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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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  • 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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  • 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 HTTP Request Occasionally Hangs

    - by behrk2
    Hello Everyone, For the majority of the time, my HTTP Requests work with no problem. However, occasionally they will hang. The code that I am using is set up so that if the request succeeds (with a response code of 200 or 201), then call screen.requestSucceeded(). If the request fails, then call screen.requestFailed(). When the request hangs, however, it does so before one of the above methods are called. Is there something wrong with my code? Should I be using some sort of best practice to prevent any hanging? The following is my code. I would appreciate any help. Thanks! HttpConnection connection = (HttpConnection) Connector.open(url + connectionParameters); connection.setRequestMethod(method); connection.setRequestProperty("WWW-Authenticate", "OAuth realm=api.netflix.com"); if (method.equals("POST")) { connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded"); } int responseCode = connection.getResponseCode(); System.out.println("RESPONSE CODE: " + responseCode); if (connection instanceof HttpsConnection) { HttpsConnection secureConnection = (HttpsConnection) connection; String issuer = secureConnection.getSecurityInfo() .getServerCertificate().getIssuer(); UiApplication.getUiApplication().invokeLater( new DialogRunner( "Secure Connection! Certificate issued by: " + issuer)); } if (responseCode != 200 && responseCode != 201) { screen.requestFailed("Unexpected response code: " + responseCode); connection.close(); return; } String contentType = connection.getHeaderField("Content-type"); ByteArrayOutputStream baos = new ByteArrayOutputStream(); InputStream responseData = connection.openInputStream(); byte[] buffer = new byte[20000]; int bytesRead = 0; while ((bytesRead = responseData.read(buffer)) > 0) { baos.write(buffer, 0, bytesRead); } baos.close(); connection.close(); screen.requestSucceeded(baos.toByteArray(), contentType); } catch (IOException ex) { screen.requestFailed(ex.toString()); }

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  • How to set more panels in Java

    - by baklap
    I need to get two JPanels into one JApplet. paneel = new RekenmachinePaneel(); nummer = new NummerPaneel(); setContentPane(paneel); Now I need to get the nummer panel to show up beneath the paneel. How should I do that?

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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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  • java.util.concurrent.ThreadPoolExecutor strange logic

    - by rodrigoap
    Look ath this method of ThreadPoolExcecutor: public void execute(Runnable command) { ... if (runState == RUNNING && workQueue.offer(command)) { if (runState != RUNNING || poolSize == 0) ensureQueuedTaskHandled(command); } ... } It check that runState is RUNNING and then the oposite. As I'm trying to do some tuning on a SEDA like model I wanted to understand the internals of the thread pool. Do you think this code is correct?

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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 Convert ColorSpace of BufferedImage to CS_GRAY without using ConvertColorOp

    - by gmatt
    I know its possible to convert an image to CS_GRAY using public static BufferedImage getGrayBufferedImage(BufferedImage image) { BufferedImageOp op = new ColorConvertOp(ColorSpace .getInstance(ColorSpace.CS_GRAY), null); BufferedImage sourceImgGray = op.filter(image, null); return sourceImgGray; } however, this is a chokepoint of my entire program. I need to do this often, on 800x600 pixel images and takes about 200-300ms for this operation to complete, on average. I know I can do this alot faster by using one for loop to loop through the image data and set it right away. The code above on the other hand constructs a brand new 800x600 BufferedImage that is gray scale. I would rather just transform the image I pass in. Does any one know how to do this with a for loop and given that the image is RGB color space?

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  • Java multi Generic collection parameters complie error

    - by Geln Yang
    Hi, So strange!Please have a look the code first: public class A { } public class B extends A { } public class C extends A { } public class TestMain { public <T extends A> void test(T a, T b) { } public <T extends A> void test(List<T> a, List<T> b) { } public static void main(String[] args) { new TestMain().test(new B(), new C()); new TestMain().test(new ArrayList<B>(), new ArrayList<C>()); } } The statement "new TestMain().test(new ArrayList(), new ArrayList())" get a "Bound mismatch" compile error, while "new TestMain().test(new B(), new C())" is compiled ok. Bound mismatch: The generic method test(T, T) of type TestMain is not applicable for the arguments (ArrayList, ArrayList). The inferred type ArrayList is not a valid substitute for the bounded parameter It seems the type of the second generic List parameter is limited by the Type of the first.Is it a feature or a bug of the compile program? ps, jdk:1.6,IDE:Eclipse 3.5.1

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  • Java Reflection Utility

    - by DD
    Is there a utility to get a property which isnt prefixed by get from an object using reflection similar to BeanUtils? e.g. if I specify "hashcode" and I want to get the object.hashcode() value. Thanks.

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  • Upload files with java

    - by Marius
    I'd like to upload a few files to a http server. Basically what i need is some sort of a post request to the server with a few parameters and the files. I've seen examples of just uploading files, but didn't find how to also pass additional parameters. So the question would be what's the simplest and free solution of doing this? Does anyone have any file upload examples that i could study? I've been googling for a few hours, but (maybe it's just one of those days) couldn't find exactly what i needed. The best solution would be something that doesn't involve any third party classes or libraries. Thank you

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  • get static initialization block to run in a java without loading the class

    - by TP
    I have a few classes as shown here public class TrueFalseQuestion implements Question{ static{ QuestionFactory.registerType("TrueFalse", "Question"); } public TrueFalseQuestion(){} } ... public class QuestionFactory { static final HashMap<String, String > map = new HashMap<String,String>(); public static void registerType(String questionName, String ques ) { map.put(questionName, ques); } } public class FactoryTester { public static void main(String[] args) { System.out.println(QuestionFactory.map.size()); // This prints 0. I want it to print 1 } } How can I change TrueFalseQuestion Type so that the static method is always run so that I get 1 instead of 0 when I run my main method? I do not want any change in the main method. I am actually trying to implement the factory patterns where the subclasses register with the factory but i have simplified the code for this question.

