java-programmer >>arrays of generic types

arrays of generic types

Index ‹ java-programmer

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- 1
 - GUI and command lineHello,
 
 I need to connect my GUI program with a terminal in Linux (command
 line). The task is to input inside a textField the command to exectue as
 for exemple: "ls -al" or "gcc whatever.c -o whatever" but everything
 must be done by a GUI program.
 
 How can I call the terminal or execute these commands?
 
 thanks,
 
 Marcelo
- 1
 - Java Newbie Question: Character Sets, Unicode, et al [Long]Roedy Green wrote:
 > Ve need some definitions that make clear the distinction between:
 > an character set,
 > a character
 > a glyph
 > a font
 > an encoding.
 
 I'll take a stab at it.
 
 I decided to see what Unicode had to say on the matter. That seemed
 relevant, but may have been a mistake. In any event, here are some
 possibly relevant defintions from the Unicode 4.0 glossary
 (http://www.unicode.org/glossary/):
 
 ==== From the Unicode 4.0 Glossary ====
 
 Abstract Character. A unit of information used for the organization,
 control, or representation of textual data. (See Definition D3 in
 Section 3.3, Characters and Coded Representations .)
 
 Character. (1) The smallest component of written language that has
 semantic value; refers to the abstract meaning and/or shape, rather than
 a specific shape (see also glyph), though in code tables some form of
 visual representation is essential for the reader's understanding. (2)
 Synonym for abstract character. (See Definition D3 in Section 3.3,
 Characters and Coded Representations .) (3) The basic unit of encoding
 for the Unicode character encoding. (4) The English name for the
 ideographic written elements of Chinese origin. (See ideograph (2).)
 
 Character Encoding Form. Mapping from a character set definition to the
 actual code units used to represent the data.
 
 Character Encoding Scheme. A character encoding form plus byte
 serialization. There are seven character encoding schemes in Unicode:
 UTF-8, UTF-16, UTF-16BE, UTF-16LE, UTF-32, UTF-32BE and UTF-32LE.
 
 Character Set. A collection of elements used to represent textual
 information.
 
 Coded Character Set. A character set in which each character is assigned
 a numeric code point. Frequently abbreviated as character set, charset,
 or code set.
 
 Code Point. (1) A numerical index (or position) in an encoding table
 used for encoding characters. (2) Synonym for Unicode scalar value.
 
 Code Unit. The minimal bit combination that can represent a unit of
 encoded text for processing or interchange. (See Definition D5 in
 Section 3.3, Characters and Coded Representations .)
 
 Encoded Character. An abstract character together with its associated
 Unicode scalar value (code point). By itself, an abstract character has
 no numerical value, but the process of "encoding a character" associates
 a particular Unicode scalar value with a particular abstract character,
 thereby resulting in an "encoded character."
 
 Encoding Form. (See character encoding form.)
 
 Encoding Scheme. (See character encoding scheme.)
 
 Font. A collection of glyphs used for the visual depiction of character
 data. A font is often associated with a set of parameters (for example,
 size, posture, weight, and serifness), which, when set to particular
 values, generate a collection of imagable glyphs.
 
 Glyph. (1) An abstract form that represents one or more glyph images.
 (2) A synonym for glyph image. In displaying Unicode character data, one
 or more glyphs may be selected to depict a particular character. These
 glyphs are selected by a rendering engine during composition and layout
 processing. (See also character.)
 
 Glyph Image. The actual, concrete image of a glyph representation having
 been rasterized or otherwise imaged onto some display surface.
 
 ==== End of Glossary Excerpt ====
 
 Note: the glossary does not contain a definition of "character
 encoding", but it seems to be used in the Unicode context as an
 abbreviation for "character encoding form" (_not_ "character encoding
 scheme").
 
 The Java documentation is a bit confused and inconsistent in its
 terminology with respect to characters, character sets, and character
 encodings. For instance "the Java platform uses Unicode as its native
 character encoding" (i18n docs), but at the same time UTF-8 and UTF-16
 are referred to as "character encodings" that all Java implementations
 must support. Elsewhere in the docs these are the names of "charsets",
 which is to say that in some places the docs call them "encodings" and
 in others "charsets." Moreover, in Java 1.4 there is now
 java.nio.charset.Charset, "A named mapping between sequences of
 sixteen-bit Unicode characters and sequences of bytes." This is
 consistent with MIME, but different from Unicode usage (which would call
 such a thing a "character encoding scheme", except that it also implies
 a certain collection of characters to which it can apply).
 
 RFC 2045 (MIME) says, in part:
 NOTE: The term "character set" was originally to describe such
 straightforward schemes as US-ASCII and ISO-8859-1 which have a
 simple one-to-one mapping from single octets to single characters.
 Multi-octet coded character sets and switching techniques make the
 situation more complex. For example, some communities use the term
 "character encoding" for what MIME calls a "character set", while
 using the phrase "coded character set" to denote an abstract mapping
 from integers (not octets) to characters.
 That describes terminology similar to Unicode's current terminology, but
 not exactly the same.
 
 Java documentation has also changed over the years with regard to how it
 names these things.
 
 What a muddle.
 
