What complexity are the methods multiply, divide and pow in BigInteger currently? There is no mention of the computational complexity in the documentation (nor anywhere else).
I am trying to create a database of users with connection between users (friends list).
There are 2 main tables: UserEntity (main field id) and FriendEntity with fields:
- initiatorId - id of user who initiated the friendship
- friendId - id of user who has been invited.
Now I am trying to fetch all friends of one particular user and encountered some problems with using subqueries in JDO here.
Logically the query should be something like this:
SQL: SELECT * FROM UserEntity WHERE EXISTS (SELECT * FORM FriendEntity WHERE (initiatorId == UserEntity.id && friendId == userId) || (friendId == UserEntity.id && initiatorId == userId))
or SELECT * FROM UserEntity WHERE userId IN (SELECT * FROM FriendEntity WHERE initiatorId == UserEntity.id) OR userId IN (SELECT * FROM FriendEntity WHERE friendId == UserEntity.id)
So to replicate the last query in JDOQL, I tried to do the following:
Query friendQuery = pm.newQuery(FriendEntity.class);
friendQuery.setFilter("initiatorId == uidParam");
friendQuery.setResult("friendId");
Query initiatorQuery = pm.newQuery(FriendEntity.class);
initiatorQuery.setFilter("friendId == uidParam");
initiatorQuery.setResult("initiatorId");
Query query = pm.newQuery(UserEntity.class);
query.setFilter("initiatorQuery.contains(id) || friendQuery.contains(id)");
query.addSubquery(initiatorQuery, "List initiatorQuery", null, "String uidParam");
query.addSubquery(friendQuery, "List friendQuery", null, "String uidParam");
query.declareParameters("String uidParam");
List<UserEntity> friends = (List<UserEntity>) query.execute(userId);
In result I get the following error:
Unsupported method while parsing expression.
Could anyone help with this query please?
i want to know how to get the string from group of string
String j = "<a href=\"/watch?v=4Qx-lBqOqiQ&feature=popular\" onclick=\"\" onmousedown=\"yt.analytics.urchinTracker(\'/Events/Home/PersonalizedHome/POP/Logged_Out');\" ><span class=\"video-thumb video-thumb-220 \" id=\"video-thumb-4Qx-lBqOqiQ-8821469\"><img src=\"http://i1.ytimg.com/vi/4Qx-lBqOqiQ/hqdefault.jpg\" class=\"vimg220\" alt=\"Dog Squirrel Chasing A Squirrel\" title=\"Dog Squirrel Chasing A Squirrel\" onclick=\";yt.www.watch.watch5.IEshenanigans(event, this)\"><span class=\"video-time\"><span>1:08</span></span><span class=\"video-actions\"><button class=\"yt-uix-button-short yt-uix-button yt-uix-button-arrowbutton\" onclick=\"; return false;\" type=\"button\"> <img class=\"yt-uix-button-arrow\" src=\"http://s.ytimg.com/yt/img/pixel-vfl73.gif\" alt=\"\"> hai</a>";
i want to get the string href=\"/watch?v=4Qx-lBqOqiQ&feature=popular\" and src=\"http://i1.ytimg.com/vi/4Qx-lBqOqiQ/hqdefault.jpg\"
thanks and advance
when looping, for instance:
for ( int j = 0; j < 1000; j++) {}; and I need to instantiate 1000 objects, how does it differ when I declare the object inside the loop from declaring it outside the loop ??
for ( int j = 0; j < 1000; j++) {Object obj; obj =}
vs
Object obj;
for ( int j = 0; j < 1000; j++) {obj =}
It's obvious that the object is accessible either only from the loop scope or from the scope that is surrounding it. But I don't understand the performance question, garbage collection etc.
What is the best practice ? Thank you
Dear All:
Was wondering, which is correct:
Option One
class A {
public void methodOne() {
synchronized(this) {
modifyvalue
notifyAll()
}
}
public void methodTwo() {
while (valuenotmodified) {
synchronized(this) {
wait()
}
}
}
Option Two
class A {
public void methodOne() {
modifyvalue
synchronized(this) {
notifyAll()
}
}
public void methodTwo() {
while (valuenotmodified) {
synchronized(this) {
wait()
}
}
}
and why?
Thank you
Misha
how are static method calls handled by the JVM? does it still allocate memory when a call is made? if yes, how does garbage collection treat this allocation after the method call?
I need to split a text using the separator ". ". For example I want this string :
Washington is the U.S Capital. Barack is living there.
To be cut into two parts:
Washington is the U.S Capital.
Barack is living there.
Here is my code :
// Initialize the tokenizer
StringTokenizer tokenizer = new StringTokenizer("Washington is the U.S Capital. Barack is living there.", ". ");
while (tokenizer.hasMoreTokens()) {
System.out.println(tokenizer.nextToken());
}
And the output is unfortunately :
Washington
is
the
U
S
Capital
Barack
is
living
there
Can someone explain what's going on?
