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  • Java: Combine 2 List <String[]>

    - by battousai622
    I have two List of array string. I want to be able to create a New List (newList) by combining the 2 lists. But it must meet these 3 conditions: 1) Copy the contents of store_inventory into newList. 2) Then if the item names in store_inventory & new_acquisitions match, just add the two quantities together and change it in newList. 3) If new_acquisitions has a new item that does not exist in store_inventory, then add it to the newList. The titles for the CSV list are: Item Name, Quantity, Cost, Price. The List contains an string[] of item name, quantity, cost and price for each row. CSVReader from = new CSVReader(new FileReader("/test/new_acquisitions.csv")); List <String[]> acquisitions = from.readAll(); CSVReader to = new CSVReader(new FileReader("/test/store_inventory.csv")); List <String[]> inventory = to.readAll(); List <String[]> newList; Any code to get me started would be great! =] this is what i have so far... for (int i = 0; i < acquisitions.size(); i++) { temp1 = acquisitions.get(i); for (int j = 1; j < inventory.size(); j++) { temp2 = inventory.get(j); if (temp1[0].equals(temp2[0])) { //if match found... do something? //break out of loop } } //if new item found... do something? }

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  • Dijkstras Algorithm exaplination java

    - by alchemey89
    Hi, I have found an implementation for dijkstras algorithm on the internet and was wondering if someone could help me understand how the code works. Many thanks private int nr_points=0; private int[][]Cost; private int []mask; private void dijkstraTSP() { if(nr_points==0)return; //algorithm=new String("Dijkstra"); nod1=new Vector(); nod2=new Vector(); weight=new Vector(); mask=new int[nr_points]; //initialise mask with zeros (mask[x]=1 means the vertex is marked as used) for(int i=0;i<nr_points;i++)mask[i]=0; //Dijkstra: int []dd=new int[nr_points]; int []pre=new int[nr_points]; int []path=new int[nr_points+1]; int init_vert=0,pos_in_path=0,new_vert=0; //initialise the vectors for(int i=0;i<nr_points;i++) { dd[i]=Cost[init_vert][i]; pre[i]=init_vert; path[i]=-1; } pre[init_vert]=0; path[0]=init_vert; pos_in_path++; mask[init_vert]=1; for(int k=0;k<nr_points-1;k++) { //find min. cost in dd for(int j=0;j<nr_points;j++) if(dd[j]!=0 && mask[j]==0){new_vert=j; break;} for(int j=0;j<nr_points;j++) if(dd[j]<dd[new_vert] && mask[j]==0 && dd[j]!=0)new_vert=j; mask[new_vert]=1; path[pos_in_path]=new_vert; pos_in_path++; for(int j=0;j<nr_points;j++) { if(mask[j]==0) { if(dd[j]>dd[new_vert]+Cost[new_vert][j]) { dd[j]=dd[new_vert]+Cost[new_vert][j]; } } } } //Close the cycle path[nr_points]=init_vert; //Save the solution in 3 vectors (for graphical purposes) for(int i=0;i<nr_points;i++) { nod1.addElement(path[i]); nod2.addElement(path[i+1]); weight.addElement(Cost[path[i]][path[i+1]]); } }

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  • Grails or Play! for an ex-RoR developer ?

    - by Kedare
    Hello, I plan to begin learning a Java web framework (I love the Java API), I already used Rails and Django. I want something close to Java, but without all the complexity of J2EE. I've found 2 framework that could be good for me : Grails : Grails looks great, it use Groovy that is better than Java for web application (I think..), but it's slower, that use pure-java components (Hibernate, Strut, Spring), it looks pretty simple to deploy (send .war and it's ok !), the GSP is great ! It's a bit harder to debug (need to restart the server at each modification, and the stacktrace is a mix of Java and Groovy stack that is not always understandable..) Play! : This framework also looks great, it's faster than Grails (It's use directly Java), but I don't really like how it use Java, it modify the source code to transform the properties call as setXXX/getXXX, I'm not kind of that... The framework also have caching function that Grails don't (alreary) has. I don't really like the Template Engine. It's also easer to debug (no need to restart the server, and the stacktrace is clear) What do you recommend for ? I am looking for something easy to learn (I used a lot ruby and java, but a little bit java (But I love the Java API)), that is full featured (That's no a problem with all the Java Library availables, but if it's bundle and integrated I prefer), that scale and that is not too slow (faster than ruby), and if possible I would want something with a decent community to easily find support and answer to my questions ;) PS: No JRuby on Rails Thank you !

