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• Using RecordStore in Java J2ME

  - by me123

  Hi, I am currently doing some J2ME development. I am having a problem in that a user can add and remove elements to the record store, and if a record gets deleted, then that record is left empty and the others don't move up one. I'm trying to come up with a loop that will check if a record has anything in it (incase it has been deleted) and if it does then I want to add the contents of that record to a list. My code is similar to as follows: for (int i = 1; i <= rs.getNumRecords(); i++) { // Re-allocate if necessary if (rs.getRecordSize(i) > recData.length) recData = new byte[rs.getRecordSize(i)]; len = rs.getRecord(i, recData, 0); st = new String(recData, 0, len); System.out.println("Record #" + i + ": " + new String(recData, 0, len)); System.out.println("------------------------------"); if(st != null) { list.insert(i-1, st, null); } } When it gets to rs.getRecordSize(i), I always get a "javax.microedition.rms.InvalidRecordIDException: error finding record". I know this is due to the record being empty but I can't think of a way to get around this problem. Any help would be much appreciated. Thanks in advance.

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• java time check API

  - by ring bearer

  I am sure this was done 1000 times in 1000 different places. The question is I want to know if there is a better/standard/faster way to check if current "time" is between two time values given in hh:mm:ss format. For example, my big business logic should not run between 18:00:00 and 18:30:00. So here is what I had in mind: public static boolean isCurrentTimeBetween(String starthhmmss, String endhhmmss) throws ParseException{ DateFormat hhmmssFormat = new SimpleDateFormat("yyyyMMddhh:mm:ss"); Date now = new Date(); String yyyMMdd = hhmmssFormat.format(now).substring(0, 8); return(hhmmssFormat.parse(yyyMMdd+starthhmmss).before(now) && hhmmssFormat.parse(yyyMMdd+endhhmmss).after(now)); } Example test case: String doNotRunBetween="18:00:00,18:30:00";//read from props file String[] hhmmss = downTime.split(","); if(isCurrentTimeBetween(hhmmss[0], hhmmss[1])){ System.out.println("NOT OK TO RUN"); }else{ System.out.println("OK TO RUN"); } What I am looking for is code that is better in performance in looks in correctness What I am not looking for third-party libraries Exception handling debate variable naming conventions method modifier issues

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• What would you like to correct and/or improve in this java implementation of Chain Of Responsibility

  - by Maciek Kreft

  package design.pattern.behavioral; import design.pattern.behavioral.ChainOfResponsibility.*; public class ChainOfResponsibility { public static class Chain { private Request[] requests = null; private Handler[] handlers = null; public Chain(Handler[] handlers, Request[] requests){ this.handlers = handlers; this.requests = requests; } public void start() { for(Request r : requests) for (Handler h : handlers) if(h.handle(r)) break; } } public static class Request { private int value; public Request setValue(int value){ this.value = value; return this; } public int getValue() { return value; } } public static class Handler<T1> { private Lambda<T1> lambda = null; private Lambda<T1> command = null; public Handler(Lambda<T1> condition, Lambda<T1> command) { this.lambda = condition; this.command = command; } public boolean handle(T1 request) { if (lambda.lambda(request)) command.lambda(request); return lambda.lambda(request); } } public static abstract class Lambda<T1>{ public abstract Boolean lambda(T1 request); } } class TestChainOfResponsibility { public static void main(String[] args) { new TestChainOfResponsibility().test(); } private void test() { new Chain(new Handler[]{ // chain of responsibility new Handler<Request>( new Lambda<Request>(){ // command public Boolean lambda(Request condition) { return condition.getValue() >= 600; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are rich: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), new Handler<Request>( new Lambda<Request>(){ public Boolean lambda(Request condition) { return condition.getValue() >= 100; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are poor: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), }, new Request[]{ new Request().setValue(600), // chaining method new Request().setValue(100), } ).start(); } }

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• Comparable and Comparator contract with regards to null

