Which Programming Language J. Gosling Would Use Now, Except Java?
>>> Updated later
Maybe we can get completeness of J. Gosling's opinions about Java/Scaka/JVM from here
===
According to Adam Bien's blog from JavaOne
During a meeting in the Community Corner (java.net booth) with James Gosling, a participant asked an interesting question: "Which Programming Language would you use *now* on top of JVM, except Java?". The answer was surprisingly fast and very clear: - Scala.
I think Fortress will also be a very good future choice when it gets mature.
Posted at 07:39AM May 08, 2008 by dcaoyuan in Java |
Some Tips for Upgrading to Rails 1.2.x
Bellow are some issues that I met when upgraded from rails 1.1.6 to 1.2.x:
1.About enrivonment.rb
Make sure your application configuration behind:
Rails::Initializer.run do |config| ... end
I met this issue when I put following code:
require 'environments/localization_environment' require 'localization' Localization::load_localized_strings require 'environments/user_environment'
before that closure, which works under 1.1.6, but don't under 1.2.x
2.About ActionMailer::Base.server_settings
If you get errors like:
uninitialized constant ActiveSupport::Deprecation::RAILS_DEFAULT_LOGGER (NameError)
try to change your ActionMailer::Base.server_settings to ActionMailer::Base.smtp_settings
3.Put all "include" statements inside class definitions
You must put include statements inside class/module definitions instead of outside a class/module definition in Rails 1.2.x. Otherwise, you'll get:
Error calling Dispatcher.dispatch #<NameError: cannot remove Object::COPYRIGHT>
Posted at 11:35AM Mar 07, 2007 by dcaoyuan in Java | Comments[1]
Functinal Style Ruby
After playing with Ruby for weeks, I found Ruby is yet interesting. I try to write my code a bit in the likeness of Erlang, where symbol vs atom, array vs list. And the most important syntax that I like are:
- everything return a value
- may return multiple values
- begin-end clause is lambda that may be directly applied
- parallel assignment
Now, let's write some code before and after (functional):
Example1:
Before
1. cond = {}
2. if par[:id]
3. feed = Feed.find(par[:id])
4. if feed
5. cond[:feed] = feed.id
6. end
7. end
8. if par[:m]
9. limit = par[:m].to_i
10. else
11. limit = 20
12. end
13. if limit >= 4096
14. limit = 4096
15. end
16. cond[:limit] = limit
17. if par[:d]
18. days = par[:d].to_f
19. if days <= 0 || days >= 365
20. days = 365
21. end
22. cond[:time] = Time.now - days*86400
23. end
After
1. cond = {
2. :feed => if par[:id]
3. feed = Feed.find(par[:id])
4. feed ? feed.id : nil
5. end,
6. :limit => begin
7. limit = par[:m] ? par[:m].to_i : 20
8. limit >= 4096 ? 4096 : limit
9. end,
10. :time => if par[:d]
11. days = par[:d].to_f
12. days = days <= 0 || days >= 365 ? 365 : days
13. Time.now - days * 86400
14. end,
15. }.delete_if { |k, v| v.nil? } # delete all nil elements of cond
Example2:
Before
1. if f[:mode] == "rss" 2. rss = f[:feed] 3. params[:feed][:channel] = rss.channel.title 4. params[:feed][:description] = rss.channel.description 5. params[:feed][:link] = rss.channel.link 6. params[:feed][:copyright] = rss.channel.copyright 7. else 8. atom = f[:feed] 9. params[:feed][:channel] = atom.title 10. params[:feed][:description] = atom.subtitle 11. params[:feed][:link] = atom.links.join 12. params[:feed][:copyright] = atom.rights 13. endAfter
1. params[:feed][:channel], 2. params[:feed][:description], 3. params[:feed][:link], 4. params[:feed][:copyright] = if f[:mode] == "rss" 5. rss = f[:feed] 6. 7. [rss.channel.title, 8. rss.channel.description, 9. rss.channel.link, 10. rss.channel.copyright] 11. else 12. atom = f[:feed] 13. 14. [atom.title, 15. atom.subtitle, 16. atom.links.join, 17. atom.rights] 18. end
Example3
1. # grp_str: p -> public(0) , u -> user(1), f -> friends(2)
2. def privilege_cond(user, grp_str)
3. grp_str ||= 'puf'
4. cond = {:pre => "", :sub => []}
5. cond = if loggedin?(user)
6. frds = grp_str.include?('f') ? user.friends.find(:all) : []
7. frd_ids = frds.collect { |frd| frd.friend_id.to_i }
8.