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  • Java Apache Commons users

    - by Tom Brito
    Is there anything in apache commons to convert a Object to byte array, like the following method does? public static byte[] toByteArray(Object obj) throws IOException { ByteArrayOutputStream baos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(baos); oos.writeObject(obj); oos.flush(); byte[] data = baos.toByteArray(); return data; } [try-finally block closing buffers were omitted to simplify]

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  • Control - C exception in Java

    - by Phil
    I need to catch that exception but I can't figure out which one it is. The IDE i'm using right now doesn't allow for a program interrupt that way. I know how to user try/catch, but I don't actually know what I'm trying to catch.. Can anyone help me with this?

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  • Java: JPQL select statement

    - by bguiz
    select x from X x where x.a.id = :a_id -- Always 0 objects selected Why does the above JPQL statement not work, but the one below work? select a from A a where a.id = :a_id -- a_obj select x from X x where x.a = :a_obj -- Always correct number of objects selected Neither query throws an exception during execution, but a different number of results are obtained. Thanks

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  • Passing a Java object from one Struts action to another

    - by Bernhard V
    Hello! In one of my Struts action I've got the following code in a method: ... List<Object> retrievedListOfObjects = c.getListOfObjects(); return mapping.findForward("fw_view"); } fw_view leads to a new Struts action with another Struts form. Let's say this form has got among others the following field List<Object> listOfObjects; I now want to pass the retrievedListOfObjects from within the first Struts action to the form of the following Struts action. Is this possible without storing it in the session?

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  • How to repaint a XYPlot from JFreeChart? (JAVA)

    - by mccrank
    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.

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  • Loading all files in a directory in a Java applet

    - by WarrenB
    How would one go about programatically loading all the resource files in a given directory in a JAR file for an applet? The resources will probably change several times over the lifetime of the program so I don't want to hardcode names in. Normally I would just traverse the directory structure using File.list(), but I get permission issues when trying to do that within an applet. I also looked at using an enumeration with something line ClassLoader.getResources() but it only finds files of the same name within the JAR file. Essentially what I want to do is (something like) this: ClassLoader imagesURL = this.getClass().getClassLoader(); MediaTracker tracker = new MediaTracker(this); Enumeration<URL> images = imagesURL.getResources("resources/images/image*.gif"); while (images.hasMoreElements()){ tracker.add(getImage(images.nextElement(), i); i++; } I know I'm probably missing some obvious function, but I've spent hours searching through tutorials and documentation for a simple way to do this within an unsigned applet.

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  • Arduino crashes when sending bytes from Java [on hold]

    - by francisaugusto
    I used the sample program from the arduino website in order to send and receive data via serial to my Arduino one. However, for some reason, even when I try to send only one byte, the Arduino crashes after a while. It doesn't happen if I send the chars manually via the IDE's own serial monitor. I wrote the following method to output the character to Arduino: public synchronized void serialWrite(char sendIt){ try { output.write((byte)'0'); output.flush(); for (int j=0;j<1000000000;j++){ } }catch (Exception e){System.out.println("Not connected...");} notify(); } What I try above is to send just one character when the method is called. I send just a '0' char for testing. After manually calling the method two or three times, Arduino crashes. Is there anything I should be looking into? The Arduino code: #include <SoftwareSerial.h> int buttonState=0; int lastButtonState=0; int buttonPushCounter=0; long previousMillis=0; long interval=250; int ledState=LOW; int ledState2=LOW; int ledState3=LOW; long timeElapsed=0; SoftwareSerial portOne(10,11); void setup(){ pinMode(3,OUTPUT); pinMode(4,OUTPUT); pinMode(5,OUTPUT); pinMode(2,INPUT); Serial.begin(9600); portOne.begin(9600); } boolean turnoff; void loop(){ if(portOne.overflow()){ Serial.println("There's an overflow here!"); } buttonState= digitalRead(2); if(buttonState!=lastButtonState){ if (buttonState==HIGH){ buttonPushCounter++; } } lastButtonState=buttonState; if (turnoff){ unsigned long currentMillis=millis(); if (currentMillis-previousMillis>0 && currentMillis-previousMillis<interval){ ledState=HIGH; ledState2=LOW; ledState3=LOW; }else if (currentMillis-previousMillis>interval && currentMillis-previousMillis<interval*2){ ledState=LOW; ledState2=LOW; ledState3=HIGH; }else if (currentMillis-previousMillis>interval*2 && currentMillis-previousMillis<interval*3){ ledState=LOW; ledState2=HIGH; ledState3=LOW; }else if (currentMillis-previousMillis>interval*3){ previousMillis=currentMillis; } digitalWrite(3,ledState); digitalWrite(4,ledState2); digitalWrite(5,ledState3); }else{ digitalWrite(3,LOW); digitalWrite(4,LOW); digitalWrite(5,LOW); } if (buttonPushCounter==1){ Serial.print("Button pressed!\n"); turnoff=!turnoff; buttonPushCounter=0; } noInterrupts(); char ch=Serial.read(); delay(1); if(ch=='0'){ Serial.println("Changed by serial"+turnoff); Serial.println(ch); turnoff=!turnoff; } interrupts(); }

