Get Some
General => Technology & Hardware => Topic started by: Tiwaking! on March 28, 2010, 08:05:57 pm
-
This thread is where you can find or post useful Java information, code snippets, tips or tricks.
I'll start with an amazingly useful tool:
Stephen G Wares (http://stephengware.com/) incredible Sound to Class tool (http://stephengware.com/projects/#stc) which turns a sound file to an independent, thread based .java file!
You should also check out the Image to Class file which is just below the previous link
My own contributions to this thread are:
Working with JApplets: Your guide to frustration ville
Applets and JApplets are horrible. They hate you. They laugh at your efforts to tame them and it just isnt worth bothering to use them
HOWEVER: If you are stubborn like me, and want a quick, easily distributed, NON-INTRUSIVE, SECURE and platform-independent method of getting your program out and about then they are a Godsend. A God which hates you and considers your efforts to spread your program to be pitiful at best, but a godsend nonetheless.
For starters: If you need file WRITE access, forget it
You will need to use CGI scripts to do so. If the server hosting your Applet has disabled cgi, forget it.
If you need file READ access, prepare for pain
Despite everything you read on the internets, you CAN initialise a FILE() object. HOWEVER:
You cannot read it and
You cannot write to it
This is akin to buying a dirty magazine and finding there is no cover art and the pages are solidly stuck together with some unidentifiable substance. It is about as disappointing too
What you need to do is to CHANGE your STRING file/folder path name into an INPUTSTREAM object BASED on the pathname. This is done as follows (spoilered to prevent cluttered thread):
BufferedInputStream inputStream = new BufferedInputStream(
this.getClass().getResourceAsStream(path));
Note that the getResourceAsStream() method returns a BufferedInputStream type
Now here is the fun bit: If you need a STRING from the file (like a filename or foldername)
public void convertStreamToString(InputStream is,String path){
if (is != null) {
StringBuilder sb = new StringBuilder();
String line;
ArrayListarray=new ArrayList();
try{
BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
while ((line = reader.readLine()) != null) {
sb.append(line).append("\n");
}//while line=reader.ReadLine
is.close();
}catch(IOException in){
System.err.println(in.toString(),"Error in Convert Stream To String!");
}//catch
}//if is != null
System.out.print(sb.toString());
}//method
Simple? Well. Not really. If you need to get a list of all the FILES in a directory....well. That can be a story for another day
You can also retrieve IMAGES via the InputStream method as well
private ImageIcon loadImage(String path) {
int MAX_IMAGE_SIZE = 240000; //Change this to the size of
//your biggest image, in bytes.
int count=0;
BufferedInputStream imgStream = new BufferedInputStream(
this.getClass().getResourceAsStream(path));
if (imgStream != null) {
byte buf[] = new byte[MAX_IMAGE_SIZE];
try {
count = imgStream.read(buf);
imgStream.close();
} catch (java.io.IOException ioe) {
System.err.println("Couldn't read stream from file: " + path);
return null;
}
if (count <= 0) {
System.err.println("Empty file: " + path);
return null;
}
return new ImageIcon(Toolkit.getDefaultToolkit().createImage(buf));
} else {
System.err.println("Couldn't find file: " + path);
return null;
}//clse
}//method
In summation: Never forget that nextInt() will leave an empty string behind!
Edit: Edited with code tags and proper formatting
-
If you're not being paid lots of monies then you're being wasted
that syntax hurts my brain let alone trying to comprehend it
-
If you're not being paid lots of monies then you're being wasted
I'd point you in the direction of Bell. He's the man when it comes to Java.
Its been forever since a bedroom programmer led the way in the development of anything great
that syntax hurts my brain let alone trying to comprehend it
Compared to the old procedural languages, Java is incredibly easy to learn. Almost too easy, which is a problem to people who are familiar with C and C++ but not C# (which is basically Java)
The only thing you really need is a compiler. If you dont like command line compiling then you can use the easy to use program I use, BlueJ!
http://www.bluej.org/download/download.html
There is an exceptionally powerful and useful tool called Eclipse as well. I dont use Eclipse at home and begrudgingly use it in class since it is the only way to do Android/Nexus One development programs easily
http://www.eclipse.org/downloads/
I would not advise using this unless you are very familiar with Object Orientated Programming and Java.
A simple Java program: Printing a line of text
public class HelloCodex{
//beginning class bracey
public static void main(String[]args){
//this bracey denotes the beginning of a method. All braceys need a beginning bracey and an end bracey
System.out.println("Hello Codex! We must meet in TF2 one day");
//Note that all lines processable code must end with a semi-colon (;) Lines
//Thusly you could have a single line of code which spans multiple 'lines' but terminates with semi-colon
}
//main method, the 'executable' you could say
}
//class <- note that the // denotes a comment. This will not be processed
-
i heard xeno was pr0 at java..
-
If you're not being paid lots of monies then you're being wasted
that syntax hurts my brain let alone trying to comprehend it
The Java / C# Syntax is nice, but it looks much nicer when it's formatted and highlighted.
It would be good to have some kind of code highlighting for the forums, for the two people who post code.
public static List<Tag> GetCards(int loginID, int groupID)
{
Timereg tDx = GetConnection();
int userID = CheckForValidLoginSession(loginID);
//Retrive list of staff
var Results = from c in tDx.CardTag
where c.GroupID == groupID
select c;
List<Tag> siteList = new List<Tag>();
foreach (CardTag cTag in Results)
{
Tag nSite = new Tag(cTag);
siteList.Add(nSite);
}
return siteList;
}
-
Tiwa, please please please use the [noparse]
If you're posting php, syntax highlighting (shit though it is) is supported through the [php] tag.