  - by polygenelubricants

  Comparable contract specifies that e.compareTo(null) must throw NullPointerException. From the API: Note that null is not an instance of any class, and e.compareTo(null) should throw a NullPointerException even though e.equals(null) returns false. On the other hand, Comparator API mentions nothing about what needs to happen when comparing null. Consider the following attempt of a generic method that takes a Comparable, and return a Comparator for it that puts null as the minimum element. static <T extends Comparable<? super T>> Comparator<T> nullComparableComparator() { return new Comparator<T>() { @Override public int compare(T el1, T el2) { return el1 == null ? -1 : el2 == null ? +1 : el1.compareTo(el2); } }; } This allows us to do the following: List<Integer> numbers = new ArrayList<Integer>( Arrays.asList(3, 2, 1, null, null, 0) ); Comparator<Integer> numbersComp = nullComparableComparator(); Collections.sort(numbers, numbersComp); System.out.println(numbers); // "[null, null, 0, 1, 2, 3]" List<String> names = new ArrayList<String>( Arrays.asList("Bob", null, "Alice", "Carol") ); Comparator<String> namesComp = nullComparableComparator(); Collections.sort(names, namesComp); System.out.println(names); // "[null, Alice, Bob, Carol]" So the questions are: Is this an acceptable use of a Comparator, or is it violating an unwritten rule regarding comparing null and throwing NullPointerException? Is it ever a good idea to even have to sort a List containing null elements, or is that a sure sign of a design error?

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• how can I convert String to SecretKey

  - by Alaa

  I want to convert String to secretKey public void generateCode(String keyStr){ KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(128); // 192 and 256 bits may not be available // Generate the secret key specs. secretKey skey=keyStr; //How can I make the casting here //SecretKey skey = kgen.generateKey(); byte[] raw = skey.getEncoded(); } I try to use BASE64Decoder instead of secretKey, but I face a porblem which is I cannot specify key length. EDIT: I want to call this function from another place static public String encrypt(String message , String key , int keyLength) throws Exception { // Get the KeyGenerator KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(keyLength); // 192 and 256 bits may not be available // Generate the secret key specs. //decode the BASE64 coded message SecretKey skey = key; //here is the error raw = skey.getEncoded(); SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); // Instantiate the cipher Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); System.out.println("msg is" + message + "\n raw is" + raw); byte[] encrypted = cipher.doFinal(message.getBytes()); String cryptedValue = new String(encrypted); System.out.println("encrypted string: " + cryptedValue); return cryptedValue; } Any one can help, i'll be very thankful.

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• Get an Arduino and Android phone to communicate over the web

  - by Saleem

  I am writing an Android application to communicate with my Arduino over the web. The Arduino is running a web server through an Ethernet shield. I am attaching my code, but I will explain it here so you will understand what I am trying to do. The Android sends an HTTP request in the format http://192.168.1.148/?Lights=1. The Arduino gets the request, executes the command (in this case turning on some lights) and then responds to the Android device by simply sending the string "Lights=On". The Android will then change the color of the button to notify the user that the command was executed successfully. The Arduino is getting the instruction and executing it and sending the response but my button color is not changing. I know that the Android device is getting the string because I added a debug line to change the text on the button to the received response. The relevant code for the Android device is: ((Button) v).setText(sb.toString()); //This works and the button text changes to "Lights=On". //Test response and update button if(sb.toString()=="Lights=On"){ v.getBackground().setColorFilter(0xFFFFFF00, PorterDuff.Mode.MULTIPLY); Drawable d = lightOff.getBackground(); lightOff.invalidateDrawable(d); d.clearColorFilter(); } The Arduino code is: if(s=="Lights"){ switch(client.read()){ case '0': digitalWrite(LightPin,0); client.print("Lights=Off"); //debug Serial.println("Lights=Off"); break; case '1': digitalWrite(LightPin,1); client.print("Lights=On"); Serial.println("Lights=On"); break; } } Please let me know if you need more of the code to answer this question.

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• Can't read some attributes with SAX

  - by akappa

  Hi all, I'm trying to parse that document with SAX: <scxml version="1.0" initialstate="start" name="calc"> <datamodel> <data id="expr" expr="0" /> <data id="res" expr="0" /> </datamodel> <state id="start"> <transition event="OPER" target="opEntered" /> <transition event="DIGIT" target="operand" /> </state> <state id="operand"> <transition event="OPER" target="opEntered" /> <transition event="DIGIT" /> </state> </scxml> I read all the attributes well, except "initialstate" and "name"... I get the attributes with the startElement handler, but the size of the attribute list for scxml is zero. Why? How I can overcome that problem? Edit: public void startElement(String uri, String localName, String qName, Attributes attributes){ System.out.println(attributes.getValue("initialstate")); System.out.println(attributes.getValue("name")); } that, when parsing the first tag, doesn't work (prints "null" two times). In fact, attributes.getLength(); evaluates to zero. Thanks

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• Not able to compile ActionScript from Java SDK

  - by Heang S.