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  • parallel computation for an Iterator of elements in Java

    - by Brian Harris
    I've had the same need a few times now and wanted to get other thoughts on the right way to structure a solution. The need is to perform some operation on many elements on many threads without needing to have all elements in memory at once, just the ones under computation. As in, Iterables.partition is insufficient because it brings all elements into memory up front. Expressing it in code, I want to write a BulkCalc2 that does the same thing as BulkCalc1, just in parallel. Below is sample code that illustrates my best attempt. I'm not satisfied because it's big and ugly, but it does seem to accomplish my goals of keeping threads highly utilized until the work is done, propagating any exceptions during computation, and not having more than numThreads instances of BigThing necessarily in memory at once. I'll accept the answer which meets the stated goals in the most concise way, whether it's a way to improve my BulkCalc2 or a completely different solution. interface BigThing { int getId(); String getString(); } class Calc { // somewhat expensive computation double calc(BigThing bigThing) { Random r = new Random(bigThing.getString().hashCode()); double d = 0; for (int i = 0; i < 100000; i++) { d += r.nextDouble(); } return d; } } class BulkCalc1 { final Calc calc; public BulkCalc1(Calc calc) { this.calc = calc; } public TreeMap<Integer, Double> calc(Iterator<BigThing> in) { TreeMap<Integer, Double> results = Maps.newTreeMap(); while (in.hasNext()) { BigThing o = in.next(); results.put(o.getId(), calc.calc(o)); } return results; } } class SafeIterator<T> { final Iterator<T> in; SafeIterator(Iterator<T> in) { this.in = in; } synchronized T nextOrNull() { if (in.hasNext()) { return in.next(); } return null; } } class BulkCalc2 { final Calc calc; final int numThreads; public BulkCalc2(Calc calc, int numThreads) { this.calc = calc; this.numThreads = numThreads; } public TreeMap<Integer, Double> calc(Iterator<BigThing> in) { ExecutorService e = Executors.newFixedThreadPool(numThreads); List<Future<?>> futures = Lists.newLinkedList(); final Map<Integer, Double> results = new MapMaker().concurrencyLevel(numThreads).makeMap(); final SafeIterator<BigThing> it = new SafeIterator<BigThing>(in); for (int i = 0; i < numThreads; i++) { futures.add(e.submit(new Runnable() { @Override public void run() { while (true) { BigThing o = it.nextOrNull(); if (o == null) { return; } results.put(o.getId(), calc.calc(o)); } } })); } e.shutdown(); for (Future<?> future : futures) { try { future.get(); } catch (InterruptedException ex) { // swallowing is OK } catch (ExecutionException ex) { throw Throwables.propagate(ex.getCause()); } } return new TreeMap<Integer, Double>(results); } }

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  • Java For-Each Loop to Deal to multiple Hands

    - by qwertyRocker
    I'm trying to find a good way to 'deal' cards to 4 difference hands. System.out.println("Deal to 4 Hands: "); Hand hand1 = new Hand(); Hand hand2 = new Hand(); Hand hand3 = new Hand(); Hand hand4 = new Hand(); hand1.addSingleCard(Deck.deal()); hand2.addSingleCard(Deck.deal()); hand3.addSingleCard(Deck.deal()); hand4.addSingleCard(Deck.deal()); hand1.addSingleCard(Deck.deal()); hand2.addSingleCard(Deck.deal()); hand3.addSingleCard(Deck.deal()); hand4.addSingleCard(Deck.deal()); System.out.println("Cards left in deck: " + Deck.size()); System.out.println("Player 1's Hand: \n" + hand1.getHand()); System.out.println("Player 2's Hand: \n" + hand2.getHand()); System.out.println("Player 3's Hand: \n" + hand3.getHand()); System.out.println("Player 4's Hand: \n" + hand4.getHand()); Is there an easier way to deal to hands? For example using a For-Each loop? I tried this: but it doesn't work. I haven't really used this type of loop very must... for(Hand card : hand1){ System.out.println("Player 1's Hand: \n" + hand1); } By the way, this deals 2 cards to 4 difference hands, then prints each hand.