Syntax is similar, so you could see how you get on using it for java. It'll probably be fine (especially since the highlighting is quite poor, as I mentioned).
-
Tiwa, please please please use the [noparse]
Ahh I didnt even know the CODE tag existed!
The evils of the Scanner
I discovered something very interesting today: Do not use the java.util.Scanner in your programs!
When used on Android phones it slows down to a crawl. We are talking 1 - 3 minute boot up times for text files which have 150 lines in them
The exceptionally boring and unhelpful description of the Scanner is found here (http://64.233.169.104/search?q=cache:EQ6ZWMc9yGgJ:www.ebenhewitt.com/presentations/New_Features_in_Java_5.ppt+java.util.Scanner+performance+issue&hl=en&ct=clnk&cd=20&gl=us)
However in the real world, the scanner acts like this (http://osdir.com/ml/Android-Beginners/2010-03/msg00419.html)
Hi guys,
I want to use Scanner class to read a list of floats from a text file
It seems however that this is incredibly slow (it took 30 minutes to
read 10,000 floats)
This appears to be the reason why my JApplets run/load incredibly slowly too. They have been fixed now
What you SHOULD use instead
Warp back ten years to 2000 and use the old way of splitting strings:
String line = "This Line Is Split Using Spaces";
String[]newLine=line.split(" ");
This splits up the line using SPACE as the delimiter and creates and Array of Strings. In this case it would look like:
newLine[0] is "This"
newLine[1] is "Line"
newLine[2] is "Is"
etc
To read a line from a file without using the scanner you will need to use the BufferedReader object as follows:
BufferedReader br=new BufferedReader(new FileReader("yourFile.txt"));
String line;
while((line=br.readLine())!=null){
System.out.println(line);
}
In conclusion: java.util.Scanner is NOT your friend. Avoid it
-
I didn't even know scanner existed, I've always just used input streams and readers.
-
I'd point you in the direction of Bell. He's the man when it comes to Java.
I've only done a paper or 2 in java 4-5 years ago, I'm pretty much a noob.
I always tried to do C++ while I was studying, even tho Ken kept pushing me to do java heh.
Oh and I hope you liked my little Q and A time at SIT heh.
Ken always drags me into the classroom everytime I go to say hi.
-
Oh and I hope you liked my little Q and A time at SIT heh.
Ken always drags me into the classroom everytime I go to say hi.
Ken didnt even warn us you were coming AND you guys came on the worst day:
The last class of the last day of school and the second least liked class (First being SAAD with Phillip Chan)
Next time you are down, I will show you the 2d fighting game I have made into which I have animated myself. It should be fully ready (two characters, full sounds, full animations) in a week and then a week of testing. Hell if I am really on the ball, I might be able to convert it into a JApplet and stick it on my website. I havent figured out how to use a KeyListener on a JApplet yet. The Applet loses focus to the webpage it is on so never allows key input
ANYWAY, on topic:
Reading a Directory: The Java Way!
Reading a directory is ridiculously simple in Java. Make a File which is the name of the directory, then getFiles()
File directory=new File("c:\program files\Java");
String[]files=directory.getFiles()
This will list everything in the directory. Want to know if what you have got isFile() or isDirectory()? Simply use those two methods which will return TRUE if they are a FILE or a DIRECTORY
You can utilise this technique any time you need to make a list of files or objects during runtime. By listing everything in a directory holding all your CLASS files, you can make an array of Objects which exist inside a directory
Enjoy!
-
The only thing you really need is a compiler. If you dont like command line compiling then you can use the easy to use program I use, BlueJ!
[url]http://www.bluej.org/download/download.html[/url]
There is an exceptionally powerful and useful tool called Eclipse as well. I dont use Eclipse at home and begrudgingly use it in class since it is the only way to do Android/Nexus One development programs easily
[url]http://www.eclipse.org/downloads/[/url]
I would not advise using this unless you are very familiar with Object Orientated Programming and Java.
BlueJ is only easy because it does things for you that you should be doing yourself to really understand how it all works.
Eclipse is the man, so extensible as well. I even use it for PHP development, yus!!
-
I used Eclipse for my Java programming, it was pretty good.
-
Fun fact: The name 'Eclipse' is a dig at Sun
-
Previously on Tiwaking! gives you bad advice...
This appears to be the reason why my JApplets run/load incredibly slowly too. They have been fixed now
What you SHOULD use instead
Warp back ten years to 2000 and use the old way of splitting strings:
String line = "This Line Is Split Using Spaces";
String[]newLine=line.split(" ");
This splits up the line using SPACE as the delimiter and creates and Array of Strings. In this case it would look like:
newLine[0] is "This"
newLine[1] is "Line"
newLine[2] is "Is"
etc
Well it turns out this is horrifically wrong.
the split() command is INCREDIBLY slow in an emulation or android environment. Apparently it searches the line multiple time for the markers which is fine for our desktops, but for limited environments: Bad news.
Replace all uses of split("STRING","REPLACEMENT_STRING") with a loop which iterates, for example:
[s]line.split("/","")[/s]with
newLine=line.substring(line.indexOf("/"));And use an interator
-
was going to post some shit here, but i think i deleted all my java projects...
had some neat stuff like recursively traversing the the contents of a folder and its subfolders and building a balanced binary tree from the contents to do some quick searches
-
This post is a warning to anyone attempting serialization in Java and does not contain code. Actual code will appear at a later date
Serialization and Java
Serialisation is the 'streaming' of objects, squishing them into a transmittable/compact form.
After 18 hours of programming I managed to master the art of this horrible, horrible concept. There are FOUR VERY BAD THINGS you have to learn endure.