  I was reading the Flex Compiler API User Guide at http://livedocs.adobe.com/flex/3/compilerAPI_flex3.pdf and tried to follow the example to create a Java application to compile a Flex application. Here is my program: import flex2.tools.oem.Application; import java.io.*; public class MyAppCompiler { public static void main(String[] args) { try { Application application = new Application( new File("../apps/TestApp.mxml")); application.setOutput(new File("../apps/TestApp.swf")); long result = application.build(true); if (result 0) System.out.println("Compile Success"); else System.out.println("Compile Failed"); } catch (Exception ex){ ex.printStackTrace(); } } } Unfortunately, I get "java.lang.ExceptionInInitializerError" on the very first line. Internally, the error appears to be on the following line: Exception in thread "main" java.lang.ExceptionInInitializerError at myApps.MyAppCompiler.main(MyAppCompiler.java:9) Caused by: java.lang.NullPointerException at flex2.tools.oem.Application. (Application.java:184) I am using Eclipse 3.3. However, I see the problem when I run my program either from Eclipse or from a command line. Any suggestions would be greatly appreciated.

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• Cursor while loop returning every value but the last

  - by LordSnoutimus

  Hello, I am using a while loop to iterate through a cursor and then outputing the longitude and latitude values of every point within the database. For some reason it is not returning the last (or first depending on if I use Cursor.MoveToLast) set of longitude and latitude values in the cursor. Here is my code: public void loadTrack() { SQLiteDatabase db1 = waypoints.getWritableDatabase(); Cursor trackCursor = db1.query(TABLE_NAME, FROM, "trackidfk=1", null, null, null,ORDER_BY); trackCursor.moveToFirst(); while (trackCursor.moveToNext()) { Double lat = trackCursor.getDouble(2); Double lon = trackCursor.getDouble(1); //overlay.addGeoPoint( new GeoPoint( (int)(lat*1E6), (int)(lon*1E6))); System.out.println(lon); System.out.println(lat); } } From this I am getting: 04-02 15:39:07.416: INFO/System.out(10551): 3.0 04-02 15:39:07.416: INFO/System.out(10551): 5.0 04-02 15:39:07.416: INFO/System.out(10551): 4.0 04-02 15:39:07.416: INFO/System.out(10551): 5.0 04-02 15:39:07.416: INFO/System.out(10551): 5.0 04-02 15:39:07.416: INFO/System.out(10551): 5.0 04-02 15:39:07.416: INFO/System.out(10551): 4.0 04-02 15:39:07.416: INFO/System.out(10551): 4.0 04-02 15:39:07.416: INFO/System.out(10551): 3.0 04-02 15:39:07.416: INFO/System.out(10551): 3.0 04-02 15:39:07.416: INFO/System.out(10551): 2.0 04-02 15:39:07.416: INFO/System.out(10551): 2.0 04-02 15:39:07.493: INFO/System.out(10551): 1.0 04-02 15:39:07.493: INFO/System.out(10551): 1.0 7 Sets of values, where I should be getting 8 sets. Thanks.

