If given subnet address e.g. 192.168.10.0/24
How to determine mask length ? (/24)
How to determine mask address ? (255.255.255.0)
How to determine network address ? (192.168.10.0)
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?
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
I am maintaining this servlet that has a HttpServletResponse response that replies back to the client an XML message. I want to take the XML message and convert it to JSON, then send the JSON back.
I want to avoid writing my own JSON converter if possible. Does anyone have a good method of doing this?
I googled for this: http://pvoss.wordpress.com/2009/02/26/servlet-filter-to-convert-xml-to-json/ , which is exactly what I want but they are using a hacked dom4j jar which doesn't help me.
Suppose I have a string that contains '¿'. How would I find all those unicode characters? Should I test for their code? How would I do that?
I want to detect it to avoid sax parser exception which I am getting it while parsing the xml
saved as a clob in oracle 10g database.
Exception
javax.servlet.ServletException: org.xml.sax.SAXParseException: Invalid byte 1 of 1-byte UTF-8 sequence.
Say I have two threads and an object. One thread assigns the object:
public void assign(MyObject o) {
myObject = o;
}
Another thread uses the object:
public void use() {
myObject.use();
}
Does the variable myObject have to be declared as volatile? I am trying to understand when to use volatile and when not, and this is puzzling me. Is it possible that the second thread keeps a reference to an old object in its local memory cache? If not, why not?
Thanks a lot.
I know there are LOT of questions like that but I can't find one specific to my situation. I have 4x4 matrices implemented as NIO float buffers (These matrices are used for OpenGL). Now I want to implement a multiply method which multiplies Matrix A with Matrix B and stores the result in Matrix C. So the code may look like this:
class Matrix4f
{
private FloatBuffer buffer = FloatBuffer.allocate(16);
public Matrix4f multiply(Matrix4f matrix2, Matrix4f result)
{
{{{result = this * matrix2}}} <-- I need this code
return result;
}
}
What is the fastest possible code to do this multiplication? Some OpenGL implementations (Like the OpenGL ES stuff in Android) provide native code for this but others doesn't. So I want to provide a generic multiplication method for these implementations.
hi,
first time dealing with xml, so please be patient. the code below is probably evil in a million ways (I'd be very happy to hear about all of them), but the main problem is of course that it doesn't work :-)
public class Test {
private static final String JSDL_SCHEMA_URL = "http://schemas.ggf.org/jsdl/2005/11/jsdl";
private static final String JSDL_POSIX_APPLICATION_SCHEMA_URL = "http://schemas.ggf.org/jsdl/2005/11/jsdl-posix";
public static void main(String[] args) {
System.out.println(Test.createJSDLDescription("/bin/echo", "hello world"));
}
private static String createJSDLDescription(String execName, String args) {
Document jsdlJobDefinitionDocument = getJSDLJobDefinitionDocument();
String xmlString = null;
// create the elements
Element jobDescription = jsdlJobDefinitionDocument.createElement("JobDescription");
Element application = jsdlJobDefinitionDocument.createElement("Application");
Element posixApplication = jsdlJobDefinitionDocument.createElementNS(JSDL_POSIX_APPLICATION_SCHEMA_URL, "POSIXApplication");
Element executable = jsdlJobDefinitionDocument.createElement("Executable");
executable.setTextContent(execName);
Element argument = jsdlJobDefinitionDocument.createElement("Argument");
argument.setTextContent(args);
//join them into a tree
posixApplication.appendChild(executable);
posixApplication.appendChild(argument);
application.appendChild(posixApplication);
jobDescription.appendChild(application);
jsdlJobDefinitionDocument.getDocumentElement().appendChild(jobDescription);
DOMSource source = new DOMSource(jsdlJobDefinitionDocument);
validateXML(source);
try {
Transformer transformer = TransformerFactory.newInstance().newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
StreamResult result = new StreamResult(new StringWriter());
transformer.transform(source, result);
xmlString = result.getWriter().toString();
} catch (Exception e) {
e.printStackTrace();
}
return xmlString;
}
private static Document getJSDLJobDefinitionDocument() {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = null;
try {
builder = factory.newDocumentBuilder();
} catch (Exception e) {
e.printStackTrace();
}
DOMImplementation domImpl = builder.getDOMImplementation();
Document theDocument = domImpl.createDocument(JSDL_SCHEMA_URL, "JobDefinition", null);
return theDocument;
}
private static void validateXML(DOMSource source) {
try {
URL schemaFile = new URL(JSDL_SCHEMA_URL);
Sche maFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
Schema schema = schemaFactory.newSchema(schemaFile);
Validator validator = schema.newValidator();
DOMResult result = new DOMResult();
validator.validate(source, result);
System.out.println("is valid");
} catch (Exception e) {
e.printStackTrace();
}
}
}
it spits out a somewhat odd message:
org.xml.sax.SAXParseException: cvc-complex-type.2.4.a: Invalid content was found starting with element 'JobDescription'. One of '{"http://schemas.ggf.org/jsdl/2005/11/jsdl":JobDescription}' is expected.