 As this is a Java newsgroup, we are stuck with the inconsistencies of
 the Java documentation, at least to some extent. We are also stuck with
 the ambiguity of some of our terms (note, for instance, the four (four!)
 different definitions of "character" above -- I find that I personally
 use the word in each of those ways). On the other hand, there seem to
 be some points on which there is little disagreement (at least in
 official douments) such as a "font" as a collection of glyphs, a "glyph"
 as a depiction of a character, and a definite distinction between glyphs
 and characters (whatever those are).
 
 Luckilly, in a Java context there is little call for usage of the term
 "character set" in the Unicode sense, so it seems reasonable and
 appropriate that in this venue we should use it in the MIME / Java NIO
 sense (as defined by java.nio.charset.Charset.) "Charset" is a synonym.
 
 By an "encoding" or "character encoding", I think we generally mean what
 Unicode calls a "character encoding scheme" with the implicit
 recognition that in a Java context the "character encoding form" is the
 one defined by Unicode. This is closely related to a "charset" as
 defined in the previous paragraph.
 
 That leaves only "character" of the five terms of interest, and I don't
 think I can do much better than the Unicode glossary there, except to
 note the existence of class java.lang.Character, a related but distinct
 entity. A character is definitely distinct from a glyph -- the latter
 is a possible representation (or part of one) of the former, for some of
 the defintions of the former.
 
 John Bollinger
 email***@***.com
- 2
 - Project confusionOkay I'm not exactly sure what I'm supposed to do. I know I should
 create a file that creates an abstract tree but I can't figure out
 exactly what the other programs do and how I should use them to
 implement an abstract tree. So if someone could please shed some light
 as to what direction I should be going in it would be a lot of help.
 The website as to where the assignment is located is as follows:
 http://www.cs.uiowa.edu/~slonnegr/plc/. The pdf that describes the
 homework is under the link Parse Homework under the Homework header.
 Agains thanks for the help.
- 2
 - executeQuery() doesn't time out, blocks indefinitely on network failureI am developing an application that must gracefully recover from
 network failures, however I noticed that executeQuery() never returns
 or throws an exception for a time out when the network goes down (which
 I simulated by unplugging my ethernet cable). The TCP connections of
 all my pooled database connections remain open and dead even after
 plugging the cable back in. Calling queryTimeout() explicitly has no
 effect--executeQuery() stays blocked on network IO forever. Is there a
 way to time out executeQuery(), or some way to stop it from never
 returning?
 
 I'm using version 10.2.0.1.0 of Oracle's JDBC driver with the 1.5 JDK.
 
 Code:
 
 import java.util.*;
 import java.sql.*;
 import oracle.jdbc.pool.*;
 
 public class Oracle
 {
 private OracleDataSource oracleDataSource;
 
 public Oracle() throws Exception
 {
 oracleDataSource = new OracleDataSource();
 oracleDataSource.setURL("jdbc:oracle:oci:@dev");
 oracleDataSource.setUser("dbp");
 oracleDataSource.setPassword("dbp");
 oracleDataSource.setConnectionCachingEnabled(true);
 }
 
 public void validate()
 {
 Connection c = null;
 Statement s = null;
 ResultSet r = null;
 
 try
 {
 System.err.printf("connecting...\n");
 c = oracleDataSource.getConnection();
 System.err.printf("connected\n");
 s = c.createStatement();
 s.setQueryTimeout(1);
 
 for (;;) {
 System.err.printf("executing...\n");
 r = s.executeQuery("select 1 from dual");
 System.err.printf("executed\n");
 r.close();
 try { Thread.sleep(1000); } catch (Exception e)
 { }
 }
 }
 catch (Exception e)
 {
 e.printStackTrace();
 try { r.close(); } catch (Exception ee) { }
 try { s.close(); } catch (Exception ee) { }
 try { c.close(); } catch (Exception ee) { }
 }
 }
 
 public static void main(String[] args)
 {
 Oracle oracle = null;
 
 try
 {
 oracle = new Oracle();
 oracle.validate();
 }
 catch (Exception e)
 {
 e.printStackTrace();
 System.exit(1);
 }
 }
 }
 
 Output:
 > javac -cp ./ojdbc.jar Oracle.java && java -cp .:./ojdbc.jar Oracle
 connecting...
 connected
 executing...
 executed
 (ethernet cable unplugged...)
 executing...
 (i waited a very long time, and nothing happened...)
- 2
 - Socializing site EXCLUSIVELY for TECHIESTechnopax.com, (http://www.technopax.com) the first socializing web
 portal exclusively catering to the IT Professionals world over is
 launched.
 
 This web portal will be a common online platform for IT industry
 related professionals. Technopax.com primarily targets computer
 software and hardware professionals, networking & system
 administrators, nano Technologists, bio-technologists, graphics &
 animation designers, BPO/Call Center/ITES employees, telecom experts,
 employees of IT Departments of all business organizations and
 technology students etc as its members.
 
 According to the promoters, an online platform exclusively for Techies
 will improve their technical and professional skills through the
 sharing of knowledge base, methodologies and skill sets. Apart from
 building vast friends circle, this will also help them to be abreast
 with the latest developments that happen in the tech front world over.
 