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• help with javamail api

  - by bobby

  import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import javax.mail.*; import javax.mail.internet.*; import javax.mail.event.*; import java.net.*; import java.util.*; public class servletmail extends HttpServlet { public void doPost(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException { PrintWriter out=response.getWriter(); response.setContentType("text/html"); try { Properties props=new Properties(); props.put("mail.transport.protocol", "smtp"); props.put("mail.smtp.host","smtp.gmail.com"); props.put("mail.smtp.port", "25"); props.put("mail.smtp.auth", "true"); Authenticator authenticator = new Authenticator() { protected PasswordAuthentication getPasswordAuthentication() { return new PasswordAuthentication("user", "pass"); } }; Session sess=Session.getDefaultInstance(props,authenticator); Message msg=new MimeMessage(sess); msg.setFrom(new InternetAddress("[email protected]")); msg.addRecipient(Message.RecipientType.TO, new InternetAddress("[email protected]")); msg.setSubject("Hello JavaMail"); msg.setText("Welcome to JavaMail"); Transport.send(msg); out.println("mail has been sent"); } catch(Exception e) { System.out.println("err"+e); } } } im working with above im gettin d following error servletmail.java:22: reference to Authenticator is ambiguous, both class java.ne t.Authenticator in java.net and class javax.mail.Authenticator in javax.mail mat ch Authenticator authenticator = new Authenticator() ^ servletmail.java:22: reference to Authenticator is ambiguous, both class java.ne t.Authenticator in java.net and class javax.mail.Authenticator in javax.mail mat ch Authenticator authenticator = new Authenticator() ^ 2 errors i have followed the example in http://java.sun.com/developer/onlineTraining/JavaMail/contents.html how should i get the output..will the above code...work what are the changes that need to be made..im using thunderbird smtp server

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• Get Last Friday of Month in Java

  - by Nick Klauer

  I am working on a project where the requirement is to have a date calculated as being the last Friday of a given month. I think I have a solution that only uses standard Java, but I was wondering if anyone knew of anything more concise or efficient. Below is what I tested with for this year: for (int month = 0; month < 13; month++) { GregorianCalendar d = new GregorianCalendar(); d.set(d.MONTH, month); System.out.println("Last Week of Month in " + d.getDisplayName(d.MONTH, Calendar.LONG, Locale.ENGLISH) + ": " + d.getLeastMaximum(d.WEEK_OF_MONTH)); d.set(d.DAY_OF_WEEK, d.FRIDAY); d.set(d.WEEK_OF_MONTH, d.getActualMaximum(d.WEEK_OF_MONTH)); while (d.get(d.MONTH) > month || d.get(d.MONTH) < month) { d.add(d.WEEK_OF_MONTH, -1); } Date dt = d.getTime(); System.out.println("Last Friday of Last Week in " + d.getDisplayName(d.MONTH, Calendar.LONG, Locale.ENGLISH) + ": " + dt.toString()); }

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• can i use javabeans with hibernate ?

  - by Dilllllo

  Hello i'm using a plugin of hibernate2 in my webproject with jsp ,in my project i have a register page. Can i use javabeans to send information from a html <form> using hibernate class's ? with out hibernate i creat class with get and set like that package com.java2s; public class Lang { private String choix; private String comm; public String getChoix() { return choix; } public void setChoix(String choix) { this.choix = choix; //System.out.println(choix); } public String getComm() { return comm; } public void setComm(String comm) { this.comm = comm; // System.out.println(comm); } } but i know that hibernate generate a get and set class ! and recive it with that : <jsp:useBean id='user' class='com.java2s.Lang' type='com.java2s.Lang' scope='session' /> <jsp:setProperty name='user' property='*'/> any idea how to do that ?

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• Working with mongodb from Java

  - by demas

  I have launch mongodb server: [[email protected]][~]% mongod --dbpatmongod --dbpath /home/demas/temp/ Mon Apr 19 09:44:18 Mongo DB : starting : pid = 4538 port = 27017 dbpath = /home/demas/temp/ master = 0 slave = 0 32-bit ** NOTE: when using MongoDB 32 bit, you are limited to about 2 gigabytes of data ** see http://blog.mongodb.org/post/137788967/32-bit-limitations for more Mon Apr 19 09:44:18 db version v1.4.0, pdfile version 4.5 Mon Apr 19 09:44:18 git version: nogitversion Mon Apr 19 09:44:18 sys info: Linux arch.local.net 2.6.33-ARCH #1 SMP PREEMPT Mon Apr 5 05:57:38 UTC 2010 i686 BOOST_LIB_VERSION=1_41 Mon Apr 19 09:44:18 waiting for connections on port 27017 Mon Apr 19 09:44:18 web admin interface listening on port 28017 I have created documents by console client: [[email protected]][~]% mongo MongoDB shell version: 1.4.0 url: test connecting to: test type "help" for help > db.some.find(); { "_id" : ObjectId("4bcbef3c3be43e9b7e04ef3d"), "name" : "mongo" } { "_id" : ObjectId("4bcbef423be43e9b7e04ef3e"), "x" : 3 } Now I am trying to work with MongoDb from Java: import com.mongodb.*; import java.net.UnknownHostException; public class test1 { public static void main(String[] args) { System.out.println("Start"); try { Mongo m = new Mongo("localhost", 27017); DB db = m.getDB("test"); DBCollection coll = db.getCollection("some"); coll.insert(makeDocument(10, "James", "male")); System.out.println("Finish"); } catch (UnknownHostException ex) { ex.printStackTrace(); } catch (MongoException ex) { ex.printStackTrace(); } } public static BasicDBObject makeDocument(int id, String name, String gender) { BasicDBObject doc = new BasicDBObject(); doc.put("id", id); doc.put("name", name); doc.put("gender", gender); return doc; } } But execution stops on line coll.insert(): [[email protected]][~/dev/study/java/mongodb]% javac test1.java [[email protected]][~/dev/study/java/mongodb]% java test1 Start There are not messages from mogodb server regarding accepted connection. Why?

