Gopi Balaji

Jim,

Thank you for your response. I got a notification of your reply to this topic at my new email address. So, I think it has taken effect.

I have subscribed to the Journal/Newsletter and the Tuesday(?) emails about Book Promotions. I do not get any other emails from the 'Ranch.


Thanks,
-GB.

Site Managers,

I changed the email address in my profile a while back. But, I still get JavaRanch email (about the Book Promos and the Journal/Newsletter) at my old email address.

How long will it take for the email change in the profile to take effect?

Thanks,
-GB.

Thanks Nagaraju..
I do not have access to the Admin console, and will look up more on this.
-GB.

Hello folks,
Can a standalone WAR be installed in WAS 5.0?
The WAR is not part of any EAR. Is it possible to install it? Should an EAR be installed for a WAR to be installed successfully.
I appreciate all inputs.
-GB.

1. The command line tools "get" and "pcli" should be in the PATH environmental variable.
2. Use the optional ANT task pvcs as described in ANT's documentation
-GB.

I suspect that the version string is not valid. Can you check what error messages are logged to the console?
-GB.

A possible explanation :
Does the attribute "version" of "j2se" element have a restricting version specified?
Say, if the client has JRE 1.2 and JRE 1.4.2 installed, and the version attribute's value is "1.2", the 1.2's rt.jar is used, instead of 1.4.2's.
-GB.

I think it is an excellent situation wherein the adoption of a rule engine would do good. Check out a Javaranch's bartender's book - Jess In Action.
If you think a rule engine is too general, and are adventerous, you could come up with your own expression/rule language tailored for your domain.
-GB.

Originally posted by Jim Yingst:
[damian]: I know that I could access the path as well as the filename of the class I choose from the FileChoser. I could then find the package name from the path if I knew the start of the package.
It may be awkward, but this sounds like your best bet. Let's say the complete path is
/foo/bar/baz/a/b/c/MyClass.class
I'd try these in succession:
Class.forName("MyClass")
Class.forName("c.MyClass")
Class.forName("b.c.MyClass")
Class.forName("a.b.c.MyClass")
Class.forName("baz.a.b.c.MyClass")
Class.forName("bar.baz.a.b.c.MyClass")
Class.forName("foo.bar.baz.a.b.c.MyClass")
The first one of these that returns != null, that's your class.

Or... you can write your own class loader (or use URLClassLoader), and load the class file selected by the user. Once this is loaded, you can use reflection to find the package the class is in, or do whatever else you'd want to do with it.
-GB.

A possibility -
If server2 supports the telnet protocol, open a telnet session from servlet1 in server1 (or a helper class thereof) and execute the process in server2.

-GB.

Originally posted by Joel McNary:

<snipped />
Gopi, I'm not sure what you did wrong, but We get different results for a 6-card deck with a cut of 3:
<snipped />
Your top and bottom cards never change; you are dropping the bottom card from the bottom stack first (as opposed to the bottom card from the top stack)

Ahh.. I see. This is something that should be pretty easy to change in the code.. Perhaps, after the change, you can use this code to confirm the working of your solution.
The approach of your solution is noble. I have read your explanation.. yet to read the code.
-GB.