Warning one
You MUST declare the ObjectOutputStream BEFORE otherwise your entire program will deadlock with no errors and no warning.
Warning two
You MUST flush the ObjectOutputStream before doing ANYTHING else.
Warning three
You MUST flush the ObjectOutputStream ALWAYS after sending an object.
Warning four
This one took me four hours to figure out.
You CANNOT make a Data Member('Global Variable' to you non-Javaese) of a Serializable class.
You can disagree with me about this last warning, but I promise you: I will laugh at you constantly when you repeatedly fail, ESPECIALLY when it takes less than six characters to completely corrupt your program.
Conclusion
There are two other things you have to do before serialization can occur.
1. The class you wish to serialize must implement java.io.Serializable.
1 a) Warning: Serialized classes cannot recursively call one another or be dependent on another class. Well, they can. But unless you've mastered the fiddly bastards then I wouldnt advise attempting it.
2. ObjectOutputStream and ObjectInputStream are required for the passing of Objects out and in. ObjectInputStream.readObject() is a blocking call which will not execute until it recieves input.
2 a) These two streams will completely hog the resources available from a Socket. You cant send objects and text chat along the same stream (unless someone knows of a way you can).
Please be warned and be program safe!
-
Serialization a great way to pass things around.
Just have to remember that it essentially needs to compress EVERY object that is associated with the one you're trying to save/send.
Everything must be nice, not just whatever implements Serializable.
-
In the tradition of discovering incredibly weird or obscure errors:
JTabbedPane dangers
It took an hour before I fixed it (a simple try/catch) but I managed to generate an impossible error today.
What is the difference between this:
public class ClientTabbedPane extends JTabbedPane{
public void add(ClientTextPanel panel){
add("I am a panel",panel);
}
}And this:
public class ClientTabbedPane extends JTabbedPane{
public void add(ClientDisplayPanel panel){
add("I am a panel",panel);
}
}
Answer?
If you said "One is a ClientDisplayPanel and one is a ClientTextPanel" then you get half a mark.
The real answer is:
Code snippet two throws an impossible to throw error!
Notably THIS error:
java.lang.ArrayIndexOutOfBoundsException: -1
This error is impossible to throw. The reason a JTabbedPane would throw this error is if you:
1. Try to remove a component from index -1
2. Select a tab which is at index -1, which is an impossibility because tab -1 is the index of a non-existent tab.
Note that I have ADDED a component, not removed one.
the fix is:
public class ClientTabbedPane extends JTabbedPane{
public void add(ClientDisplayPanel panel){
try{
add("I am a panel",panel);
}catch(Exception ignoreStupidError){}
}
}The panel is added. The impossible error is thrown. Program continues.
Cripes Java can be screen-punchingly frustrating sometimes.
Edit: Wow.
The program goes, but sometimes if the tab creation is a wee bit too slow it throws a 'non-existent tab' error.
Urge to kill: Rising
-
Weeks of struggling with these weird things have finally been solved.
JTables - How do they work?
JTables are the greatest creation in the history of the Java universe. They are also the least understood with the most frustrating application programming interface and incredibly unhelpful 'help' and 'how to use' from the Sun Java site.
In short:
1. Setup Column Names. e.g String[]columnNames={"Age","Sex","Location"};
2. Create a javax.swing.DefaultTableModel for the JTable.
3. Add the Columns/Fields to the DefaultTableModel.
4. Create a new JTable containing the DefaultTableModel.
/**
* This method creates the columns for a table given an Array of Column Names
*/
public static DefaultTableModel createTable(String[]cn){
DefaultTableModel dtm=new DefaultTableModel();
for(int i=0;i<cn.length;i++){
dtm.addColumn(cn[i]);
}//4 column names
return dtm;
}//me
Followed by:
JTable table=new JTable(createTable(columnNames));
And DONE! Table DONE! You will now have a blank Table. BUT: There are two very serious problems.
1. The Table Column Names are not displayed!! :sad face:
2. Table is empty.
To fix problem (1) you must, Must, MUST put the Table into a JScrollPane. I dont know why, but you just have to.
JScrollPane scroll=new JScrollPane(table);
Then you must add this to whatever Container (JPanel or whatever) you are using. DO NOT add the JTable directly to the container.
My Table is still empty!
This is easy to fix. Grab the DefaultTableModel out of the JTable and add a row to it like so:
DefaultTableModel dtm=(DefaultTableModel)table.getModel();
Object[]rowData={new Integer(106),"Male","GetSome Forums"};
dtm.addRow(rowData);
And you are DONE! You can even put whole Class Objects into the row data, but be aware that a Table is not 'connected' in anyway. If you have, say, a row which has a Computer and a Computer price, updating the Computer objects price will not update the price displayed in the Computer Price column.
This makes updating abit of a pain, BUT if you are using the JTable as a display for a database then you should already be updating the table as soon as any changes are made. Have fun!
-
A few rules about Applets
1. Dont use JApplets.
2. Dont use Canvas.
3. If you break either rule 1 or rule 2, do not use Canvas with JApplet, use java.applet.Applet instead.
4. You cannot read directories.
5. If you need to read a directory, dont bother. It is a massive headache inducing task.
6. If you break rule 4 or rule 5 then use getCodeBase() and append a URL or "\\" or "\\\" or "\\\\" to the required filepath.
Finally: Always try to keep files required as a CLASS file (like text files and stuff) and never read items out of a JAR file.
Consider yourself warned.
-
Don't use Java
Class dismissed.
-
Don't use Java
(http://www.getsome.co.nz/attachment.php?attachmentid=6652&stc=1&d=1324351506)
Class dismissed.