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  • Arrays- Square root of an Array and printing the result JAVA

    - by roger34
    Hello, The title says it all, really. I'm trying to get an array of (9) numbers squared then printed but I keep coming back with only one result - the number of numbers in the array squared- obviously not what I want. Thanks for any help. Ok, here is my terrible code so far. Trying to pass it to a method as well. public static void main ( String args[] ) { double[] nums = {126, 12.939, 795, 320.16, 110, 34.7676, 7773, 67, 567, 323}; System.out.println ("Square root is " +square); square(nums); } public static double square (double [] array) { double result; for( double i = 0; i < array.length ; i++ ) result = Math.sqrt(array[i]); return result; } }

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  • java and threads: very strange behaviour

    - by Derk
    private synchronized Map<Team, StandingRow> calculateStanding() { System.out.println("Calculate standing for group " + getName()); Map<Team, StandingRow> standing = new LinkedHashMap<Team, StandingRow>(); for (Team team : teams) { standing.put(team, new StandingRow(team)); } StandingRow homeTeamRow, awayTeamRow; for (Match match : matches.values()) { homeTeamRow = standing.get(match.getHomeTeam()); awayTeamRow = standing.get(match.getAwayTeam()); System.out.println("Contains key for " + match.getHomeTeam() + ": " + standing.containsKey(match.getHomeTeam())); System.out.println("Contains key for " + match.getAwayTeam() + ": " + standing.containsKey(match.getAwayTeam())); } } This is my code. matches contains 6 elements, but the problem is that after two matches no keys are anymore found in the standing map. The output is for example Contains key for Zuid-Afrika: true Contains key for Mexico: true Contains key for Uruguay: true Contains key for Frankrijk: true Contains key for Zuid-Afrika: false Contains key for Uruguay: false Contains key for Frankrijk: false Contains key for Mexico: false Contains key for Mexico: false Contains key for Uruguay: false Contains key for Frankrijk: false Contains key for Zuid-Afrika: false This is in a threaded environment, but the method is synchronized so I thought that this would not give a problem? I have also a simple unit test for this method and that works well.

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  • java generated excel sorting color mess.

    - by afzal
    I am using jxl api for generating a excel sheet, in which the alternate rows are highlighted, when I sort the contents of a excel and sort manually, the cell background colors messup, usually this is because I am writing the color cell by cell, is there anyway through which i color the alternate rows of the excel while generating it, in such a way that it doesnt effect the sorting of the contents.

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  • goto statements in java

    - by user238284
    I executed the below code in Eclipse, but the GOTO statements in it is not effective. How to use it? case 2: **outsideloops:** System.out.println("Enter the marks (in 100):"); System.out.println("Subject 1:"); float sub1=Float.parseFloat(br.readLine()); **if(sub1<=101) goto outsideloops;** System.out.println("Subject 2:"); float sub2=Float.parseFloat(br.readLine()); System.out.println("Subject 3:"); float sub3=Float.parseFloat(br.readLine()); System.out.println("The Student is "+stu.average(sub1,sub2,sub3)+ "in the examinations"); break;

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  • The best way to assign an immutable instance to a Collection in Java

    - by Ali
    Today I was reading through some Hibernate code and I encounter something interesting. There is a class called CollectionHelper that defines the following constant varibale: public final class CollectionHelper { public static final List EMPTY_LIST = Collections.unmodifiableList( new ArrayList(0 ) ; public static final Collection EMPTY_COLLECTION = Collections.unmodifiableCollection(new ArrayList(0) ); public static final Map EMPTY_MAP = Collections.unmodifiableMap( new HashMap(0) ); They have used these constants to initialize collections with immutable instances. Why they didn't simply use the Collections.EMPTY_LIST for initializing lists? Is there a benefit in using the following method?

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  • Not receiving all message via TCP in Java?

    - by javatcp
    I have a tcp socket sending three lines like this out2.println("message1\n"); out2.println("message2\n"); out2.println("message3\n"); and another tco socket receiving and displaying these messages like this System.out.println(in.readLine()); System.out.println(in.readLine()); System.out.println(in.readLine()); but only the first message is recieved and displayed, anything I send after that is not.

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  • java filenames filter pattern

    - by Sergey
    Hello, I need to implement File[] files = getFiles( String folderName, String ptrn ); Where ptrn is a command prompt style pattern like "*2010*.txt" I'm familar with FilenameFilter class, but can't implement public boolean accept(File dir, String filename) because String.matches() doesn't accept such patterns. Thanks!

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  • java dynamic memory allocation?

    - by JavaUser
    Hi, Why an object initialization using " new " keyword is called as dynamic memory allocation since compile time itself we know the memory needed for that object . Also please explain what happen when u do ClassA object = new ClassA(); in heap and stack . Thx

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