 Technopax.com has many features for the members to collaborate and
 socialize. It has text/audio and video chat, online clubs, events,
 forums, classified advertisements, discussion rooms, music and video
 sharing, web profiles etc. Please verify.
- 4
 - How to download metafiles using a signed appletI want an applet which, once launched, downloads 3 metafiles (files
 that it will need later on to work properly) and proceeds into a
 processing phase only if the files have been successfully fetched.
 
 So far I do not have a solution for requesting these files and writing
 them locally.
 
 Am I following the right track with URL and HttpURLConnection, or
 should I be looking into packages like the Apache Jakarta project?
 
 Is there possibly a more straightforward way to instruct the JRE to go
 get file "http://www.foo.com/dist/localdata.dat" and put it at
 location "C:\localdata.dat" ?
 
 Is there possibly some correlation between the domain mentioned in my
 signing certificate and the domain from which I download any
 particular file?
 
 Thanks for any ideas,
 
 Brian Herbert Withun
- 5
 - odd mouselistener issueHi Guys
 
 I'm probably doing something stupid... but:
 
 I've got a JFrame with borderlayout. In the centre box, I've got a
 JPanel. If I add a mouselistener to the jframe, it works fine (but
 I've got coords relative to the frame which is correct but not what I
 want - I want coords relative to the panel). However, when I add the
 mouselistener to the panel, I get no mouseevents being returned at all.
 
 Any ideas in what way I might be being stupid?
 
 TIA
 
 Peter.
- 14
 - SinotticoDovrei sviluppare un sinottico in java qualche idea non so da dove partire
 Grazie
- 14
 - How to use an unsigned number in Java?People, is there a library that allow me to use unsigned numbers? I need
 this to implement a protocol but I don't want to have to keep masking a
 long number.
- 14
 - XMPP Java bot loop questionI want to write a bot for XMPP (Jabber) in Java (1.6) using smack
 libraries (http://www.igniterealtime.org).
 
 I have already written a GUI client using smack, so I'm familiar with
 how it works.
 
 For the bot however, I'm in doubt about the main loop in combination
 with event listeners. The bot basically just sits idly (until explicitly
 stopped) listening for presence changes of contacts. The presence
 changes are dealt with by a roster listener.
 
 How would I wait for those events and have the application keep
 executing? I am a bit clueless aobut threads in Java, but I have used
 them in Delphi...
 
 On a side note, if anyone can shed light on how to use the commons
 daemon (http://commons.apache.org/daemon/), that would be useful later
 on.
 
 Many thanks in advance,
 --
 Sabine Dinis Blochberger
 
 Op3racional
 www.op3racional.eu
- 15
 - public static final - compilation errorOn Tue, 28 Jun 2005 17:49:11 +0200, Kamil Roman wrote:
 
 > Hi,
 >
 > is it possible to initialize a public static final member of a class in
 > the class' constructor? I try to do this and I receive error message:
 >
 > variable PLUS is declared final; cannot be assigned.
 
 {... code ...]
 
 No, the static finals need to be initialized before that. Why don't you
 use a static initializer block (static { /* ... */ }), which would be
 called at class load, in which you can initialize your members.
 
 --
 You can't run away forever,
 But there's nothing wrong with getting a good head start.
 --- Jim Steinman, "Rock and Roll Dreams Come Through"
- 15
 - basic question on Java in XPHello,
 
 can someone please tell me how to ascertain what version (if any) of Java is
 installed in a WinXP platform?
 
 my friend needs some kind of Java module installed so that she can do a
 tutorial for an online registration service.
 
 any help would be appreciated.
 
 Cynthia
- 15
 - Reporting tool to be used with swingHello All,
 
 I'm looking for a report generation tool to be used in a swing project
 I'm working. The resports will involve very complex charts and graphs.
 Kindly suggest tools which will meet these requirements.
 
 Thanks and Regards
 
 Chanchal
- 15
 - efficient way to replace char in StringBufferI normally use strings. Just starting to use StringBuffer.
 How can I do the following better? (Replace <cr> and <lf>
 with <space>)
 
 String s = DynamicPanel.dynamicCmdArea.getText(0, len);
 StringBuffer ss = new StringBuffer(s);
 int j = -1;
 while ((j = ss.indexOf("\n")) != -1)
 ss.setCharAt(j, ' ');
 while ((j = ss.indexOf("\r")) != -1)
 ss.setCharAt(j, ' ');
- 15
 - TextArea and imagesHi,
 
 I am working on a chat applet, and I would like it to show an image
 next to some text received from the server. I have looked everywhere I
 can think of for a similar piece of code, but I haven't succeeded yet.
 
 I use a TextArea for inserting the text received but I don't know how
 to insert the image into the TextArea next to the text. Is there any
 way to do this?
 I also want some of the text and the image to be hyperlinked to other
 web pages for loading upon cliking. I think I have found how to do
 this, although I haven't tried it yet.
 
 Any help specially with the first question will be appreciated.
 
 Thank you
 Miguel

Author

Message

Peter Ashford

Posted: 2004-10-3 19:29:00

Top

java-programmer, arrays of generic types Eclipse tells me that arrays of generic types are not legal, e.g.: it
won't allow the following:

QuadTree<MyNodeType> [] allQuadTrees;

Anyone know why this is the case?