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  • How to sort Map in Java

    - by kalpesh
    hi i want to sort map according to its key value plz see code below public static void main(String[] args) { SortedMap map = new TreeMap(); // Add some elements: map.put("2", "Two"); map.put("1", "One"); map.put("5", "Five"); map.put("4", "Four"); map.put("3", "Three"); map.put("10", "Ten"); map.put("12", "Twelve"); map.put("7", "Seven"); map.put("9", "Nine"); Iterator iterator = map.keySet().iterator(); while (iterator.hasNext()) { Object key = iterator.next(); System.out.println("key : " + key + " value :" + map.get(key)); } } Result Should come below key : 1 value :One key : 2 value :Two key : 3 value :Three key : 4 value :Four key : 5 value :Five key : 7 value :Seven key : 9 value :Nine key : 10 value :Ten key : 12 value :Twelve

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  • Java - Collections.sort() performance

    - by msr
    Hello, Im using Collections.sort() to sort a LinkedList whose elements implements Comparable interface, so they are sorted in a natural order. In the javadoc documentation its said this method uses mergesort algorithm wich has n*log(n) performance. My question is if there is a more efficient algorithm to sort my LinkedList? The size of that list could be very high and sort will be also very frequent. Thanks!

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  • How do I dynamically name objects in Java?

    - by hatboysam
    Let's say I needed to make a series of String[] objects. I know that if i wanted to make a string array called "test" to hold 3 Strings I could do String[] test = new String[3]; But let's say I needed to make a series of these arrays and I wanted them to be named, 1,2, 3, 4, 5... etc. For however many I needed and I didn't know how many I'd need. How do I achieve a similar effect to this: for (int k=0; k=5; k++){ String[] k = new String[3]; } Which would created 5 string arrays named 1 through 5. Basically I want to be able to create array objects with a name detemined by some other function. Why can't I seem to do this? Am I just being stupid?

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  • Static and overriding in Java

    - by Abhishek Jain
    public class B { static int i =1; public static int multiply(int a,int b) { return i; } public int multiply1(int a,int b) { return i; } public static void main(String args[]) { B b = new A(); System.out.println(b.multiply(5,2)); System.out.println(b.multiply1(5,2)); } } class A extends B { static int i =8; public static int multiply(int a,int b) { return 5*i; } public int multiply1(int a,int b) { return 5*i; } } Output: 1 40 Why is it so? Please explain.

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  • J2ME/Java: Referencing StringBuffer through Threads

    - by Jemuel Dalino
    This question might be long, but I want to provide much information. Overview: I'm creating a Stock Quotes Ticker app for Blackberry. But I'm having problems with my StringBuffer that contains an individual Stock information. Process: My app connects to our server via SocketConnection. The server sends out a formatted set of strings that contains the latest Stock trade. So whenever a new trade happens, the server will send out an individual Stock Quote of that trade. Through an InputStream I am able to read that information and place each character in a StringBuffer that is referenced by Threads. By parsing based on char3 I am able to determine a set of stock quote/information. char1 - to separate data char3 - means end of a stock quote/information sample stock quote format sent out by our server: stock_quote_name(char 1)some_data(char1)some_data(char1)(char3) My app then parses that stock quote to compare certain data and formats it how it will look like when displayed in the screen. When trades happen gradually(slow) the app works perfectly. However.. Problem: When trades happen too quickly and almost at the same time, My app is not able to handle the information sent efficiently. The StringBuffer has its contents combined with the next trade. Meaning Two stock information in one StringBuffer. field should be: Stock_quote_name some_data some_data sample of what's happening: Stock_quote_name some_data some_dataStock_quote_name some_data some_data here's my code for this part: while (-1 != (data = is.read())) { sb.append((char)data); while(3 != (data = is.read())) { sb.append((char)data); } UiApplication.getUiApplication().invokeLater(new Runnable() { public void run() { try { synchronized(UiApplication.getEventLock()) { SetStringBuffer(sb); DisplayStringBuffer(); RefreshStringBuffer(); } } catch (Exception e) { System.out.println("Error in setting stringbuffer: " + e.toString()); } } }); } public synchronized void DisplayStringBuffer() { try { //parse sb - string buffer ...... } catch(Exception ex) { System.out.println("error in DisplayStringBuffer(): " + ex.toString()); } } public synchronized void SetStringBuffer(StringBuffer dataBuffer) { this.sb =dataBuffer; System.out.println(sb); } public synchronized void RefreshStringBuffer() { this.sb.delete(0, this.sb.length()); } From what I can see, when trades happen very fast, The StringBuffer is not refreshed immediately and still has the contents of the previous trade, when i try to put new data. My Question is: Do you guys have any suggestion on how i can put data into the StringBuffer, without the next information being appended to the first content

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  • Java regex basic usage problem

    - by Ernelli
    The following code works: String str= "test with foo hoo"; Pattern pattern = Pattern.compile("foo"); Matcher matcher = pattern.matcher(str); if(matcher.find()) { ... } But this example does not: if(Pattern.matches("foo", str)) { ... } And neither this version: if(str.matches("foo")) { ... } In the real code, str is a chunk of text with multiple lines if that is treated differently by the matcher, also in the real code, replace will be used to replace a string of text. Anyway, it is strange that it works in the first version but not the other two versions.

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