Hi,
I have an arraylist set up. I have input instuctions set up too, so that the user can enter one string, then one integer, then one string (the first name, the age, and the last name).
I need to sort the arraylist by the last name. The code I have entered so far is all under the main method:-
public static void main(String[] args) {
Name Name[] = new Name[50];
int count = 0;
for (int i=0; i<50; i++)
NewName[i] = new Name();
//ADD NEW TO ARRAYLIST NAME
String FName = JOptionPane.showInputDialog("first name");
int age = Integer.parseInt(JOptionPane.showInputDialog("age"));
String LName = JOptionPane.showInputDialog("last name");
NewName[count] = new Name(FName, age, LName);
count = count++;
}
//ITEMS SORT BY LAST NAME
//CODE FOR SORT GOES HERE
I am relatively new to multi-threading and want to execute a background task using a Swingworker thread - the method that is called does not actually return anything but I would like to be notified when it has completed.
The code I have so far doesn't appear to be working:
private void crawl(ActionEvent evt)
{
try
{
SwingWorker<Void, Void> crawler = new SwingWorker<Void, Void>()
{
@Override
protected Void doInBackground() throws Exception
{
Discoverer discover = new Discoverer();
discover.crawl();
return null;
}
@Override
protected void done()
{
JOptionPane.showMessageDialog(jfThis, "Finished Crawling", "Success", JOptionPane.INFORMATION_MESSAGE);
}
};
crawler.execute();
}
catch (Exception ex)
{
JOptionPane.showMessageDialog(this, ex.getMessage(), "Exception", JOptionPane.ERROR_MESSAGE);
}
}
Any feedback/advice would be greatly appreciated as multi-threading is a big area of programming that I am weak in.
I have the following code in struts.xml:
<interceptor-ref name="checkTabsStack">
<param name="tabName">availability</param>
</interceptor-ref>
and I want to access the parameter tabName in the interceptor routine, how do i do that? i tried
Map params = ActionContext.getContext().getParameters();
but params comes empty...
Thanks!
Here's what I am looking to accomplish, I have a class that has an enum of some values and I want to subclass that and add more values to the enum. This is a bad example, but:
public class Digits
{
public enum Digit
{
0, 1, 2, 3, 4, 5, 6, 7, 8, 9
}
}
public class HexDigits extends Digits
{
public enum Digit
{
A, B, C, D, E, F
}
}
so that HexDigits.Digit contains all Hex Digits. Is that possible?
hi,
need to convert a pdf file to a doc file. I found different type of example to generate pdf file but not got pdf to doc.
please help me in this regard with good example or source code or guideline.
Right, this is from an older exam which i'm using to prepare my own exam in january. We are given the following method:
public static void Oorspronkelijk()
{
String bs = "Dit is een boodschap aan de wereld";
int max = -1;
char let = '*';
for (int i=0;i<bs.length();i++) {
int tel = 1;
for (int j=i+1;j<bs.length();j++) {
if (bs.charAt(j) == bs.charAt(i)) tel++;
}
if (tel > max) {
max = tel;
let = bs.charAt(i);
}
}
System.out.println(max + " keer " + let);
}
The questions are:
what is the output? - Since the code is just an algorithm to determine the most occuring character, the output is "6 keer " (6 times space)
What is the time complexity of this code?
Fairly sure it's O(n²), unless someone thinks otherwise?
Can you reduce the time complexity, and if so, how?
Well, you can. I've received some help already and managed to get the following code:
public static void Nieuw()
{
String bs = "Dit is een boodschap aan de wereld";
HashMap<Character, Integer> letters = new HashMap<Character, Integer>();
char max = bs.charAt(0);
for (int i=0;i<bs.length();i++) {
char let = bs.charAt(i);
if(!letters.containsKey(let)) {
letters.put(let,0);
}
int tel = letters.get(let)+1;
letters.put(let,tel);
if(letters.get(max)<tel) {
max = let;
}
}
System.out.println(letters.get(max) + " keer " + max);
}
However, I'm uncertain of the time complexity of this new code: Is it O(n) because you only use one for-loop, or does the fact we require the use of the HashMap's get methods make it O(n log n) ?
And if someone knows an even better way of reducing the time complexity, please do tell! :)
When I run the following code it triggers an error message. The error message is shown below the code.
What code changes, or changes to the image file, are needed to fix this error?