Tor Iver Wilhelmsen

Posted: 2004-10-3 22:53:00

Top

java-programmer >> arrays of generic types Peter Ashford <email***@***.com> writes:

> Eclipse tells me that arrays of generic types are not legal, e.g.: it
> won't allow the following:
>
> QuadTree<MyNodeType> [] allQuadTrees;

Do you use a version of Eclipse that supports JDK 1.5/5.0?

From http://www.eclipse.org/jdt/index.html:

"J2SE 1.5 support was *not* officially scheduled for Eclipse 3.0
release, since J2SE 1.5 was not finalized before 3.0 release date,
and we did not want to jeopardize the 3.0 release by integrating
beta quality tooling. In parallel to the 3.0 effort, we were still
implementing an experimental version of JDT Core with 1.5 support
(mostly focusing on adding generics support to Eclipse Java
compiler). You may find details and previews of our ongoing effort
(codename "Cheetah") in our update area."

However, it seems this "experimental" support has been improved in
3.0.1 which is the latest public release.

IchBin

Posted: 2004-10-4 9:35:00

Top

java-programmer >> arrays of generic types Peter Ashford wrote:
> Eclipse tells me that arrays of generic types are not legal, e.g.: it
> won't allow the following:
>
> QuadTree<MyNodeType> [] allQuadTrees;
>
> Anyone know why this is the case?
Depends on what version of eclipse you are running. Also they do not
have full JDK 1.5 support yet.

Better to Post to Eclipse newsgroup: news.eclipse.org's eclipse.platform

--

Thanks in Advance...
IchBin
__________________________________________________________________________

'Laughter is inner jogging'
- Norman Cousins, editor and author (1915-1990)

Peter Ashford

Posted: 2004-10-6 17:07:00

Top

java-programmer >> arrays of generic types Tor Iver Wilhelmsen wrote:
> Peter Ashford <email***@***.com> writes:
>
>
>>Eclipse tells me that arrays of generic types are not legal, e.g.: it
>>won't allow the following:
>>
>>QuadTree<MyNodeType> [] allQuadTrees;
>
>
> Do you use a version of Eclipse that supports JDK 1.5/5.0?
>
> From http://www.eclipse.org/jdt/index.html:
>
> "J2SE 1.5 support was *not* officially scheduled for Eclipse 3.0
> release, since J2SE 1.5 was not finalized before 3.0 release date,
> and we did not want to jeopardize the 3.0 release by integrating
> beta quality tooling. In parallel to the 3.0 effort, we were still
> implementing an experimental version of JDT Core with 1.5 support
> (mostly focusing on adding generics support to Eclipse Java
> compiler). You may find details and previews of our ongoing effort
> (codename "Cheetah") in our update area."
>
> However, it seems this "experimental" support has been improved in
> 3.0.1 which is the latest public release.

I'm using the cheetah plugin which provides generics support. Eclipse
is not complaining about the use of generics - my code is littered with
it - it is complaing just about arrays of generic types.

Index ‹ java-programmer

Next
- 1
 - Making a soundcard objectI have this idea of making a modem, that requires the soundcard to act
 as my A/D and D/A, and in the middle will be my attempts at DSP. I
 came up with this object, and it seems to test OK, but I could use
 some constructive criticism, as I am definately at the OO 101 stage.
 
 Merry Christmas, and a Happy New Years soon!
 
 /**
 * SoundCard.java
 *
 * @version 1.0, 1 December 2007
 * @author Steve Sampson, K5OKC
 *
 * Public Domain (p) December 2007
 */
 
 package modem;
 
 import javax.sound.sampled.*;
 import java.io.*;
 
 public class SoundCard {
 private static AudioFormat format;
 private static TargetDataLine targetLine;
 private static SourceDataLine sourceLine;
 private static AudioInputStream sound;
 
 public void SoundCard() {
 }
 
 /*
 * Initialize Sound Card
 */
 
 public boolean initPCM(double dblSampleRate) {
 
 /*
 * Encoding,
 * Sample Rate (float),
 * Sample Size (In Bits),
 * Channels,
 * Frame Size,
 * Frame Rate (float),
 * BigEndian (Boolean)
 */
 
 format = new AudioFormat(AudioFormat.Encoding.PCM_SIGNED,
 (float)dblSampleRate,
 16,
 1,
 2,
 (float)dblSampleRate,
 false);
 
 DataLine.Info targetInfo = new
 DataLine.Info(TargetDataLine.class, format);
 DataLine.Info sourceInfo = new
 DataLine.Info(SourceDataLine.class, format);
 
 try {
 /*
 * A source data line is written to
 */
 
 sourceLine =
 (SourceDataLine)AudioSystem.getLine(sourceInfo);
 sourceLine.open(format); // Typical buffer size is same
 as samplerate in bytes
 sourceLine.start();
 