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• What is default javac source mode (assert as identifier compilation)?

  - by waste

  According to Orcale's Java7 assert guide: source mode 1.3 (default) — the compiler accepts programs that use assert as an identifier, but issues warnings. In this mode, programs are not permitted to use the assert statement. source mode 1.4 — the compiler generates an error message if the program uses assert as an identifier. In this mode, programs are permitted to use the assert statement. I wrote such class: package mm; public class ClassTest { public static void main(String[] arg) { int assert = 1; System.out.println(assert); } } It should compile fine if Oracle's info right (1.3 is default source mode). But I got errors like this: $ javac -version javac 1.7.0_04 $ javac -d bin src/mm/* src\mm\ClassTest.java:5: error: as of release 1.4, 'assert' is a keyword, and may not be used as an identifier int assert = 1; ^ (use -source 1.3 or lower to use 'assert' as an identifier) src\mm\ClassTest.java:6: error: as of release 1.4, 'assert' is a keyword, and may not be used as an identifier System.out.println(assert); ^ (use -source 1.3 or lower to use 'assert' as an identifier) 2 errors I added manually -source 1.3 and it issued warnings but compiled fine. It seems that Oracle's information is wrong and 1.3 is not default source mode. Which one is it then?

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• puzzled with java if else performance

  - by user1906966

  I am doing an investigation on a method's performance and finally identified the overhead was caused by the "else" portion of the if else statement. I have written a small program to illustrate the performance difference even when the else portion of the code never gets executed: public class TestIfPerf { public static void main( String[] args ) { boolean condition = true; long time = 0L; int value = 0; // warm up test for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } // benchmark if condition only time = System.nanoTime(); for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } } time = System.nanoTime() - time; System.out.println( "1) performance " + time ); time = System.nanoTime(); // benchmark if else condition for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } time = System.nanoTime() - time; System.out.println( "2) performance " + time ); } } and run the test program with java -classpath . -Dmx=800m -Dms=800m TestIfPerf. I performed this on both Mac and Linux Java with 1.6 latest build. Consistently the first benchmark, without the else is much faster than the second benchmark with the else section even though the code is structured such that the else portion is never executed because of the condition. I understand that to some, the difference might not be significant but the relative performance difference is large. I wonder if anyone has any insight to this (or maybe there is something I did incorrectly). Linux benchmark (in nano) performance 1215488 performance 2629531 Mac benchmark (in nano) performance 1667000 performance 4208000

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• Noob question about a statement in a Java program

  - by happysoul

  I am beginner to java and was trying out this code puzzle from the book head first java which I solved as follows and got the output correct :D class DrumKit { boolean topHat=true; boolean snare=true; void playSnare() { System.out.println("bang bang ba-bang"); } void playTopHat() { System.out.println("ding ding da-ding"); } } public class DrumKitTestDriver { public static void main(String[] args) { DrumKit d =new DrumKit(); if(d.snare==true) { d.playSnare(); } d.playTopHat(); } } Output is :: bang bang ba-bang ding ding da-ding Now the problem is that in that code puzzle one code snippet is left that I did not include..it's as follows d.snare=false; Even though I did not write it , I got the output like the book. I am wondering why is there need for us to set it's value as false even when we know the code is gonna run without it too !?? I am wondering what the coder had in mind ..I mean what could be the possible future use and motive behind doing this ? I am sorry if it's a dumb question. I just wanna know why or why not to include that particular statement ? It's not like there's a loop or something that we need to come out of. Why is that statement there ?