(http://www.politicsforum.org/images/flame_warriors/target.jpg)
Target is the guy everyone in a forum loves to hate. To some degree he brings this upon himself. For example, he may be a known cheater in a game forum, a conservative among liberals, a WindowsMICROSOFT guy among Mac Java[/size] enthusiasts
-
Programming zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
-
I didn't think such thing as a java enthusiast existed.
-
Applets and Timings
Please note that Applets and JApplets run at approximately five times faster than a JNLP or Desktop application, that is to say: Threads, For Loops, and delays must be increased by at least five times to achieve the same effect that the desktop tests run at.
Also: Graphical Interfaces cannot be 'restarted', nor can ArrayLists be altered in a graphical environment, even if it is an extended class. Items cannot be added into an Objects list, only removed.
That is all.
-
I didn't think such thing as a java enthusiast existed.
ikr.
-
Do not extend GUI Swing JComponents or any java.awt.Component for that matter and more than a few (<4) Data Members. If you do need to include more than a small number of variables (e.g more than JButton.pressed=true/false and so forth) then create a Data Member Reference to an Object instead ('Global Variable Pointer' for you C types).
If you give too many Data Members then the Object will not draw correctly. Example below:
public class NarutoChessPiece extends JButton{
protected char type;
protected String name="Empty Square";
protected boolean turn=false;
protected boolean empty=true;
protected boolean moveMe=false;
protected boolean player1=false;
protected int x;
protected int y;
}
Will not draw in a correct order from a two dimensional array for a board. By creating a Class, say 'NarutoPiece' and the moving all the Data Members from the above class into the NarutoPiece class all problems disappear.
Except for User Error which can only be eliminated with bullets or education.
-
You should can Java and go to C# :P
-
-#
-
+ ++
-
([url]http://www.getsome.co.nz/attachment.php?attachmentid=6652&stc=1&d=1324351506[/url])
Writing software for parking meters is a serious business.
while ( myWallet.Money > 0)
{
EatMoreMoney(moreMoney);
System.out.println("Om Nom Nom!");
}
-
Writing software for parking meters is a serious business.
while ( myWallet.Money > 0)
{
EatMoreMoney(moreMoney);
System.out.println("Om Nom Nom!");
}
You bastard! I can't believe you'd write that code to steal my monies. I'm just glad you haven't figured out how to charge my cc yet...
-
I can only charge your credit card if you don't give me your number.
-
Writing software for parking meters is a serious business.
while ( myWallet.Money > 0)
{
EatMoreMoney(moreMoney);
System.out.println("Om Nom Nom!");
}
Thats not how the system works!
public class Bank extends Thief{
protected final ArrayListsuckers;
protected double phatLewts=0;
public Bank(ArrayListcustomers){
suckers=customers;
}//constructor
public void depositMoney(Customer sucker){
if(sucker.hasMoney()){
phatLewts=phatLewts+sucker.getMoney();
sucker.setMoney(0);
}//fi
}//method Take their money and laugh
}//class
-
Writing software for Java VMs is a serious business.
while ( myDevice.Memories > 0)
{
EatMoreMemory(moreMemory);
System.out.println("Om Nom Nom!");
}
I've so totally busted your elaborate ruse.
-
Do not extend GUI Swing JComponents or any java.awt.Component for that matter and more than a few (<4) Data Members. If you do need to include more than a small number of variables (e.g more than JButton.pressed=true/false and so forth) then create a Data Member Reference to an Object instead ('Global Variable Pointer' for you C types).
If you give too many Data Members then the Object will not draw correctly. Example below:
Will not draw in a correct order from a two dimensional array for a board. By creating a Class, say 'NarutoPiece' and the moving all the Data Members from the above class into the NarutoPiece class all problems disappear.
OH! I found out why this was happening.
There are methods in the Component & JComponent called:
setX(int num)
setY(int num)
IF YOU OVERRIDE THESE IN ANY WAY EVERYTHING BREAKS.
Never override these methods. Create a new method instead, like "setXX(int n)" or "setYCoordinate".
If you override the methods then the Swing's draw X & Y coordinates become a weird number.
Dont forget to change the getX() and getY() to something like "getXX()" and "getYY()".
-
Then you could make a method miosis() to split your co-ordinates?
-
http://www.youtube.com/watch?v=Oo-cIGVaOYE
-
lol epic
-
So old, but still good.
gOLDen, one might say :P
-
Dont forget the two required imports!
import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;
/**
Apparently getMethod does not allow for protected method access, but getDeclaredMethod does
*/
public void actionPerformed(ActionEvent ae){
try{
getClass().getDeclaredMethod(ae.getActionCommand()).invoke(this);
}//catch
catch(Exception e){
javax.swing.JOptionPane.showMessageDialog(null,e.toString(),ae.getActionCommand(),javax.swing.JOptionPane.INFORMATION_MESSAGE);
}//catch
}//me action performed
-
For some reason KeyEvents (http://docs.oracle.com/javase/1.5.0/docs/api/java/awt/event/KeyEvent.html) refuse to work properly. For example:
public void keyTyped(KeyEvent e) {
if(e.getKeyChar()==KeyEvent.VK_ESCAPE){
System.exit(0);
}//if you press escape (keyChar 27)
}//me
May or may not work. HOWEVER:
public void keyTyped(KeyEvent e) {
if(e.getKeyChar()==[b]e[/b].VK_ESCAPE){
System.exit(0);
}//if you press escape (keyChar 27)
}//me
DOES work even though KeyEvent key codes are static ints. This may be related to keyboard layout.
You have been warned
-
What happens if you use getKeyCode() instead of getKeyChar()
-
still on 1.5...oh dear
Don't upgrade to Juno, Juno is a bad upgrade over Helios/Indigo unless you turn off all validators, then it becomes quite usable.