9. cond = if grp_str.include?('u')
10. {:pre => cond[:pre] + (cond[:pre] == "" ? "" : "OR") +
11. " user_id = ? ",
12. :sub => cond[:sub] + [user.id]}
13. else
14. cond
15. end
16.
17. cond = if grp_str.include?('f') && !frd_ids.empty?
18. {:pre => cond[:pre] + (cond[:pre] == "" ? "" : "OR") +
19. " user_id in (?) AND privilege in (?) ",
20. :sub => cond[:sub] + [frd_ids, [0, 2]]}
21. else
22. cond
23. end
24.
25. cond = if grp_str.include?('p')
26. {:pre => cond[:pre] + (cond[:pre] == "" ? "" : "OR") +
27. " user_id != ? AND privilege = ? ",
28. :sub => cond[:sub] + [user.id, 0]}
29. else
30. cond
31. end
32. else
33. {:pre => "privilege = ?",
34. :sub => [0]}
35. end
36. end
Posted at 11:10AM Feb 07, 2007 by dcaoyuan in Java |
Java + Ruby + Erlang = JRE (Just Running Environment)
I'm recently doing a project under Ruby on Rail. It seems to be a reasonable programmer today, one should take at least > 3 languages.
Personally,
I like Erlang: lightweight process + message passing + functional programming + dynamic. It exactly matches my philosophy of looking the real world, and I think it's what functional programming should be.
Are there really Objects exist? I'm not sure. Instead, talking about OO, Object Oriented may be more sense. That is, an Object makes sense only when you orient it. All states look like being "in" an object, are with meaning only when you measure them. But, doesn't "measure" mean applying a "Function" on it? So, the states should always be carried only by functions rather than 'object', and the states are time streaming, they will be transfered from one function to another function, another function ..., so you catch the meaning of them when you track the functions chain, the meaning is based on the functions rather than the name of a Class as a member of. When you want to take a snapshot on them, you save them some where, such as showing on screen, stored in database, printed on paper what ever.
I like Java: tons of APIs + open source code base + Swing + NetBeans. So far, it has the best cross-platform UI tool kit to my eye. I like Swing, I can change or extend it easily to whatever I want. But things go easy because so many people have taken extremely efforts on it. It's bound too Objected, people split world to objects, then try to composite them or inherit something called super to make them together again. I feel pain when doing this, I have to split them, composite them in a way, then things change (or, the real world is still there), I split them, composite them in another way, again and again, it's called re-factor, but people may never catch the real Factor of the real world.
I, have to learn Ruby. Ruby and Rails are very good. For developers term, you should always know things are not so philosophy as yours, you will have guys thinking in different ways, of the real world. So Ruby is there, everyone can think the real world according to his understanding, yeah, in different ways, and, to make them not going too far away, you need rails.
So, I have to learn Java, as a tool make me doing many things interesting and painful; I have to learn Ruby, as a tool make my guys doing many things interesting and on rails; And I'll keep Erlang (Lisp/Scheme) as a tool make me not only doing but also thinking with interesting.
Posted at 09:24AM Jan 29, 2007 by dcaoyuan in Java |
No Static Method in Interface, So I Write Code As ...
Java does not support static method in interface. But sometimes, I just want a static method to say: PersistenceManager.getDefault(), where PersistenceManager is going to be an interface. I don't like to add one more class named PersistenceManagerFactory, with a method:
public static PersistenceManager PersistenceManagerFactory.getDefault()
So I write code like:
public class PersistenceManager {
private static I i;
public static I getDefault() {
return i == null ? i = ServiceLoader.load(I.class).iterator().next() : i;
}
/** The interface I, which is actually the PersistenceManager should be: */
public static interface I {
void saveQuotes(String symbol, Frequency freq, List quotes);
List restoreQuotes(String symbol, Frequency freq);
void deleteQuotes(String symbol, Frequency freq, long fromTime);
void dropAllQuoteTables(String symbol);
void shutdown();
QuotePool getQuotePool();
TickerPool getTickerPool();
}
}
Then implement the PersistenceManager.I in another package, like:
public class NetBeansPersistenceManager implements PersistenceManager.I {
...