Did not find time to confirm the validity of the results.. but, anyway, here is my code.
Card.java
package cards; class Card { static final int HC_MN = 250394; final int id; Card(int id) { this.id = id; } int getId() { return id; } public String toString() { return "Card-" + id + "."; } public boolean equals(Object obj) { try { Card c = (Card)obj; return this.equals(c); } catch (ClassCastException cce) { return false; } return false; } public boolean equals(Card c){ return (c.id == this.id); } public int hashCode() { return Card.HC_MN + id; } } // end of class Card
CardFacory.java
package cards; class CardFactory { static Card createCard(int i) { return new Card(i); } }
CardStack.java
package cards; import java.util.Iterator; import java.util.LinkedHashSet; import java.util.Set; import java.util.Stack; class CardStack { protected Stack cards; protected int size; CardStack(int size){ cards = new Stack(); this.size = size; } void placeCard(Card card) { if (cards.size() == size) throw new RuntimeException("cards.CardStack.addCard:stack is full at " + size + " cards."); cards.push(card); } int size() { return size; } Card get(int pos) { return (Card)cards.get(pos - 1); } String showDeck() { StringBuffer rsb = new StringBuffer().append("Deck(").append(size).append(")-"); Iterator cIt = cards.iterator(); while (cIt.hasNext()) { rsb.append(((Card)cIt.next()).getId()).append(", "); } return rsb.substring(0, rsb.length() - 2).toString(); } }
Dealer.java
package cards; class Dealer { private static int vdSize; static CardStack[] cut(CardStack deck, int cSize) { if (cSize > deck.size()) throw new RuntimeException("cards.Dealer.cut: cut size cannot be more than deck size."); CardStack top = new CardStack(cSize); for (int ctr = 1; ctr <= cSize; ctr++) { top.placeCard(deck.get(ctr)); } CardStack bottom = new CardStack(deck.size() - cSize); for (int ctr = cSize + 1; ctr <= deck.size(); ctr++) { bottom.placeCard(deck.get(ctr)); } return new CardStack[] {top, bottom}; } // end of method cut static CardStack perfectShuffle(CardStack one, CardStack two) { CardStack sDeck = new CardStack(one.size() + two.size()); CardStack bottom, top = null; if (one.size() <= two.size()) { bottom = one; top = two; } else { bottom = two; top = one; } for (int ctr = 1; ctr <= bottom.size(); ctr++) { sDeck.placeCard(bottom.get(ctr)); sDeck.placeCard(top.get(ctr)); } for (int ctr = bottom.size() + 1; ctr <= top.size(); ctr++) { sDeck.placeCard(top.get(ctr)); } one = two = top = bottom = null; return sDeck; } static CardStack openNewDeck(int nCards) { CardStack vd = new CardStack(nCards); for (int ctr = 1; ctr <= nCards; ctr++) { vd.placeCard(CardFactory.createCard(ctr)); } vdSize = nCards; return vd; } // end of method openNewDeck static boolean attainedOriginality(CardStack stack) { if (vdSize != stack.size()) return false; for (int ctr = 1; ctr <= vdSize; ctr++) { if (ctr != ((Card)stack.get(ctr)).getId() ) return false; } return true; } } // end of class Dealer
PerfectCut.java
package cards; import java.util.LinkedHashSet; import java.util.Set; public class PerfectCut { // Private constants private static final int DEFAULT_N_CARDS = 10; private static final int DEFAULT_I_CUT = 5; // Private members. private static void print(String s) { System.out.println(s); } private static void print(long l) { print("" + l); } private static void print(boolean b) { print("" + b); } // Public members. public static void main(String[] args) { print("PerfectCut Started"); int nCards = DEFAULT_N_CARDS; int iCut = DEFAULT_I_CUT; if (args.length == 2) { try { nCards = Integer.parseInt(args[0]); iCut = Integer.parseInt(args[1]); } catch (NumberFormatException nfe) { print("Using default values"); nCards = DEFAULT_N_CARDS; iCut = DEFAULT_N_CARDS; } } print("nCards = " + nCards + ", iCut = " + iCut); print("Perfect shuffles needed = " + shuffles(nCards, iCut)); } // end of method main public static long shuffles(int nCards, int iCut) { long nShuffles = 0; CardStack vd = Dealer.openNewDeck(nCards); CardStack[] stacks = Dealer.cut(vd, iCut); print("Cut into two stacks of size " + stacks[0].size() + " and " + stacks[1].size()); CardStack sDeck = Dealer.perfectShuffle(stacks[0], stacks[1]); nShuffles = 1; while (! Dealer.attainedOriginality(sDeck)) { stacks = Dealer.cut(sDeck, iCut); sDeck = Dealer.perfectShuffle(stacks[0], stacks[1]); //print(sDeck.showDeck()); // uncomment to see card stacks nShuffles++; } return nShuffles; } } // end of class PerfectCut
Please comment.
-GB.

Originally posted by RArun Kumar:
What is the result for shuffles(1002,101).I am unable to find the result for shuffles(1002, 101). It runs for hours. Can anyone tell the algorithm to solve this problem. Any help is appreciated.
Thanks,
Arun

I wrote a small set of classes.. and got the answer as 66.
I got the answer within ~10 seconds..
Can anybody confirm the correctness of this answer? I will post the code after I find time to confirm it myself. (I tried a few other combinations.. 66 is the max answer I get..)
P.S. : I did not use any fancy algorithm - just brute force.
-GB.
[ June 19, 2003: Message edited by: Gopi Balaji ]

'int's and 'double's are not objects, and it is difficult/convoluted to apply Object-Oriented design patterns here. If you use their object wrappers (Integer, Double) instead, this is an excellent candidate for Strategy.
You can even have ComplexFloat, ComplexShort if has any meaning.
The Visitor pattern has too many disadvantages to be used casually.
-GB.

Originally posted by Ilja Preuss:

That link doesn't seem to work
And I don't understand why you'd need Singleton here - it seems to me as if AbstractFactory would totally suffice (and be more flexible).

Its strange.. the link as quoted in your post works, but not in my original..
Well, in the instance quoted here, it is an AbstractFactory. The Singleton pattern is superimposed on it, to ensure that there exists one and only one instance of the AbstractFactory, or any one of its children.
If the AbstractFactory, and its mutliple ConcreteFactory classes were not Singletons, then they could be instantiated at will. You would not want this, if you want the user to use only a specific and particular child of the AbstractFactory.
On the other hand, if you force all your programmers to instantiate only a particular child (say either declaratively like use.factory.implemntation=USAVehicleFactory, using a properties file, or hard-coding it like USAVehicleFactory.getInstance()), then you would tightly couple (degrees vary on method chosen) your code to that particular implementation of the factory.
The clients of the AbstractFactory interface are aware only of that class. They have no compile time dependency on the children of AbstractFactory. As described in that example, the source for the child of AbstractFactory class did not even exist when the client was coded and even shipped.
Using the AbstractFactory pattern here allows you to switch the factory implementation to create different products. Using the Singleton pattern here allows you to remove the client's compile time dependency on the implementation.
-GB.