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• call lynx from jsp script

  - by Piero

  Hi, I have an execute(String cmd) in a jsp script that calls the exec method from the Runtime class. It works when I call a local command, like a php script stored on the server. for example: /usr/bin/php /path/to/php/script arg1 arg2 So I guess my execute command is ok, since it is working with that. Now when I try to call lynx, the text-based web browser, it does not work. If I call it in a terminal, it works fine: /usr/bin/lynx -dump -accept_all_cookies 'http://www.someurl.net/?arg1=1&arg2=2' But when I call this from my execute command, nothing happens... Any idea why? This is my execute method: public String execute(String cmd){ Runtime r = Runtime.getRuntime(); Process p = null; String res = ""; try { p = r.exec(cmd); InputStreamReader isr = new InputStreamReader(p.getInputStream()); BufferedReader br = new BufferedReader(isr); String line = null; //out.println(res); while ((line = br.readLine()) != null) { res += line; } p.waitFor(); } catch (Exception e) { res += e; } System.out.println(p.exitValue()); return res; }

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• java connectivity with mysql error

  - by abson

  I just started with the connectivity and tried this example. I have installed the necessary softwares. Also copied the jar file into the /ext folder.Yet the code below has the following error import java.sql.*; public class Jdbc00 { public static void main(String args[]){ try { Statement stmt; Class.forName("com.mysql.jdbc.Driver"); String url = "jdbc:mysql://localhost:3306/mysql" DriverManager.getConnection(url,"root", "root"); //Display URL and connection information System.out.println("URL: " + url); System.out.println("Connection: " + con); //Get a Statement object stmt = con.createStatement(); //Create the new database stmt.executeUpdate( "CREATE DATABASE JunkDB"); stmt.executeUpdate( "GRANT SELECT,INSERT,UPDATE,DELETE," + "CREATE,DROP " + "ON JunkDB.* TO 'auser'@'localhost' " + "IDENTIFIED BY 'drowssap';"); con.close(); }catch( Exception e ) { e.printStackTrace(); }//end catch }//end main }//end class Jdbc00 But it gave the following error D:\Java12\Explore>java Jdbc00 java.lang.ClassNotFoundException: com.mysql.jdbc.Driver at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Unknown Source) at Jdbc11.main(Jdbc00.java:11) Could anyone please guide me in correcting this?

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• [Java] Nested methods vs "piped" methods, which is better?

  - by Michael Mao

  Hi: Since uni, I've programming in Java for 3 years, although I am not fully dedicated to this language, I have spent quite some time in it, nevertheless. I understand both ways, just curious which style do you prefer. public class Test{ public static void main(String[] args) { System.out.println(getAgent().getAgentName()); } private static Agent getAgent() { return new Agent(); }} class Agent{ private String getAgentName() { return "John Smith"; }} I am pretty happy with nested method calls such like the following public class Test{ public static void main(String[] args) { getAgentName(getAgent()); } private static void getAgentName(Agent agent) { System.out.println(agent.getName()); } private static Agent getAgent() { return new Agent(); }} class Agent { public String getName(){ return "John Smith"; }} They have identical output I saw "John Smith" twice. I wonder, if one way of doing this has better performance or other advantages over the other. Personally I prefer the latter, since for nested methods I can certainly tell which starts first, and which is after. The above code is but a sample, The code that I am working with now is much more complicated, a bit like a maze... So switching between the two styles often blows my head in no time.