}
And declare it under the META-INF as:
core/src/META-INF/services/org.aiotrade.math.PersistenceManager$I
which contains one line:
org.aiotrade.platform.core.netbeans.NetBeansPersistenceManager
I can call PersistenceManager.getDefault().showdown() now.
Posted at 08:01AM Dec 08, 2006 by dcaoyuan in Java | Comments[4]
A Regress Bug in java.awt.geom.Path2D (JDK 6.0 beta 2)
I tested AIOTrade on newly downloaded JDK 6.0 beta 2, and got an exception instantly:
java.lang.ArrayIndexOutOfBoundsException: 0
at java.awt.geom.Path2D$Float.moveTo(Path2D.java:322)
at java.awt.geom.Path2D$Float.append(Path2D.java:643)
at java.awt.geom.Path2D.append(Path2D.java:1780)
The code run good in JDK 5.0, so will it be a regress bug in JDK 6.0?
I then checked the source code: 6.0 vs 5.0, and found there were likely a bit of code omited wrongly. That is, in method body of void needRoom(boolean needMove, int newCoords), should add
if (grow < 1) {
grow = 1;
}
at the next of:
int size = pointTypes.length;
if (numTypes >= size) {
int grow = size;
if (grow > EXPAND_MAX) {
grow = EXPAND_MAX;
}
The following is the proper code I've tested OK:
void needRoom(boolean needMove, int newCoords) {
if (needMove && numTypes == 0) {
throw new IllegalPathStateException("missing initial moveto "+
"in path definition");
}
int size = pointTypes.length;
if (numTypes >= size) {
int grow = size;
if (grow > EXPAND_MAX) {
grow = EXPAND_MAX;
}
/** fix bug:
* java.lang.ArrayIndexOutOfBoundsException: 0
* at java.awt.geom.Path2D$Float.moveTo(Path2D.java:322)
* at java.awt.geom.Path2D$Float.append(Path2D.java:643)
* at java.awt.geom.Path2D.append(Path2D.java:1780)
*/
if (grow < 1) {
grow = 1;
}
pointTypes = Arrays.copyOf(pointTypes, size+grow);
}
size = floatCoords.length;
if (numCoords + newCoords > size) {
int grow = size;
if (grow > EXPAND_MAX * 2) {
grow = EXPAND_MAX * 2;
}
if (grow < newCoords) {
grow = newCoords;
}
floatCoords = Arrays.copyOf(floatCoords, size+grow);
}
}
As I can not wait for it be fixed in JDK, so I wrote another org.aiotrade.util.awt.geom.Path2D and org.aiotrade.util.awt.geom.GeneralPath, and replaced the java.awt.geom.GeneralPath in my source tree. you can get the code at:
Posted at 11:38PM Sep 24, 2006 by dcaoyuan in Java |
Install XWiki on Glassfish and Derby
I've upgraded blogtrade.org to glassfish b48, with XWiki and javadb (Apache Derby) integrated. Here is a short guide I posted:
http://blogtrader.org/wiki/bin/view/KnowledgeBase/XWikiGlassfishDerby
Posted at 04:51AM May 23, 2006 by dcaoyuan in Java |
Based on Glassfish b42
The blogtrader.org and blogtrader.net are now based on the newest Glassfish Application Server b42. As Glassfish is also the default bundled J2EE server of NetBeans IDE, with a database: javadb, it's an ideal environment for the developing of BlogTrader Project. I hope to provide stock symbols updating service via a web site to BlogTrader Platform, thus I can add the information of each market, such as local time, open, close hours ect. and you'll need not to input symbol for each stock.
And, the modules updating centre could also be set.
Posted at 11:00AM Mar 30, 2006 by dcaoyuan in Java | Comments[23]