Going to dabble in android apps over summer break, have been in spring mvc + hibernate/jpa for way too long
-
Tiwa doesn't use real IDE's.
He uses the glorified notepad that is BlueJ :)
On the same note, just upgraded from Galileo to Helios at work because it was balls.
-
This thread is intense.
-
You're in tents.
-
I pitch tents every night.
-
I pitch tents every night.
About Java code?
-
Actually, no.
-
If you have a JPanel or some kind of GUI Container and would like to completely CHANGE (i.e JPanel displayPanel=new JPanel()) the container then you must do the following:
a) Remove the component from the container i.e remove(displayPanel)
b) change the component to what you want i.e displayPanel=new JPanel()
c) add the changed component back to the container i.e add(displayPanel)
d) validate or pack the container
This is a quick and dirty way to do it. The actual way to do it is to ensure the event dispatch is set to update the parent container on change followed by blah blah blah blah blah changnesia.
-
For those that never see it nor use it or have heard of bitwise operations, this is great boolean operator:
a |= b;
is the same as
a = a || b;
It's a bitwise inclusive or assignment, use it all the time myself to make lines more readable, but have found fellow developers have never seen it. Now you have.
IE:
canHasCheeseBurger |= hasEnoughMoney;
canHasCheeseBurger = canHasCheeseBurder || hasEnoughMoney;
-
ok, that's cool.
Does &= work as well?
-
For those that never see it nor use it or have heard of bitwise operations, this is great boolean operator:
a |= b;
is the same as
a = a || b;
It's a bitwise inclusive or assignment, use it all the time myself to make lines more readable, but have found fellow developers have never seen it. Now you have.
IE:
canHasCheeseBurger |= hasEnoughMoney;
canHasCheeseBurger = canHasCheeseBurder || hasEnoughMoney;
You should probably change that to what it actually is, as to avoid confusion for the people that attempt to use it for other types, not sure who would attempt to use it in this way for any other types except booleans though.
a |= b;
is the same as
a = a | b;
But because booleans are 0x0 and 0x1, a bitwise OR is equivalent to a logical OR.
I do agree it is a nice code shortcut, but sometimes I think the format a = a || b can be more readable. There is no advantage of using one over the other at a performance level, it comes down to personal taste :)
@SpaceMonkey: Yes, yes it does.
-
For those that never see it nor use it or have heard of bitwise operations, this is great boolean operator
Java indeed contains bitwise operators:
http://docs.oracle.com/javase/tutorial/java/nutsandbolts/op3.html
and yes: Most people are never taught them. They are meant to flow on from the simple mathematical logic learned from Karnaugh maps (http://commons.wikimedia.org/wiki/Logic_diagram#Karnaugh_maps). Unfortunately: That is no longer a requirement.
The Java programming language also provides operators that perform bitwise and bit shift operations on integral types. The operators discussed in this section are less commonly used. Therefore, their coverage is brief; the intent is to simply make you aware that these operators exist.
The unary bitwise complement operator "~" inverts a bit pattern; it can be applied to any of the integral types, making every "0" a "1" and every "1" a "0". For example, a byte contains 8 bits; applying this operator to a value whose bit pattern is "00000000" would change its pattern to "11111111".
The signed left shift operator "<<" shifts a bit pattern to the left, and the signed right shift operator ">>" shifts a bit pattern to the right. The bit pattern is given by the left-hand operand, and the number of positions to shift by the right-hand operand. The unsigned right shift operator ">>>" shifts a zero into the leftmost position, while the leftmost position after ">>" depends on sign extension.
The bitwise & operator performs a bitwise AND operation.
The bitwise ^ operator performs a bitwise exclusive OR operation.
The bitwise | operator performs a bitwise inclusive OR operation.
The following program, BitDemo, uses the bitwise AND operator to print the number "2" to standard output.
class BitDemo {
public static void main(String[] args) {
int bitmask = 0x000F;
int val = 0x2222;
// prints "2"
System.out.println(val & bitmask);
}
}
-
It's a given that code should be readable. Just as important though is understanding operators.
E: I'm going to go test something
-
What test? Hows it going?
-
Just searched my entire subversion repository for uses of bitwise operators to see who and what usage there is, wasn't very interesting, only my projects have them and only I use them.
-
Yeah, bit logic isn't very common place in OOP. It kind of defeats the purpose of OOP, most situations you you bitwise operators you can replace it with inheritance or the likes.
The biggest use I see for bitwise is flags.
eg
enum Direction
{
North = 0x1,
South= 0x10,
East = 0x100,
West = 0x1000
}
Where you can easily figure what direction someone is travelling. Assigning here is weird though..
Direction SpaceMonkey = Direction.North;
SpaceMonkey |= Direction.South;
System.out.println(SpaceMonkey); //SpaceMonkey does the moonwalk.
-
I read the Wiki article on Bitwise operation.
I don't see the point of it. In what real world situations would this be useful?
-
IIRC it's a legacy thing from when performance was very important and using floats/doubles were the norm. F**k I hate floats.
If I am not mistaken, bitwise operations actually occur under the hood for normal operations, hence 3GL and 4GL languages don't need bitwise operators.
-
I read the Wiki article on Bitwise operation.
I don't see the point of it. In what real world situations would this be useful?
WTF, not sure if srs.
-
Fuck yes, my whole team can related to almost every single one:
http://martinvalasek.com/blog/pictures-from-a-developers-life
-
^ Love it.
-
If, for some reason, you would like to make an image using text which contains a specialised font, you can do so in the following manner.
