’t improve it a bit. The fan code is pretty rough so there’s probably a fair bit to be done to speed that up a bit.  I’ll attach the source so if anyone else is interested the source will be available.  I have to say, though, that’s not too shabby at all.

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Categories: Java, fan

The Kindle is Here!

March 4th, 2009 jlee Comments off

I finally broke down and bought a Kindle.  I’ve been eyeballing them since the first one came out and have been daydreaming about them since the Kindle 2 pics first leaked.  After reading countless previews and reviews and raves and rants, I decided it was time.  Sure, it’s expensive.  Yeah, it’s “only a single function device.”  blahblahblah.  The fact is I love to read, I live in a NYC apartment, and I already have an entire wall devoted to bookshelves crammed full of my books.  There’s just not that much space here to keep buying more and more books.  Any my library hardly ever has what I want on the shelf.  When they have it at all, there’s a waiting list.  So this makes a lot of sense for me in a number of ways.  I’ve had it for about an hour now so I don’t have any deep dive experience with it as such, but as far as first impressions go, it’s a big win.  And the first thing I did after browsing through the user’s guide?  I bought Brandon Sanderson’s latest book “The Hero of the Ages.” Now if only I didn’t have to work.

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Categories: General, kindle

String Concatenation Revisited

February 23rd, 2009 jlee 4 comments
This entry is part 5 of 5 in the series Tips

I had intended to do some follow up numbers to my previous post but I got a bit sidetracked by work and the like.  My simple tests all work with one String that’s created then thrown away.  This test helped me resolve the question I had when I started down that road but stops short of a more general answer.  Then I saw this pingback which led me here.  There’s some nice analysis and insights to consider.  So given the shortcomings of my little benchmark and the comments there, I wanted to expand my test a bit and see what things look like when the loop doesn’t throw away the data.  The test is simple enough again:

import java.util.*;
import java.text.*;
 
public class ConcatenationTest {
	private static long concat(int count) {
		long start = System.currentTimeMillis();
		for(int x = 0; x < count; x++) {
			String s = "Loop " + x + " of " + count + " iterations.";
		}
		return System.currentTimeMillis() - start;
	}
 
	private static long append(int count) {
		long start = System.currentTimeMillis();
		for(int x = 0; x < count; x++) {
			String s = new StringBuilder("Loop ")
				.append(x)
				.append(" of ")
				.append(count)
				.append("iterations.")
				.toString();
		}
		return System.currentTimeMillis() - start;
	}
 
	private static long concatAcrossLoops(int count) {
		long start = System.currentTimeMillis();
		String s = "";
		for(int x = 0; x < count; x++) {
			s += "Loop " + x + " of " + count + " iterations.";
		}
		long time = System.currentTimeMillis() - start;
		System.out.println("concatAcrossLoops time = " + time);
		return time;
	}
 
	private static long appendAcrossLoops(int count) {
		long start = System.currentTimeMillis();
		StringBuilder s = new StringBuilder();
		for(int x = 0; x < count; x++) {
			s.append("\nLoop ")
				.append(x)
				.append(" of ")
				.append(count)
				.append("iterations.");
		}
		long time = System.currentTimeMillis() - start;
		System.out.println("appendAcrossLoops time = " + time);
		return time;
	}
 
	public static void main(String[] args) {
		int count = 10000;
		List concats = new ArrayList();
		List appends = new ArrayList();
		List concatsAcross = new ArrayList();
		List appendsAcross = new ArrayList();
		for(int x = 0; x < 10; x++) {
			concats.add(concat(count));
			appends.add(append(count));
			concatsAcross.add(concatAcrossLoops(count));
			appendsAcross.add(appendAcrossLoops(count));
		}
 
		String header = "concats   appends   concats across loops   appends across loops";
		String format = "%7d %9d %22d %22d\n";
		System.out.println(header);
		for(int x = 0; x < 10; x++) {
			System.out.printf(format, concats.get(x), appends.get(x), concatsAcross.get(x), appendsAcross.get(x));
		}
	}
}

And then the results:

concats appends concats across loops appends across loops
48 14 18990 1276
27 11 14581 1442
4 4 13206 1253
3 3 13478 1438
4 4 12651 1444
4 3 12485 1403
4 3 12608 1318
4 3 13152 1312
3 4 12535 1390
4 3 12444 1329

Notice after the first two loops the numbers for all runs drops. As the JIT compiler kicks in, we get some optimization but as you can see concatenation across loop iterations is incredibly much more expensive. In this case, StringBuilder is still the clear winner.

update
There was a typo in the original test. I was calling toString() in the appendsAcrossLoop test which was entirely unnecessary. (I forgot to remove that call when adapting from the earlier iteration.) The new results are below. I included them here rather than just replacing the table above as it shows just how expensive that toString() is.

concats appends concats across loops appends across loops
42 15 16562 4
5 8 12564 5
4 3 11601 2
4 2 11141 2
4 3 11025 3
3 3 11260 3
3 3 11062 3
3 3 11738 2
4 2 11078 2
4 2 11130 3
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Categories: Java