We always say that method overloading is static polymorphism and overriding is runtime polymorphism. What exactly do we mean by static here? Is the call to a method resolved on compiling the code? So whats the difference between normal method call and calling a final method? Which one is linked at compile time?
Hello,
I'm not able to understand the following multi-dimensional code. Could someone please clarify me?
int[][] myJaggedArr = new int [][]
{
new int[] {1,3,5,7,9},
new int[] {0,2,4,6},
new int[] {11,22}
};
May I know how it is different from the following code?
int[][] myArr = new int [][] {
{1,3,5,7,9},
{0,2,4,6},
{11,22} };
I've set up a simple Eclipse 3.5/Jetty 6.1 web app which returns hello world. It works. This is on Windows and uses the "Jetty Generic Server Adapter". I have auto deployment working so that it deploys after changes periodically.
How do I go about setting it up so that if I change any static content it doesn't have to redeploy i.e I can just hit F5 to see the changes straight away. For minor HTML changes it's quite unusable waiting 20-30 seconds for a deployment.
If I use a statement in my code like
int[] a = new int[42];
does it initialized the array to anything in particular? (e.g. 0) I seem to remember this is documented somewhere but I am not sure what to search for.
There´s any eclipse shortcut to stance a new object ?
For example. I would like to type:
Object zzz =
and it would complete for me this way:
Object zzz = new Object();
with void parameter of course.
I will wait answers.. thank you people.
I have 1 thread who sole job is to grab DatagramPackets off of a socket and stick them in a buffer. Another thread works out of that buffer, processing the DatagramPackets. I'd like to have a pool of threads working out of that buffer.
I had thought to use a fixed thread pool to do this. To do so, do I need to create the pool, then submit enough runnables for execution to fill it up? I had hoped for a way to say "this is the thread/runnable that I want you to execute, this is how many I want running, GO!". Is there such a method of doing this? Is something other than a fixed thread pool better suited?
I've come across Netbeans but is there any tools out there that lets you build things event driven ?
I'm looking for a feature like being able to drag and drop UI components, and add methods to buttons directly by double clicking it (kinda like visualbasic) and viewing the source.
I've a typical scenario & need to understand best possible way to handle this, so here it goes -
I'm developing a solution that will retrieve data from a remote SOAP based web service & will then push this data to an Oracle database on network.
Also, this will be a scheduled task that will execute every 15 minutes.
I've event queues on remote service that contains the INSERT/UPDATE/DELETE operations that have been done since last retrieval, & once I retrieve the events for last 15 minutes, it again add events for next retrieval.
Now, its just pushing data to Oracle so all my interactions are INSERT & UPDATE statements.
There are around 60 tables on Oracle with some of them having 100+ columns. Moreover, for every 15 minutes cycle there would be around 60-70 Inserts, 100+ Updates & 10-20 Deletes.
This will be an executable jar file that will terminate after operation & will again start on next 15 minutes cycle.
So, I need to understand how should I handle WRITE operations (best practices) to improve performance for this application as whole ?
Current Test Code (on every cycle) -
Connects to remote service to get events.
Creates a connection with DB (single connection object).
Identifies the type of operation (INSERT/UPDATE/DELETE) & table on which it is done.
After above, calls the respective method based on type of operation & table.
Uses Preparedstatement with positional parameters, & retrieves each column value from remote service & assigns that to statement parameters.
Commits the statement & returns to get event class to process next event.
Above is repeated till all the retrieved events are processed after which program closes & then starts on next cycle & everything repeats again.
Thanks for help !
I'm maintaining this Swing app that has a "print" option. Users need to be kept from interacting in any way with the underlying file system, but the print dialog offers "print to file" as one printer, and that of course allows selecting a directory and file from the file system.
Is there a painless way to override/modify the print dialog to hide the "to file" printer from this dialog? I understand the API will let me do this piecemeal but I'd rather not have to re-create most of the dialog GUI and functionality to do this.
I'm using SAX and XML reader to read XML weather info from the web and it works fine if the page exists. But if for instance the user inputs an invalid city, zip etc the XML page that gets read from is empty and the app force closes with nullpointerexception. The area that generates the error is here right at open inputstream. Any suggestions?:
SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser sp = null;
try {
sp = spf.newSAXParser();
} catch (ParserConfigurationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SAXException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
/* Get the XMLReader of the SAXParser we created. */
XMLReader xr = null;
try {
xr = sp.getXMLReader();
} catch (SAXException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
/* Create a new ContentHandler and apply it to the XML-Reader*/
WeatherHandler myExampleHandler = new WeatherHandler();
xr.setContentHandler(myExampleHandler);
/* Parse the xml-data from our URL. */
try {
xr.parse(new InputSource(url.openStream()));
parsedWeatherDataSet =
myExampleHandler.getParsedData();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SAXException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return parsedWeatherDataSet.toString();
I saw a lot of post on StackOverflow relating to this, but unable to solve my problem.
I want to open a new Panel by clicking a button.
Here is how i try to do it
parameterButton = new JButton("Parametres");
parameterButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
createParameterPanel = new DisplayParameterPanel();
createParameterPanel.setVisible(true);
add(createParameterPanel);
};
});
add(parameterButton);
When I click the parameterButton it doesn't open.
How can I open a new panel.
Thanks,
I've been working on this for one hour, just can't get it.