If you do this, then you can add the ImageIcon to a JButton and set the ActionCommand or Text to be a String.
This is one way to avoid the use of a customised JButton if you are using it to store a String as opposed to a full blown object.
protected ImageIcon createIcon(int w,int h,AttributedString line){
public void createButtons(){
String[]HAND_SIGNS={"Fingers","Palm","Snap","Wave","Digit","Clap"};
AttributedString[]letters = new AttributedString[HAND_SIGNS.length];
Font font2 = new Font("Monotype Corsiva", Font.BOLD, 50);
for(int i=0;i<HAND_SIGNS.length;i++){
AttributedString a=new AttributedString(HAND_SIGNS[i].substring(0,1));
a.addAttribute(TextAttribute.FONT, font2);
letters[i]=a;
}//4 hand_signs.length
JButton[]btns=new JButton[letters.length];
int w=100;
for(int i=0;i<btns.length;i++){
JButton btn=new JButton(createIcon(w,w,letters[i]));
btn.setPreferredSize(new Dimension(w,w));
btns[i]=btn;
btn.setActionCommand(String.format("btn%s",HAND_SIGNS[i]));
//btn.addActionListener(this);
btns[i]=btn;
}//4 btns.length
}//method create buttons
protected ImageIcon createIcon(int w,int h,AttributedString line){
BufferedImage image=new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB);
Graphics g = image.createGraphics();
g.setColor(Color.BLACK);
g.fillRect(0,0,w,h);
g.setColor(Color.WHITE);
g.drawString(line.getIterator(),25,70);//given a w=100,h=100: font size=50
return new ImageIcon(image);
}//me createIcon
If I am not mistaken, bitwise operations actually occur under the hood for normal operations, hence 3GL and 4GL languages don't need bitwise operators.
Yep. You should use them in PHP though, but since this is not a PHP thread, that observation is irrelevant.
Fuck yes, my whole team can related to almost every single one:
[url]http://martinvalasek.com/blog/pictures-from-a-developers-life[/url]
Genki Sudo and Singham. That is amazing.
-
Why is it called a JButton? Why not just a Button? Why does Java have to put a J in front of Jeverything?
-
Java uses Time in a surprisingly obscure manner. The Time class is actually the java.sql.Time package which wraps a java.util.Date class. This means the default 'Time' is set to January 1, 1970 and the 'Time' is actually the number of milliseconds since January 1, 1970 (http://docs.oracle.com/javase/6/docs/api/java/sql/Time.html)
One of your best bets at using the Time class is to create your own Object which surpresses the Deprecated Time Constructor
Time(int hour, int minute, int second) - Deprecated. Use the constructor that takes a milliseconds value in place of this constructor
class TimeIndex extends java.sql.Time{
// int hours;
// int minutes;
// int seconds;
// @SuppressWarning("deprecated")
protected int milliseconds;
@SuppressWarnings("deprecation")
public TimeIndex(){
super(0,0,0);
}//c
public int getMilliseconds(){
return milliseconds;
}
public void setMilliseconds(int n){
if(n>999)n=0;
milliseconds=n;
}
// public int getSeconds(){
// return seconds;
// }
public String toString(){
return String.format("%s,%d",super.toString(),milliseconds);
}//toString
}//class
Why is it called a JButton? Why not just a Button? Why does Java have to put a J in front of Jeverything?
Why does C# use 'using' instead of import?
Why does everyone say "Smorgasbord" instead of the correct "Smörgåsbord"?
Why does everyone outside of Deustchland called it Germany, and everyone outside of Sverige and Danmark call it "Sweden" and "Denmark"?
-
Fuck yes, my whole team can related to almost every single one:
[url]http://martinvalasek.com/blog/pictures-from-a-developers-life[/url]
Most of them copied from:
http://devopsreactions.tumblr.com/
-
In random developer news, I installed an incorrect crontab last night which resulted in a call from the georgian government this morning inquiring about a possible cyber-attack.
I hope to not go to jail :P
-
When testing an application it is usually important to read files from a Hard Drive or Local Resource.
An easy way to do this is by creating an Object that reads the and stores the names of files held in a directory
import java.io.File;
public class DirectoryReader{
private String path;
private String[]files;
public DirectoryReader(){
}//constructor
public DirectoryReader(String path){
try{
this.path=path;
File folder = new File(path);
File[] listOfFiles = folder.listFiles();
files=new String[listOfFiles.length];
for (int i = 0; i < listOfFiles.length; i++) {
if (listOfFiles[i].isFile()) {
files[i]=listOfFiles[i].toString();
}//if
}//for
}catch(NullPointerException npe){
javax.swing.JOptionPane.showMessageDialog(null,npe .toString(),"Directory empty or does not exist!",javax.swing.JOptionPane.INFORMATION_MESSAGE);
}//method
}//constructor
public String[] getImages(){
return getFiles();
}//method
public String[] getFiles(){
return files;
}//method
public int getSize(){
return getLength();
}//method
public int getLength(){
return files.length;
}//method
public String toString(){
return "I am an object which can read directories!";
}//method
}//class
You must be aware that this Object cannot be used in a Web Based environment, but is easily replaced by code which reads the contents of Local Web Resources (any resource located on the same Web Domain) OR the contents of an applications Jar file
Programming zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzz
http://www.youtube.com/watch?feature=player_embedded&v=nKIu9yen5nc
I didn't think such thing as a java enthusiast existed.
They're as rare as Chaotic Neutral Paladins (http://www.giantitp.com/forums/showthread.php?t=112538)
Vessel: The vessel is chosen (whether by a deity or institution) for their paladin abilities. They are typically already martially proficient, or if they are not then they are typically trained to be so. Vessels have their own alignment however they must follow the whim of whoever granted them their abilities (which usually goes by a code of conduct similar to that of the zealot) or lose them altogether (fallen). Unlike the zealot, a vessel's abilities do not correspond to their alignment.