Where am I going wrong here?
Thanks a lot
Lets say that I have the following code:
public class Shelter<A extends Animal, B extends Animal>
{
List<A> topFloor = new Vector<A>();
List<B> bottomFloor = new Vector<B>();
public A getFirstTopFloorAnimal(){return topFloor.firstElement();}
public B getFirstBottomFloorAnimal(){return bottomFloor.firstElement();}
//This compiles but when I try to use it, it only returns objects
public List<Animal> getAnimals()
{
Vector a = new Vector(topFloor);
a.addAll(bottomFloor);
return a;
}
}
Now for somereason the following code compiles. But when I try to use getAnimals() I get a of objects instead of Animal. Any ideas why this is? Does this have to do with the List is NOT a List idea in the Generics tutorial?
Thank you.
I have a large distributed program across many different physical servers, each program spawns many threads, each thread use Math.random() in its operations to draw a piece from many common resource pools.
The goal is to utilize the pools evenly across all operations. Sometimes, it doesn't appear so random by looking at a snapshot on a resource pool to see which pieces it's getting at that instant (it might actually be, but it's hard to measure and find out for sure).
Is there something that's better than Math.random() and performs just as good (not much worse at least)?
I started down this path of implementing a simple search in an array for a hw assignment without knowing we could use ArrayList. I realized it had some bugs in it and figured I'd still try to know what my bug is before using ArrayList. I basically have a class where I can add, remove, or search from an array.
public class AcmeLoanManager
{
public void addLoan(Loan h)
{
int loanId = h.getLoanId();
loanArray[loanId - 1] = h;
}
public Loan[] getAllLoans()
{
return loanArray;
}
public Loan[] findLoans(Person p)
{
//Loan[] searchedLoanArray = new Loan[10]; // create new array to hold searched values
searchedLoanArray = this.getAllLoans(); // fill new array with all values
// Looks through only valid array values, and if Person p does not match using Person.equals()
// sets that value to null.
for (int i = 0; i < searchedLoanArray.length; i++) {
if (searchedLoanArray[i] != null) {
if (!(searchedLoanArray[i].getClient().equals(p))) {
searchedLoanArray[i] = null;
}
}
}
return searchedLoanArray;
}
public void removeLoan(int loanId)
{
loanArray[loanId - 1] = null;
}
private Loan[] loanArray = new Loan[10];
private Loan[] searchedLoanArray = new Loan[10]; // separate array to hold values returned from search
}
When testing this, I thought it worked, but I think I am overwriting my member variable after I do a search. I initially thought that I could create a new Loan[] in the method and return that, but that didn't seem to work. Then I thought I could have two arrays. One that would not change, and the other just for the searched values. But I think I am not understanding something, like shallow vs deep copying???....
class A extends ApiClass
{
public void duplicateMethod()
{
}
}
class B extends AnotherApiClass
{
public void duplicateMethod()
{
}
}
I have two classes which extend different api classes. The two class has some duplicate
methods(same method repeated in both class) and how to remove this duplication?
Edit
The ApiClass is not under my control
This is what I want to do:
Input: ArrayList that contains a bunch of .jpg URLs
Download the image (using HttpURLConnection maybe?)
Resize
Save as xxx.jpg, locally
I don't know where to start. I'd appreciate if anyone can tell me what to study to do the steps 1~3.
I can understand why network apps would use multiplexing (to not create too many threads), and why programs would use async calls for pipelining (more efficient). But I don't understand the purpose of AsynchronousFileChannel.
Any ideas?
I'm trying to make a program that uploads a image to a webserver that accepts multipart file-uploads.
More specificly i want to make a http POST request to http://iqs.me that sends a file in the variable "pic".
I've made a lot of tries but i don't know if i've even been close. The hardest part seems to be to get a HttpURLConnection to make a request of the type POST. The response i get looks like it makes a GET.