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• Printing a sideways triangle in java

  - by Will

  I'm trying to print a sideways triangle in java. If the user enters 5, the output should be: * *** ***** *** * If the user enters 6, the output should be: * *** ***** ***** *** * I've gotten it to work for the case when the user enters 5, 3, or 1 but my code seems to work for those three cases only. I was wondering if anyone could help me get my code working for more cases. Here it is: public void printArrow( int n ) { int asterisks = 1; for ( int i = 0; i <= n/2; i++ ) { for ( int j = i; j < asterisks; j++ ) { System.out.print( "*" ); } asterisks += 3; System.out.println(); } asterisks = asterisks / 2 - 2; for ( int i = 0; i < n/2; i++ ) { for ( int k = i; k < asterisks; k++ ) { System.out.print( "*" ); } if ( i == 1 ) { System.out.print( "*" ); } asterisks -= 2; System.out.println(); } }

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• Grails UrlMappings with .html

  - by Glennn

  I'm developing a Grails web application (mainly as a learning exercise). I have previously written some standard Grails apps, but in this case I wanted to try creating a controller that would intercept all requests (including static html) of the form: <a href="/testApp/testJsp.jsp">test 1</a> <a href="/testApp/testGsp.gsp">test 2</a> <a href="/testApp/testHtm.htm">test 3</a> <a href="/testApp/testHtml.html">test 4</a> The intent is to do some simple business logic (auditing) each time a user clicks a link. I know I could do this using a Filter (or a range of other methods), however I thought this should work too and wanted to do this using a Grails framework. I set up the Grail UrlMappings.groovy file to map all URLs of that form (/$myPathParam?) to a single controller: class UrlMappings { static mappings = { "/$controller/$action?/$id?"{ constraints { } } "/$path?" (controller: 'auditRecord', action: 'showPage') "500"(view:'/error') } } In that controller (in the appropriate "showPage" action) I've been printing out the path information, for example: def showPage = { println "params.path = " + params.path ... render(view: resultingView) } The results of the println in the showPage action for each of my four links are testJsp.jsp testGsp.gsp testHtm.htm testHtml Why is the last one "testHtml", not "testHtml.html"? In a previous (Stack Overflow query) Olexandr encountered this issue and was advised to simply concatenate the value of request.format - which, indeed, does return "html". However request.format also returns "html" for all four links. I'm interested in gaining an understanding of what Grails is doing and why. Is there some way to configure Grails so the params.path variable in the controller shows "testHtml.html" rather than stripping off the "html" extension? It doesn't seem to remove the extension for any other file type (including .htm). Is there a good reason it's doing this? I know that it is a bit unusual to use a controller for static html, but still would like to understand what's going on.

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• How should I read from a buffered reader?

  - by Roman

  I have the following example of reading from a buffered reader: while ((inputLine = input.readLine()) != null) { System.out.println("I got a message from a client: " + inputLine); } The code in the loop println will be executed whenever something appears in the buffered reader (input in this case). In my case, if a client-application writes something to the socket, the code in the loop (in the server-application) will be executed. But I do not understand how it works. inputLine = input.readLine() waits until something appears in the buffered reader and when something appears there it returns true and the code in the loop is executed. But when null can be returned. There is another question. The above code was taken from a method which throws Exception and I use this code in the run method of the Thread. And when I try to put throws Exception before the run the compiler complains: overridden method does not throw exception. Without the throws exception I have another complain from the compiler: unreported exception. So, what can I do?

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• JPanel.addComponentListener does not work when the listener is a class variable

  - by Coder

  I have a public class which has the following method and instance variable: public void setImagePanel(JPanel value) { imagePanel = value; if (imagePanel != null) { //method 1 : works imagePanel.addComponentListener(new ComponentAdapter() { public void componentResized(ComponentEvent evt) { System.out.println("Here 1"); } }); //method 2 : does not work panelResizeListener = new ResizeListener(); imagePanel.addComponentListener(panelResizeListener); //method 3 : works //ResizeListener listener = new ResizeListener(); //imagePanel.addComponentListener(listener); //method 4 : works //imagePanel.addComponentListener(new ResizeListener()); //method 5 : does not work -- THIS IS THE DESIRED CODE I WANT TO USE imagePanel.addComponentListener(panelResizeListener); } } public class ResizeListener extends ComponentAdapter { @Override public void componentResized(ComponentEvent evt) { System.out.println("RESIZE 3"); } } private ResizeListener panelResizeListener = new ResizeListener(); Each of the methods above correspond the to code immediately below until the next //method comment. What i don't understand is why i can't use the class instance variable and add that to the JPanel as a component listener. What happens in the cases above where i say that the method does not work is that i don't get the "RESIZE 3" log messages. In all cases where i list that it works, then i get the "RESIZE 3" messages. The outer class is public with no other modification except that it implements an interface that i created (which has no methods or variables in common with the methods and variables listed above). If anyone can help me i would greatly appreciate it. This problem makes no sense to me, the code should be identical.