I have a Vector2d class:
public class Vector2d
{
public double x = 0.0;
public double y = 0.0;
....
}
This vector class has a rotate() method which is causing me trouble.
The first snippet seems to make the x and y values smaller and smaller. The second one works just fine! Am I missing something simple here?
public void rotate(double n)
{
this.x = (this.x * Math.cos(n)) - (this.y * Math.sin(n));
this.y = (this.x * Math.sin(n)) + (this.y * Math.cos(n));
}
This works:
public void rotate(double n)
{
rx = (this.x * Math.cos(n)) - (this.y * Math.sin(n));
ry = (this.x * Math.sin(n)) + (this.y * Math.cos(n));
x = rx;
y = ry;
}
I just can't spot any difference there
This is NOT a question about which is the best framework, etc.
I have never used a mocking framework and I'm a bit puzzled by the idea. How does it know how to create the mock object? Is it done in runtime or generates a file? How do you know its behavior? And most importantly - what is the work flow of using such a framework (what is the step-by-step for creating a test).
Can anyone explain? You can choose whichever framework you like for example, just say what it is.
the Method hasTwoTrueValues returns true if at least two values in an array of booleans are true. Provide the Big-Oh running time for all three implementations proposed.
// Version 1
public boolean has TwoTrueValues( boolean [ ] arr ) {
int count = 0;
for( int i = 0; i < arr. length; i++ )
if( arr[ i ] )
count++;
return count >= 2;
}
// Version 2
public boolean hasTwoTrueValues( boolean [ ] arr ) {
for( int i = 0; i < arr.length; i++ )
for( int j = i + 1; j < arr.length; j++ )
if( arr[ i ] && arr[ j ] )
return true;
}
// Version 3
public boolean hasTwoTrueValues( boolean [ ] arr ) {
for( int i = 0; i < arr.length; i++
if( arr[ i ] )
for( int j = i + 1; j < arr.length; j++ )
if( arr[ j ] )
return true;
return false;
}
For Version 1 I say the running time is O(n)
Version 2 I say O(n^2)
Version 3 I say O(n^2)
I am really new to this Big Oh Notation so if my answers are incorrect could you please explain and help.
Hi I am creating a method that will take a number and print it along with its binary representation. The problems is that my method prints all 0's for any positive number, and all 1's for any negative number
private static void display( int number ){
System.out.print(number + "\t");
int mask = 1 << 31;
for(int i=1; i<=32; i++) {
if( (mask & number) != 0 )
System.out.print(1);
else
System.out.print(0);
if( (i % 4) == 0 )
System.out.print(" ");
}
}
Simple question, but tricky answer I guess.
Does using Generic Interfaces hurts performance?
Example:
public interface Stuff<T> {
void hello(T var);
}
vs
public interface Stuff {
void hello(Integer var); <---- Integer used just as an example
}
My first thought is that it doesn't. Generics are just part of the language and the compiler will optimize it as though there were no generics (at least in this particular case of generic interfaces).
Is this correct?
Is a variable inside the main, a public variable?
public static void main(String[] args) {
.........
for(int i=0;i<threads.length;i++)
try {
threads[i].join();
} catch (InterruptedException e) {
e.printStackTrace();
}
long time=0;
....
}
i and time are they both public variables?
Of course if my reasoning is correct, also any variable belonging to a public method should be considered public.. am i right?
Thanks
I have a servlet that receives some POST data. Because this data is x-www-form-urlencoded, a string such as ???? would be encoded to サボテン.
How would I unencode this string back to the correct characters? I have tried using URLDecoder.decode("encoded string", "UTF-8"); but it doesn't make a difference.
The reason I would like to unencode them, is because, before I display this data on a webpage, I escape & to & and at the moment, it is escaping the &s in the encoded string so the characters are not showing up properly.
Hi, I have a string like this String str = "la$le\$li$lo".
I want to split it to get the following output "la","le\$li","lo". The \$ is a $ escaped so it should be left in the output.
But when I do str.split("[^\\\\]\\$") y get "l","le\$l","lo".
From what I get my regex is matching a$ and i$ and removing then. Any idea of how to get my characters back?
Thanks
I use setLayout (null) and I'm trying to place the buttons and textfield places I know by x, y
The problem when I run the program no matter what software (Eclipse, bluej)
I need to run on the panel with the mouse until I stand on the position of the button and I can see it.
When I find the textfield, it is small and only when I start writing it became the size I set it
Does anyone know how to solve it?
Hi
I have a method that has a reference to a linked list and a int value. So, this method would count and return how often the value happens in the linked list. So, I decided to make a class,
public class ListNode{
public ListNode (int v, ListNode n) {value = v; next = n;)
public int value;
public ListNode next;
}
Then, the method would start with a
public static int findValue(ListNode x, int valueToCount){
// so would I do it like this?? I don't know how to find the value,
// like do I check it?
for (int i =0; i< x.length ;i++){
valueToCount += valueToCount;
}
So, I CHANGED this part, If I did this recursively, then I would have
public static int findValue(ListNode x, int valueToCount) {
if (x.next != null && x.value == valueToCount {
return 1 + findValue(x, valueToCount);}
else
return new findvalue(x, valueToCount);
SO, is the recursive part correct now?
Write a recursive method that converts a decimal number into a binary number as a string. The method header is as follows:
public static String convertDecimalToBinary(int value)