CN - Chaotic Neutral paladins are identical to the chaotic good paladin listed above, with the addition that their smite is identical to the true neutral paladin's in how it functions.
-
whoops
(http://s3.postimage.org/huzvr7g6b/traffic2.png)
-
You have a heavy flow there Bell.
-
The part between about 11pm and 6am is when I crashed a government server. At around 9 they blocked the machines IP address.
I believe i'll be called into a meeting with the government tomorrow....
-
I'm talking half a days leave today.
This will be me after lunch.
(http://www.topito.com/wp-content/uploads/2013/01/code-13.gif)
-
In random developer news, I installed an incorrect crontab last night which resulted in a call from the georgian government this morning inquiring about a possible cyber-attack.
I hope to not go to jail :P
Oh deployments before leaving.
I always dread pushing the boat out on friday afternoons then coming back on monday to some kind of angry shitstorm.
-
A major part of the project i'm working on involves this awesome scraper thing I made that rips a large data set from a government website reasonably fast.
I was setting up a cron job to automatically run the scraper every night at 9pm but I made an oopsy.
* 21 * * * /var/data/scraper/perform_scrape > /var/data/scraper/allout.txt 2>&1
So at 9pm that night I was simulantously drinking wine at a friends birthday dinner at a nice resturant and beginning a 12 hour long 'cyber-attack' on the georgian government.
So I'm pretty much James Bond.
-
So I'm pretty much James Bond.
It is true.
You are exactly like Timothy Dalton
edit: It is common knowledge that you can insert a collection directly into a HashSet or ArrayList. However: You can convert an Array into list on the fly and add it
String[]effects={"range","duration","attack","defence"};
String[]jrange={"tori","inu","nezumi"};
String[]jdef={"hebi","ii"};
String[]jatk={"tora","uma","saru"};
String[]jtime={"ushi","tatsu","u"};
ArrayList<HashSet<String>>sets=new ArrayList<HashSet<String>>();
sets.add(new HashSet<String>(Arrays.asList(jrange)));
sets.add(new HashSet<String>(Arrays.asList(jtime)));
sets.add(new HashSet<String>(Arrays.asList(jatk)));
sets.add(new HashSet<String>(Arrays.asList(jdef)));
HashMap<String,HashSet<String>>map=new HashMap<String,HashSet<String>>();
for(int i=0;i<effects.length;i++){
map.put(effects[i],sets.get(i));
}
However: What you CANNOT do is the following
ArrayList>sets=new ArrayList>(new HashSet[]{
new HashSet(Arrays.asList(jrange)),
new HashSet(Arrays.asList(jtime)),
new HashSet(Arrays.asList(jatk)),
new HashSet(Arrays.asList(jdef))
});
This leads to a Generic Array Creation error on compile. There is no way to circumvent this. Just be aware that it exists
-
mod_slotlimit
-
Although there is no documented way to kill a thread, an undocumented feature of Java is if you set a thread to null then memory allocation is instantly free for use by the program and does not require the Garbage Collector call
Please be aware that there is no way to 'restart' a thread in Java
I didn't think such thing as a java enthusiast existed.
Someone needs to learn the 13 Programmer Personality Types methinks
http://www.javaworld.com/article/2078524/mobile-java/programmer-personality-types--13-profiles-in-code.html (http://www.javaworld.com/article/2078524/mobile-java/programmer-personality-types--13-profiles-in-code.html)
My type is number 9: The True Believer
Programming personality type No. 9: The True Believer
Did you know that the best way to run Ruby is with Java? The Java devotees will tell you this in case you're thinking. The C lovers know that it would run faster than a Ferrari if someone would rewrite it in C because that's the only way to "get close to the metal."
It usually seems moderately funny to set up a lunch with a Python lover and C devotee and watch them snipe at each other for an hour.
Car: Anything with a sticker showing Calvin peeing on the competition
Relationship status: Married to the one who should have led the homecoming parade
Household chore: Putting up flags for holidays
Role model: Richard Stallman or Steve Jobs or ....
Pet: "He won 'Best in Show' in 2009 and 2010."
Favorite programming construct: Sit down first and ask
Drink: It's tattooed on their arm
-
I'd like to say I too am also a #9... but realistically I'll have to say I'm probably a Duct taper.
I just reimplemented that heap of shit that was so popular because everyone on the internet is so damn retarded: code igniter.
In SilverStripe. Because I want to actually have classes I can fucking INHERIT from. Y'know... that pretty much the entire point of them. Oh and (easily) have more than one instance of. That isn't a fucking pseudo global variable.
... But I coudln't be fucked rewriting the entire legacy app. So I wrote a translation proxy. It seemed easier. And now I can use a proper fucking view layer.
And I did work on an N64 emulator for a bit once...
Because C is the truth of the world.
-
The \n function in Java no longer works as a universal new line character.
Use one of the following:
String.format("%n")
System.getProperty("line.separator")
System.getProperty is universal
Thank you
-
The \n function in Java no longer works as a universal new line character.
Use one of the following:
String.format("%n")
System.getProperty("line.separator")
System.getProperty is universal
Thank you
What an awful change... That's going to require massive change.
And surely they could've at least made getting the new character easier. Say.... Environment.NewLine
-
The \n function in Java no longer works as a universal new line character.
Thank you
What an awful change... That's going to require massive change.
And surely they could've at least made getting the new character easier. Say.... Environment.NewLine
The \n function works, it just does not seem to work when you try saving to a text file.