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• How can i setParth for new File use JFilechose , save dialog ?

  - by tiendv

  I have a dialog use Jfilechose, when i save a file by use FileOutputStream to create a file.txt to save in path which user want . But i have problem that it alway save in c:/user/Document Check my code DownLoadDialog downloadDialog = new DownLoadDialog(); int result = downloadDialog.showSaveDialog(queryPanel); if(result == downloadDialog.APPROVE_OPTION) { File file = downloadDialog.getSelectedFile(); //String parth =file.getPath(); //System.out.println(parth); //if(file.exists()) { // int response = JOptionPane.showConfirmDialog (null,"Overwrite existing file?","Confirm Overwrite",JOptionPane.OK_CANCEL_OPTION,JOptionPane.QUESTION_MESSAGE); // if(response == JOptionPane.OK_OPTION) {} //} else { if(resultGoogleSearch > 0) { { String parth = new File(downloadDialog.getSelectedFile().getAbsolutePath().concat(".txt")).toString(); System.out.println(parth); for(int i=0;i<resultGoogleSearch;i++) { String[] temp = googleSearchResult.get(i).split("<br>"); //String resultURL = temp[0]; //File dir = downloadDialog.getCurrentDirectory(); try{ FileOutputStream googleReuslt = new FileOutputStream( downloadDialog.getSelectedFile().getAbsolutePath()+".txt" ); OutputStreamWriter writer = new OutputStreamWriter(googleReuslt); BufferedWriter buffer = new BufferedWriter(writer); writer.write(temp[0]); writer.close(); buffer.close(); } catch (FileNotFoundException fEx){ } catch(IOException ioEx) { } } } JOptionPane.showMessageDialog(IDRSApplication.idrsJFrame, IDRSResourceBundle.res.getString("successful")); } problem is here : why can't i set parth for new file ? FileOutputStream googleReuslt = new FileOutputStream( downloadDialog.getSelectedFile().getAbsolutePath()+".txt" ); OutputStreamWriter writer = new OutputStreamWriter(googleReuslt); BufferedWriter buffer = new BufferedWriter(writer); writer.write(temp[0]); writer.close(); buffer.close();

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• Getting size of a specific byte array from an array of pointers to bytes

  - by Pat James

  In the following example c code, used in an Arduino project, I am looking for the ability to get the size of a specific byte array within an array of pointers to bytes, for example void setup() { Serial.begin(9600); // for debugging byte zero[] = {8, 169, 8, 128, 2,171,145,155,141,177,187,187,2,152,2,8,134,199}; byte one[] = {8, 179, 138, 138, 177 ,2,146, 8, 134, 8, 194,2,1,14,199,7, 145, 8,131, 8,158,8,187,187,191}; byte two[] = {29,7,1,8, 169, 8, 128, 2,171,145,155,141,177,187,187,2,152,2,8,134,199, 2, 2, 8, 179, 138, 138, 177 ,2,146, 8, 134, 8, 194,2,1,14,199,7, 145, 8,131, 8,158,8,187,187,191}; byte* numbers[3] = {zero, one, two }; function(numbers[1], sizeof(numbers[1])/sizeof(byte)); //doesn't work as desired, always passes 2 as the length function(numbers[1], 25); //this works } void loop() { } void function( byte arr[], int len ) { Serial.print("length: "); Serial.println(len); for (int i=0; i<len; i++){ Serial.print("array element "); Serial.print(i); Serial.print(" has value "); Serial.println((int)arr[i]); } } In this code, I understand that sizeof(numbers1)/sizeof(byte)) doesn't work because numbers1 is a pointer and not the byte array value. Is there a way in this example that I can, at runtime, get at the length of a specific (runtime-determined) byte array within an array of pointers to bytes? Understand that I am limited to developing in c (or assembly) for an Arduino environment. Also open to other suggestions rather than the array of pointers to bytes. The overall objective is to organize lists of bytes which can be retrieved, with length, at runtime.

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