Help will be appreciated.
import java.awt.*;
import java.awt.datatransfer.*;
public class LoadToClipboard {
public static void main( String [] args ) {
Toolkit tolkit = Toolkit.getDefaultToolkit();
Clipboard clip = tolkit.getSystemClipboard();
clip.setContents( new ImageSelection( tolkit.getImage("StackOverflowLogo.png")) , null );
}
}
class ImageSelection implements Transferable {
private Image image;
public ImageSelection(Image image) {
this.image = image;
}
// Returns supported flavors
public DataFlavor[] getTransferDataFlavors() {
return new DataFlavor[]{DataFlavor.imageFlavor};
}
// Returns true if flavor is supported
public boolean isDataFlavorSupported(DataFlavor flavor) {
return DataFlavor.imageFlavor.equals(flavor);
}
// Returns image
public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException {
if (!DataFlavor.imageFlavor.equals(flavor)) {
throw new UnsupportedFlavorException(flavor);
}
return image;
}
}
Exception in thread "main" java.lang.IllegalArgumentException: Width (-1) and height (-1) cannot be <= 0 at
java.awt.image.DirectColorModel.createCompatibleWritableRaster(DirectColorModel.java:999) at
sun.awt.datatransfer.DataTransferer.imageToStandardBytes(DataTransferer.java:1994) at
sun.awt.windows.WDataTransferer.imageToPlatformBytes(WDataTransferer.java:267) at
sun.awt.datatransfer.DataTransferer.translateTransferable(DataTransferer.java:1123) at
sun.awt.windows.WDataTransferer.translateTransferable(WDataTransferer.java:163) at
sun.awt.windows.WClipboard.setContentsNative(WClipboard.java:73) at
sun.awt.datatransfer.SunClipboard.setContents(SunClipboard.java:93) at
automateSignature.LoadToClipboard.main(LoadToClipboard.java:8)
I have tried to find a place in the code where width and height can be specified, but have not succeeded. I also examined the properties of the jpg file and the w and h are specified.enter code here
<resource name="cde.xml" status="updated" isCollection="false">
<mediaType>xml</mediaType>
<creator>admin</creator>
<createdTime>1352783477964</createdTime>
<lastUpdater>admin</lastUpdater>
<lastModified>1352783477964</lastModified>
<description />
<version>0</version>
<content>ZGFza2QgbGQgbGt2Zmx3ZGFzamQgYWRsa2ogYWxramRrbGEgamQK
</content>
</resource>
i want to catch nodes which are having status using xpath here is the xpath expression other part of the code is correct. I have problem with xpath expression
AXIOMXPath xpathExpression = new AXIOMXPath ( "//resourse[@name]");
I have written this piece of code to break an image into 9 pieces and it gives me runtime error. There is no error in LogCat and I am stuck. The error comes at line 7 line from bottom (Bitmap.createBitmap(...);).
public Bitmap[] getPieces(Bitmap bmp) {
Bitmap[] bmps = new Bitmap[9];
int width = bmp.getWidth();
int height = bmp.getHeight();
int rows = 3;
int cols = 3;
int cellHeight = height / rows;
int cellWidth = width / cols;
int piece = 0;
for (int x = 0; x <= width; x += cellWidth) {
for (int y = 0; y <= height; y += cellHeight) {
Bitmap b = Bitmap.createBitmap(bmp, x, y, cellWidth,
cellHeight, null, false);
bmps[piece] = b;
piece++;
}
}
return bmps;
}
i have installed open cms on my local machine and it perfectly works fine.
But in order to work it corre,ty it is mentioned that i have to modify the my.ini file and set max_alllowed_packed site to 32
I have done it and it works perfectly fine
but can i modify this file if i use a third party hosting provider for tomcat and mysql??
Recently i've found myself writing a lot of methods with what i can only think to call debugging scaffolding. Here's an example:
public static void printArray (String[] array, boolean bug)
{
for (int i = 0; i<array.lenght; i++)
{
if (bug) System.out.print (i) ; //this line is what i'm calling the debugging scaffolding i guess.
System.out.println(array[i]) ;
}
}
in this method if i set bug to true, wherever its being called from maybe by some kind of user imput, then i get the special debugging text to let me know what index the string being printed as at just in case i needed to know for the sake of my debugging (pretend a state of affairs exists where its helpful).
All of my questions more or less boil down to the question: is this a good idea? but with a tad bit more objectivity:
Is this an effective way to test my
methods and debug them? i mean effective in terms of efficiency and not messing up my code.
Is it acceptable to leave the if
(bug) stuff ; code in place after
i've got my method up and working?
(if a definition of "acceptability"
is needed to make this question
objective then use "is not a matter
of programing controversy such as
ommiting brackets in an if(boolean)
with only one line after it, though
if you've got something better go
ahead and use your definition i won't
mind)
Is there a more effective way to
accomplish the gole of making
debugging easier than what i'm doing?
Anything you know i mean to ask but
that i have forgotten too (as much
information as makes sense is
appreciated).
I am a building a console Sudoku Solver where the main objective is raw speed.
I now have a ManagerThread that starts WorkerThreads to compute the neibhbors of each cell. So one WorkerThread is started for each cell right now. How can I re-use an existing thread that has completed its work?
The Thread Pool Pattern seems to be the solution, but I don't understand what to do to prevent the thread from dying once its job has been completed.
ps : I do not expect to gain much performance for this particular task, just want to experiment how multi-threading works before applying it to the more complex parts of the code.
Thanks