I have no idea why. For example:
Absolute monarchy\nA form of government where the monarch rules unhindered, i.e., without any laws, constitution, or legally organized oposition.Is being saved as
Absolute monarchyA form of government where the monarch rules unhindered, i.e., without any laws, constitution, or legally organized oposition.This is happens when you use the file writer e.g
fileWriter.write("Absolute monarchy\nA form of government where the monarch rules unhindered, i.e., without any laws, constitution, or legally organized oposition.");
-
The \n function in Java no longer works as a universal new line character.
Thank you
What an awful change... That's going to require massive change.
And surely they could've at least made getting the new character easier. Say.... Environment.NewLine
The \n function works, it just does not seem to work when you try saving to a text file.
I have no idea why. For example:
Absolute monarchy\nA form of government where the monarch rules unhindered, i.e., without any laws, constitution, or legally organized oposition.Is being saved as
Absolute monarchyA form of government where the monarch rules unhindered, i.e., without any laws, constitution, or legally organized oposition.This is happens when you use the file writer e.g
fileWriter.write("Absolute monarchy\nA form of government where the monarch rules unhindered, i.e., without any laws, constitution, or legally organized oposition.");
You probably need to escape it somehow?
-
You probably need to escape it somehow?
The backslash is escaping it. '\n' is a line feed, or more commonly "new line"
The whole thing looks like a bit of balls up. Back when I did Java \n worked fine for files. I used \r\n for "safety", but meh.
Out of interest what OS were you on? Should also try running the same code against an older VM see when they "broke" it.
Also Tiwa, this is why you should most definitely move to C# :P
-
You probably need to escape it somehow?
The backslash is escaping it. '\n' is a line feed, or more commonly "new line"
The whole thing looks like a bit of balls up. Back when I did Java \n worked fine for files. I used \r\n for "safety", but meh.
Out of interest what OS were you on? Should also try running the same code against an older VM see when they "broke" it.
Also Tiwa, this is why you should most definitely move to C# :P
I never use \n. I was running a test on a file that listed government types to see if I could convert it to a "Government.name\nGovernment.text" but the text file came out all wrong.
I've attached the government text file if anyone wants it. They're all the real world government systems. line.substring(0,line.indexOf(" - ")) works fine to get the name. Of course you should save the index of line.indexOf but I shouldnt have to tell you such things.
OS: Windows XP, also affects Windows Vista and Windows 7 and Windows 8.
It really isnt a big deal. I usually use an sql database instead of text files
-
The backslash is escaping it. '\n' is a line feed, or more commonly "new line"
I know what a newline is Xeno.. I was troubleshooting PC's when you were still in your dads ballbag ;D I'm actually old enough to remember using dot matrix and line printers where these sort of things were quite relevant :-P
What I mean is that the \n is clearly being discarded/ignore by the filewriter.write. If the output Tiwa posted is accurate,it's not processing it, or passing it through, it's simply ignoring it. I don't Java,but that suggests to me that somehow it needs to be escaped an additional degree so that whatever logic in the filewriter.write statement is formatting it, doesn't interpret it and format it.
Does that make sense?
-
What I mean is that the \n is clearly being discarded/ignore by the filewriter.write. If the output Tiwa posted is accurate,it's not processing it, or passing it through, it's simply ignoring it. I don't Java,but that suggests to me that somehow it needs to be escaped an additional degree so that whatever logic in the filewriter.write statement is formatting it, doesn't interpret it and format it.
Does that make sense?
I think I found out what the problem is. Those mofo's at Oracle added a new Package which includes new Charsets. The \n encoding is no longer default and I cant seem to load that java.nio.charset package at all. The obvious solution is to use a delimiter which is not a newline, which is what I do anyway. I am pretty sure decisions like these are what caused James Gosling to stop being a consultant for Java
-
The backslash is escaping it. '\n' is a line feed, or more commonly "new line"
I know what a newline is Xeno.. I was troubleshooting PC's when you were still in your dads ballbag ;D I'm actually old enough to remember using dot matrix and line printers where these sort of things were quite relevant :-P
What I mean is that the \n is clearly being discarded/ignore by the filewriter.write. If the output Tiwa posted is accurate,it's not processing it, or passing it through, it's simply ignoring it. I don't Java,but that suggests to me that somehow it needs to be escaped an additional degree so that whatever logic in the filewriter.write statement is formatting it, doesn't interpret it and format it.
Does that make sense?
No, no. I think you misunderstood. \n represents a "new line" and the backslash is the escape character.
;D 8) ;D 8)
-
this is why i hate java, even worse when i am doing c# dev at work but then the have to consult on another team that uses a JS runtime template processor that is used to inject values into sql templates and then that is running on a JVM.
its like a clusterfuck of ooops
-
I'm so sorry for those of you that have to look at Java
I send my condolences
-
(http://iforce.co.nz/i/xwt4ys5l.kja.jpg)
-
I don't Java,but that suggests to me that somehow it needs to be escaped an additional degree so that whatever logic in the filewriter.write statement is formatting it, doesn't interpret it and format it.
No, no. I think you misunderstood. \n represents a "new line" and the backslash is the escape character.
[/quote]
You know exactly what I mean xeno :-P
I know it's an escape character hence saying it needs to be escaped an additional degree.. the escape character needs to be escaped via (whatever java does to escape such things) so that it's parsed through rather than being escaped, interpreted and apparently ignored by the logic in the filewriter.write thing.
Like in Bash you'd either enclose it in '\n' or double escape it like \\n (or perhaps the n might need escaping too like \\\n I'd have to check)
-
Lias .. you should know you have to Bash before they escape not after.