 /*
 * A target data line is read from
 */
 
 targetLine =
 (TargetDataLine)AudioSystem.getLine(targetInfo);
 targetLine.open(format); // Typical buffer size is same
 as samplerate in bytes
 targetLine.start();
 }
 catch (LineUnavailableException e1) {
 return false;
 }
 catch (SecurityException e2) {
 return false;
 }
 catch (IllegalArgumentException e3) {
 return false;
 }
 catch (IllegalStateException e4) {
 return false;
 }
 
 if(!AudioSystem.isLineSupported(targetInfo)) {
 return false;
 }
 
 sound = new AudioInputStream(targetLine);
 
 return true;
 }
 
 /*
 * Stop, flush, and close the soundcard interface
 */
 
 public void closePCM() {
 sourceLine.stop();
 targetLine.stop();
 
 sourceLine.flush();
 targetLine.flush();
 
 try {
 sourceLine.close();
 targetLine.close();
 }
 catch (SecurityException e)
 {
 }
 }
 
 /*
 * Provide a block of Signed 16 bit PCM sound data
 */
 
 public int getPCM(int[] intSampleArray) {
 int intBytesRead;
 byte[] byteData = new byte[intSampleArray.length * 2]; //
 Convert count to bytes
 
 /*
 * Read bytes into array. This call will block if there aren't
 * enough requested bytes.
 */
 
 try {
 intBytesRead = sound.read(byteData, 0, byteData.length);
 } catch(IOException e) {
 return -1;
 }
 
 /*
 * This is designed for Little-Endian Intel machines
 */
 
 for (int i = 0, j = 0; i < intBytesRead; i += 2, j++)
 intSampleArray[j] = (byteData[i + 1] << 8) + byteData[i];
 
 return intBytesRead / 2; // convert count to words
 }
 }
- 2
 - Send ARPHello everyone,
 
 I want to verify if an IP is in my local net or not.
 If I send an ARP request and get a MAC from that then the IP is in the
 local net.
 That's why I need to send an ARP request in Java under Windows XP and
 NT.
 
 Can anyone tell my how this is done?
 Doing this native with the Windows iphlpapi.dll seems to be a bit
 complex.
 Any ideas for any easy way?
 
 Thanks.
 
 bye bembi
- 3
 - Help sought trying to add java to mozilla 1.5
 I've downloaded and gotten mozilla 1.5 to work on my desktop machine.
 However, when I visit Java enabled sites, I get a popup that tells
 me I am missing the plugin for the java-vm applet type. When I say
 "download it", the only links are for windows and linux, and I'm
 not using either of these.
 
 In the java 1.4.2_01 directory I have on my machine is a rje/plugin/sparc/ns610
 directory in which there is a .so file. But I don't see any instructions
 on what all I need to connect things together.
 
 When I try to copy that .so file into my $HOME/.mozilla/plugins directory,
 mozilla 1.5 crashes attempting to access the java applets. If I
 remove the .so, then I get a popup telling me I need a plugin.
 
 Can anyone provide additional ideas on what might be missing?
 --
 <URL: http://wiki.tcl.tk/ > In God we trust.
 Even if explicitly stated to the contrary, nothing in this posting
 should be construed as representing my employer's opinions.
 <URL: mailto:email***@***.com > <URL: http://www.purl.org/NET/lvirden/ >
- 4
 - Can I restrict permissions at runtime?I have an editor application that I've writen that needs to read and
 write XML files to disk. I'd like to extend this program by allowing
 users to extend my editor by plugging in custom code they compile using
 certain interfaces. My editor will call their code to gain use of
 their functions.
 
 However, this plugin code is untrusted, and I don't want it to access
 the filesystem or network. Is there some way I can create a sandbox
 within my program in which I can run this custom code and be sure that
 it cannot do things like write to the filesystem? Perhaps create a
 separate thread with special restricted permissions?
 
 Mark McKay
- 5
 - Help with JavaPOS pleaseHi there,
 I have made an application that uses a POS printer device to print out a
 receipt,
 but there are genereal problems printing out .....
 sometimes it prints out sometimes it doesn't (??) this is not the most major
 of the
 problems. The most major problem has to do with setting the style and the
 layout of the printing.
 
 After I have opened my device, claimed it everything should be ready or ??
 I have checked to see what the method getFontTypefaceList()); returns
 and my guess was that these numbers return different numbers that are
 representatives for character sets eg fonts!!!! So I take one of these
 numbers to try it out, put a number inside the method setCharacterSet(850);
 yes .. 850 for instamce ... then I restart my application to see if the
 output
 is different, but it is not. I wonder why.
 
 and yes I have tried several other methods in the POSprinter class and
 by means of the POSprinterConst class too.
 
 Does anyone have any experience with this or am I left to keep
 experimenting?
 
 I also need to find out how to set Linebreaking, linedistancing etc etc bold
 italic and so on.
 
 Regards
 Carl
- 6
 - Toward more efficient ArrayListsRoedy Green (email***@***.com) wrote:
 : IIRC Arraylists are about 10 times slower than plain arrays. This is
 : quite a penalty to pay for not knowing ahead of time how many items
 : you will have.
 
 Can you give a pointer to a benchmark that shows this?
 Or can you build a benchmark that shows this?
 
 Can you give proof that this really is your hot spot? Most guesses
 about what to optimize is wrong.
 