(And i want to do this without any third party libs)
UPDATE: non-working code goes here (no errors but doesn't seem to do a POST):
HttpURLConnection conn = null;
BufferedReader br = null;
DataOutputStream dos = null;
DataInputStream inStream = null;
InputStream is = null;
OutputStream os = null;
boolean ret = false;
String StrMessage = "";
String exsistingFileName = "myScreenShot.png";
String lineEnd = "\r\n";
String twoHyphens = "--";
String boundary = "*****";
int bytesRead, bytesAvailable, bufferSize;
byte[] buffer;
int maxBufferSize = 1*1024*1024;
String responseFromServer = "";
String urlString = "http://iqs.local.com/index.php";
try{
FileInputStream fileInputStream = new FileInputStream( new File(exsistingFileName) );
URL url = new URL(urlString);
conn = (HttpURLConnection) url.openConnection();
conn.setDoInput(true);
conn.setDoOutput(true);
conn.setRequestMethod("POST");
conn.setUseCaches(false);
conn.setRequestProperty("Connection", "Keep-Alive");
conn.setRequestProperty("Content-Type", "multipart/form-data;boundary="+boundary);
dos = new DataOutputStream( conn.getOutputStream() );
dos.writeBytes(twoHyphens + boundary + lineEnd);
dos.writeBytes("Content-Disposition: form-data; name=\"pic\";" + " filename=\"" + exsistingFileName +"\"" + lineEnd);
dos.writeBytes(lineEnd);
bytesAvailable = fileInputStream.available();
bufferSize = Math.min(bytesAvailable, maxBufferSize);
buffer = new byte[bufferSize];
bytesRead = fileInputStream.read(buffer, 0, bufferSize);
while (bytesRead > 0){
dos.write(buffer, 0, bufferSize);
bytesAvailable = fileInputStream.available();
bufferSize = Math.min(bytesAvailable, maxBufferSize);
bytesRead = fileInputStream.read(buffer, 0, bufferSize);
}
dos.writeBytes(lineEnd);
dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);
fileInputStream.close();
dos.flush();
dos.close();
}catch (MalformedURLException ex){
System.out.println("Error:"+ex);
}catch (IOException ioe){
System.out.println("Error:"+ioe);
}
try{
inStream = new DataInputStream ( conn.getInputStream() );
String str;
while (( str = inStream.readLine()) != null){
System.out.println(str);
}
inStream.close();
}catch (IOException ioex){
System.out.println("Error: "+ioex);
}
Hi,
I'm doing a GUI that has a XYPlot (from the JFreeChart package) and when I click a button I'm trying to add some values. I add them correctly to the XYSeries that are inside the XYPlot, but the GUI doesn't change. It only changes when y maximize or minimize. Is there some kind of repaint to do this? I have been looking for it and I have found nothing.
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).
Suppose I have a big program that consists of hundreds of methods in it. And according to the nature of input the program flow is getting changed.
Think I want to make a change to the original flow. And it is big hassle to find call hierarchy/ references and understand the flow.
Do I have any solution for this within Eclipse? Or a plugin? As an example, I just need a Log of method names that is in order of time. Then I don't need to worry about the methods that are not relevant with my "given input"
Update : Using debug mode in eclipse or adding print messages are not feasible. The program is sooooo big. :)
I read http://stackoverflow.com/questions/839178/why-is-javas-iterator-not-an-iterable and http://stackoverflow.com/questions/27240/why-arent-enumerations-iterable, but I still don't understand why this:
void foo(Iterator<X> it) {
for (X x : it) {
bar(x);
baz(x);
}
}
was not made possible. In other words, unless I'm missing something, the above could have been nice and valid syntactic sugar for:
void foo(Iterator<X> it) {
for (X x; it.hasNext();) {
x = it.next();
bar(x);
baz(x);
}
}
Hi guys,
if I have the following private member:
private int xIndex;
How should I name my gettter/setter:
getXindex()
setXindex(int value)
or
getxIndex()
setxIndex(int value)
Hi, I'd like to know if it is possible to make a progress bar displayed on the taskbar like Windows Explorer does when there's a file operation going on? I saw many examples, but they all involved C#.
SWT won't cut it.
I recently attended a talk by a Sun engineer Charlie Hunt regarding performance. The talk was interesting enough but one question was regarding release date of 1.7.
He said it's delayed as there are parties who are refusing to sign off JSRs they own and thus preventing the 1.7 release. It apparently has something to do with the cost of determining your Sun compliance.
I would be interested to know the full story if anyone knows or can point me in the right direction.
What triggered my question was the amazing long release notes for 6u18.
Thanks
How should I go about implementing a method that gets a String composed of Latin characters to translate it into a String composed of a different set of characters, let's say Cyrillic.