[java] MySQL and java Queries (ho ho)
Author
right im doing a scrabble game and i need to perform queries on a database of some sort to check that the words are legit. I downloaded a dictionary that someone pointed me to but i haven't really got the faintest idea how to go about creating and utilising a database. ( i do know how to perform queries in mysql) but have no other knowledge on how to set one up and connect to it
many thanks
Author
ok i read through that but im still not 100% about actually creating the database itself (probably the wrong forum :/) but i figured someone would know how to? i have mysql server running if thats any help
The MySQL manual should be able to help you through most of the setup you need to do. If you just want a quick set of examples this is what I used for one of my apps: db.sql.
I also have some Java code DBManager.java which is fairly generic and you can adapt it for your use if you like. I suggest looking over the tutorial posted above first.
Edit:
If you're on unix you can just run one of the scripts like this 'mysql < db.sql'. I'm not sure about how the windows version works but I'd assume there's a similar command line client.
I also have some Java code DBManager.java which is fairly generic and you can adapt it for your use if you like. I suggest looking over the tutorial posted above first.
Edit:
If you're on unix you can just run one of the scripts like this 'mysql < db.sql'. I'm not sure about how the windows version works but I'd assume there's a similar command line client.
Here's 2 java classes I started recently. One class handles the connection to the database and retrieving results, the other classes just displays the data in a jtable.
download
download
Here's about the simplest possible way to accomplish this without MySQL. I just stuck all the words in a Hashtable. It takes a few seconds to construct the Hashtable, but checks are incredibly fast.
[Edited by - Kevinator on April 26, 2005 8:51:25 PM]
package driver;import java.io.*;import java.util.*;public class Driver { public static void main(String[] args) { System.out.print("Loading . . . "); BufferedReader br; // construct a new hashtable // this will be your "database" of legal words // string hashing functions are very effective, and // lookup times will be O(1). Hashtable table = new Hashtable(); // read in the list of legal words from a file // there are some good files at http://wordlist.sourceforge.net/ // you can use for this try { br = new BufferedReader(new FileReader("C:\\eclipse\\workspace\\stuff\\driver\\wordlist.dat")); String line = ""; while((line = br.readLine()) != null) { StringTokenizer tokenizer = new StringTokenizer(line, " ", false); line = tokenizer.nextToken(); table.put(line, line); } } catch(IOException e) { System.out.print(e); } System.out.print("done.\n"); br = new BufferedReader(new InputStreamReader(System.in)); String cont = "yes"; // ask a user to enter a word // program will inform the user whether or not the word is legal while(cont.equalsIgnoreCase("y") || cont.equalsIgnoreCase("yes")) { System.out.print("Type in a word to see if it exists: "); String word = ""; try { word = new String(br.readLine()); } catch(Exception e) { System.out.print(e); } // this is where you look to see if the word is // in the hashtable String result = (String)table.get(word); if(result != null) System.out.print("Result: \"" + result + "\" exists in database.\nAgain? "); else System.out.print("Result: \"" + word + "\" doesn't exist in database.\nAgain? "); try { cont = new String(br.readLine()); } catch(IOException e) { System.out.print(e); } } }}[Edited by - Kevinator on April 26, 2005 8:51:25 PM]
I recommend using a dictionary file or files rather than an SQL database.
Unless your dictionary file is very large, you can just read the words into memory and stick them in a HashMap (don't use Hashtable).
Jon
Unless your dictionary file is very large, you can just read the words into memory and stick them in a HashMap (don't use Hashtable).
Jon
Quote:Original post by TomButcher
so you're saying a hash map would be more efficient?
Yes. If I remember rightly Hashtables are thread safe (synchonized), which means they can handle being accessed by multiple threads at one time. However, this has a performance cost, and you don't really need the Hashtable to be synchronised in a scrabble game (I assume). This is unlike the rest of the Collections framework, which doesnt as a rule contain synchronized classes - you have to do the synchronization yourself normally.
If you really need a HashMap to handle access by multiple threads you should use ConcurrentHashMap (which synchronizes at the bucket level, rather than the whole collection) - I can point you at the code for the class if you need it.
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