 Anyway I find it hard to believe that arraylist is 10 times slower
 since the methods (get and set) does something like
 { RangeCheck(index); return elementData[index]; }.
 Ok the range check is unneccasry, it will be checked by the jvm also.
 If you use add a lot then it will check the size of the array and
 expand if neccessary. If you know in advance how many objects you will
 store this should not be a problem (you do create the list with the
 size), if you dont know in advance it will be hard to write something
 that is a magnitude faster...
 
 /robo
- 7
 - ArrayList
 Why this doesn't work:
 
 ArrayList l = new ArrayList();
 l.add(new String("aaa")));
 String[] s = l.toArray();
 
 JavaClassCast exception I got. What should I do?
- 8
 - Arrays - component type vs Element typeCan anyone explain to me the difference between an element type and a
 component type?
 
 In the java literature, arrays are said to have component types, whereas
 collections from the Collections Framework are said to have an element
 type.
 
 http://java.sun.com/docs/books/jls/second_edition/html/arrays.doc.html
 
 states:
 
 > The *component type* of an array may itself be an array type. The components of
 > such an array may contain references to subarrays. If, starting from any
 > array type, one considers its component type, and then (if that is also an
 > array type) the component type of that type, and so on, eventually one must
 > reach a component type that is not an array type; this is called the *element
 > type* of the original array, and the components at this level of the data
 > structure are called the elements of the original array.
 
 Reading that - I thought I'd 'got' the difference, but then in 10.1 (a
 para later) the terms seem to used synonomously!
 
 > An array type is written as the name of an *element type* followed by some
 > number of empty pairs of square brackets []. The number of bracket pairs
 > indicates the depth of array nesting. An array's length is not part of its
 > type.
 > The element type of an array may be any type, whether primitive or reference.
 > In particular:
 >
 > € Arrays with an interface type as the *component type* are allowed. The
 > elements of such an array may have as their value a null reference or
 > instances of any type that implements the interface.
 > € Arrays with an abstract class type as the *component type* are allowed.
 > The elements of such an array may have as their value a null reference or
 > instances of any subclass of the abstract class that is not itself
 > abstract.
 
 When describing collections from the Collections framework there is
 never any of this ambiguity/distinction - it is always "element type",
 even when talking about a collection whose elements are themselves
 collections.
 
 Am I missing a "big idea"?
 
 Any thoughts greatly appreciated.
 
 Rob
 
 email***@***.com
- 9
 - Beans with JSFI'm pretty new to programming with JSF and beans, and have been
 reading up the documentation in the book "Core JavaServer Faces"
 by D.Geary and C. Horstmann as well as online, and managed to
 get some simple programs to run, so at least I now understand
 some of the basics.
 
 However, I've got quite a lot of existing code in HTML and
 JavaScript that works, although not fully cleaned up yet, and I want
 to make as few changes as possible in order to modify it for using
 beans with JSF. Specifically, some months ago I wrote some
 client-side code which is backed up online at
 http://csharp.com/simulator/simulator.html, which I'm in the process
 of modifying for JSF. The links at the bottom take you to
 .../option1.html and .../option2.html, with the original source code
 at
 respectively .../option1.txt and .../option2.txt. At the moment the
 code is not linked to code on a server, so only the JavaScript works
 with the forms.
 
 The index page didn't need much work, with the main change being
 to include the JSF tags at the top (I'm leaving work on the counter
 until later). The option1 page is mostly one large form, and what I
 have since done is to keep the form as it is, except that it only
 operates with JavaScript, with the post, action, and JavaScript
 function calls at the beginning removed, together with the "Submit"
 and "Reset" buttons at the end. I put these two buttons together
 with calls to the JavaScript in a JSF form immediately below the
 end of original form, and after making a few changes to the
 JavaScript, got the JavaScript to work correctly and validate the
 form.
 
 My question is how do I send to the server the contents of the
 original form, including the hidden fields? Do I have to create a
 hidden field in the JSF form for each value entered in the main form,
 and create a bean for each of these values, or is there some way
 of sending the whole contents of the form to a bean, which can then
 parse the values. I want to avoid turning the original form into a
 JSF form, as it would probably mean making many changes to the
 JavaScript, which would require extra work and debugging.
 
 Exactly the same will be done with the option2 page once option1
 has been sorted out, and I would be most grateful for some advice.
 
 Christopher Sharp
- 10
 - History of objects?Hi
 
 a relatively complex project I am working on now has a need for
 "versioning". I mean, we have a system for administration of data (creating
 and updating) in a database, and this data needs to be saved as separate
 versions each time it is updated - a lot like a CVS.
 
 The data is in the main "bridges", which have lots of data (name, location,
 height etc), and lots of related data: persons (controller, supervisor);
 tasks to be performed...
 
 It should for example be possible for a user to view a "bridge" as it looked
 on a certain date in the past, with all its related data (as they also were
 at that date).
 
 Does anyone have some good ideas about how we can save a history of versions
 of all our objects? Where can I start to look for good ideas? Could we use
 CVS via some sort of java api?
 
 Thanks,
 Peter
- 11
 - want to sort tables inside a complex mechanism, what can be the approach?I have a situation where first we are fecthing some ids(list of say
 version ids using hibernate form database)
 then keeping those list of data in a Pager Object(Paging mechanism
 displays 100 rows per page out of complete sa 100 or so.)
 This pager class does two things one takes whole list of ids
 (Collection of version_id).
 (Every time based on search criteria it changes. For searching in
 hibernate values are hardcoded. Want modification with minimal changes
 as many things are interrelated here.)
 and other thing it checks no. of contents based on that displays data
 per page(100 here).
 It means stores all data from database and send it oage by page.(First
 thing to notice)
 
 Next all this is getting stored in Report page where it searches other
 column names based on ids(version_id) the other column names are
 getting changed for different requests so what we do is take all other
 columns collectAllExtraFields(this is also getting changed everytime
 based on what is getting searched.)
 Now all this is getting accumulated while displaying but as we know
 what to display we hardcoded all fields required to display based on
 search. But all fields are searched based on the id fetched from
 database first time which Pages is storing.
 like this
 
 Search for product user information & retrun results in the form of a
 paged table for components used by specific product
 
 ComponentVersion versionObj =
 versionHandler.getComponentVersion(versionId);
 String CAUsers = ctHelp.getCAUsersSection(versionId);
 tableBody = tableBody + ((i%2 == 0) ? "<tr
 class='table_banded_row' valign='top'>" : "<tr class='table_row'
 valign='top'>");
 tableBody = tableBody + "<td class='table_data'>" +
 procHelper.getCompVersionLink(versionId,
 versionObj.getCompName(), versionObj.getCompVersion()) + "</td>";
 tableBody = tableBody + "<td class='table_data'>" +
 CAUsers + "</td>";
 tableBody = tableBody + "<td class='table_data'>" +
 versionObj.getComponent().getType() + "</td>";
 tableBody = tableBody + "<td class='table_data'>" +
 versionObj.getComponent().getVendor() + "</td>";
 tableBody = tableBody + "<td class='table_data'>" +
 versionObj.getRecommendationType() + "</td>";
 tableBody = tableBody + "</tr>";
 
 /** Get ComponentVersion ID with hyperlink to ComponentVersion Detail
 page
 */
 public String getCompVersionLink(long versionId, String compName,
 String compVersion){
 return "<a class='datalink' title='" +
 this.getComponentFlyOverText(versionId) + "'
 href='/techstacks-v2_1/content/components/componentDetail.jsp?versionId="
 + versionId + "'>" + compName + " " + compVersion + "</a>";
 }
 
 this is getting called by Report.jsp to display.
 As this is getting changed everytime its called form classes not used
 in jsp directly i think.
 
 Now original objective is to sort all these displayed columns.
 If user clicks on any of the column name everything sholud get sorted
 on that basis.but sholud not call databse for same again by using same
 id and mapping with any new column name this sholud be done. Paging
 mechinasm to be used as it is if possible without major changes.
 
 i don't know where to start with as started looking on this code just
 2-3 days back only.
 
 Vj
- 12
 - writing java daemon server: start and stopDear everyone,
 
 I am trying to write a server program to do some monitoring.
 I am using Windows 2000 platform.
 I've seen that there is some server program can start server by
 specifying command like "server start" and stop it like "server stop".
 
 I am wondering how to do it in java language since java is running in
 the JVM.
 1. Is it prossible to send signal to kill the process just like c lang
 ?
 2. Do java have process ?
 3. How about if java thread can be killed by those deprecated method
 like thread.stop(), can I find the current running thread and stop it
 ?
 4. Any suggested method to do the server stop which can stop the
 current running java program in JVM ?
 
 Thank you for helping
 Calvin
- 13
 - I would like to open a frame with in a frame.I would like to open a frame with in a frame. I do not want to have seperate
 class. Rather I would like to have one class with two frames. A little like
 visual basic does.
- 14
 - What will be your DAO design ?For the following tables, which is a general rdbms design, what classes will
 you create for accessing these tables ?
 
 Table 1 : Group
 group_id (PK)
 group_desc
 
 Table 2 : User
 user_id (PK)
 user_name
 
 Table 3 : Group_User
 group_id (FK)
 user_id (FK)
- 15
 - 9?. Steps To Improve Your FlyingThere are many things that you can do when you fly to make yourself a
 safer and better pilot. Too many pilots get careless and stop doing
 fundamental things that could save their lives. Here are some simple
 things that you can do to improve your flying.
 
 1. Use your rudder pedals.
 
 It seems simple, right? Well, too many people neglect to get in the
 good habit of using them. Use them during taxi, takeoff, climbs,
 cruise, maneuvers, descents, and landing. Get the picture - Use them
 all the time.
 
 You can know exactly how much to use them during flight by looking at
 the slip/skid indicator. That is the ball of the turn coordinator. As
 long as the ball is centered between the lines, you are using the
 right amount of rudder. If the ball is outside the lines, add rudder
 in the direction that the ball is located.
 
 For instance, if the ball is to the right, add right rudder. An easy
 way to remember this is to "Step on the ball." Add enough pressure to
 re-center the ball.
 
 There are a lot of things happening when you are airborne. Correctly
 using your rudder will make you a better pilot, keep your passengers
 happy, and show your piloting professionalism (something you need to
 have, even if you are not a professional pilot). Remember, step on the
 ball.
 
 2. Use Your Checklist
 
 As you are flying, make sure that you use your checklist for each
 portion of the flight. There are checklists for everything from
 preflight to securing the airplane. Most airplanes have a checklist in
 the owner's manual that you can use during your flights. Also, when
 you learn to fly most flight schools have checklists that are
 available for their students.
 
 But checklists aren't put there to look pretty. Your job is to use
 them. If you get in the habit of using one each flight, you will be
 that much safer. It's not going to do you any good in your flight bag.
 Even if you know the items by heart, still double check yourself
 anyway.
 
 Another thing, if you need to add something personal to your checklist
 (like don't forget your sunglasses, or turn off your cell phone so the
 battery won't run down as it searches for a signal in flight) do this
 as well. As long as you have all the required items included, add any
 that will help you personally during your flight.
 
 3. G.U.M.P.S.
 
 Whether you use G.U.M.P.S. as your landing checklist or not, get in
 the habit of using a memorized checklist for your return to earth. In
 a complex airplane, Gumps is; Gas, Undercarriage, Mixture, Propeller,
 and Seatbelts. In a non-complex airplane, Gumps could be; Gas,
 Undercarriage, Mixture, Power, and Seatbelts. Of course you don't
 actually have to lower your gear on a fixed gear plane, but it is best
 to remind yourself anyway. That way, when you do transfer to a
 retractable gear airplane, you won't have to add anything to your
 checklist. This also happens to be one of the most important checklist
 items of the whole flight. So you will already be in the habit of
 checking your landing gear when you get to the point where it really
 matters.
 
 4. Weight and Balance
 
 Never ever forget to precisely calculate your weight and balance for
 each flight. Too many people have gotten lazy and careless, and have
 added extra weight in the form of passengers or cargo to their
 airplanes, thinking that everything is ok. Isn't there room for error
 - a little safety cushion, if you will - in the maximum useful load?
 Why would you even want to know? If you take this attitude with your
 flying, you are putting yourself and your passengers in a very
 dangerous situation. Never operate out of the manufacturer's set
 limitations for your airplane. They are there for a reason; to keep
 you safe!
 
 5. T.O.L.D.
 
 Takeoff and Landing Data should be calculated for every flight as
 well. Make sure that you are very familiar with all of the runways of
 intended use and their lengths and widths. If it is not something that
 you or your airplane can handle, don't make the flight. Don't get in
 the habit of assuming that just because you are in a Cessna 172 that
 every landing strip is suitable for your flight. Calculate your
 takeoff and landing distances for each flight, taking into
 consideration the density altitude and aircraft performance.
 
 6. Appropriate Radio Calls
 
 One flying safety item that can easily be performed is making sure
 that you make your radio calls at the appropriate time. Whether you
 are flying out of a towered or uncontrolled airport, be professional
 with your radio calls. One common error is made at uncontrolled
 airports, when after an airplane lands, the pilot calls clear of the
 runway while part or all of the airplane is on the runway side of the
 hold short line. This is dangerous! What if your airplane malfunctions
 and you are stuck on the runway and another airplane thinks it's safe
 to land? This is a hazardous situation that can easily be avoided. At
 non-towered airports, it's better to not make any radio call at all,
 than to make a dangerous one. Get it right!
 
 7. Complete Runup
 
 You have done a complete preflight inspection and are now ready to
 takeoff. Make sure you do a complete engine runup as well. Check every
 aircraft system while you are still on the ground before you get in
 the air. Determine that all of your radios, comm and nav are
 functioning. Check your vacuum and electric gyros. Check your flight
 controls and your engine gauges. Know that when you take off, you are
 as safe as you can be. There is no reason to rush through your runup.
 
 8. Situational Awareness
 
 Situational awareness is when you know exactly what is happening with
 your flight and with what is going on around you. On the ground, you
 need to make sure that you are aware of other airplanes that are
 taxiing and using the runway. In the air, use the radio and your eyes
 to know exactly where other airplanes are in relation to you as well
 as their intentions. But situational awareness is not just limited to
 knowing where other airplanes are. You also need to know exactly what
 is happening with your airplane, the weather, airspace, the winds,
 your location, what you would do in an emergency, etc. Regardless of
 whether you are flying cross country or local, for fun or for
 training, don't assume everything is alright. Know what is happening
 around you.
 
 9. Fly the plane from engine start to shutdown
 
 When it comes to flying, make sure that you are maintaining vigilance
 at all times in the airplane. Too many times pilots zone out at some
 point in the flight. For many pilots, that time is before takeoff and
 after landing. Make sure that even when you are on the ground, you are
 flying the airplane. Keep a watchful eye out for other aircraft and
 don't rely on the tower to separate ground traffic. Position your
 flight controls so that you have the proper crosswind correction,
 regardless of the wind speed. Even if the wind is calm, look at the
 wind sock and taxi as if the wind is really blowing in the direction
 indicated by the sock. Although you are on the ground, your control
 surfaces are still somewhat effective. Treat them as if your safety
 depends on their position.
 
 9?. Have Fun
 
 Even though it sounds simple, keep your flying fun. When you are in
 the air, you are living a dream. Don't forget it!
 
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