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  • Java JMenuItem Accelator Snow Leopard

    - by Jeremy McGee
    about = new JMenuItem("About"); about.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_A((Toolkit.getDefaultToolkit().getMenuShortcutMask())))); JMenu help = new JMenu("Help"); help.add(about); I was wondering why my aaccelerators were not working. I am running this in snow leopard with JavaSe-1.6 VM. They do work if I pull the menu down then try the key sequence. Thanks

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  • I have a problem with the following Java code

    - by Sanjeev
    public class b { public static void main(String[] args) { byte b = 1; long l = 127; // b = b + l; // 1 if I try this then it does not compile b += l; // 2 if I try this then it does compile System.out.println(b); } } I am using this code but I have problem: I don't understand why b=b+l; is not compiling but if I write b+=l; then it compiles and runs. Please explain why this happens.

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  • Java Simple ActionListener Questions

    - by Allen
    I have a main class in a program that launches another class that handles all the GUI stuff. In the GUI, i have a button that i need to attach an ActionListener to. The only problem is, the code to be executed needs to reside within the main class. How can i get the ActionPerformed() method to execute in the main class when a button is clicked elsewhere?

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  • Using java class HttpsURLConnection

    - by KB22
    Hi all, I have a small piece of code which basically impements a HTTP-Client, i.e. it POSTS request and works with re RESPONSE. As long as HTTP is concenerned everthing work well. For some reason I now have to support HTTPS too. So here is briefly what I do in order to get a connection opened: URL url = new URL(serverAddress); HttpsURLConnection httpsConn = (HttpsURLConnection) url.openConnection(); This fails, stating: sun.net.www.protocol.https.HttpsURLConnectionImpl cannot be cast to com.sun.net.ssl.HttpsURLConnection I guess this is kinda trivial, but I just don't get what I'm doing wrong in this one... Googled it, and the code just looks right - not? any ideas are appreciated! thanks, K

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  • Java: how to use Google's HashBiMap?

    - by HH
    Keys are a file and a word. The file gives all words inside the file. The word gives all files having the word. I am unsure of the domain and co-domain parts. I want K to be of the type <String> and V to be of type <HashSet<FileObject>>. public HashBiMap<K<String>,V<HashSet<FileObject>>> wordToFiles = new HashBiMap<K<String>,V<HashSet<FileObject>>>(); public HashBiMap<K<String>,V<HashSet<FileObject>>> fileToWords = new HashBiMap<K<String>,V<HashSet<FileObject>>>(); Google's HashBiMap.

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  • Java - how to tell class of an object?

    - by lkm
    Given a method that accepts as a parameter a certain supertype. Is there any way, within that method, to determine the actual class of the object that was passed to it? I.e. if a subtype of the allowable parameter was actually passed, is there a way to find out which type it is? If this isn't possible can someone explain why not (from a language design perspective)? Thanks Update: just to make sure I was clear void doSomething(MyType myType) { //determine if myType is MyType OR one of its subclasses } Since the method signature specifies the parameter as being MyType, then how can one tell if the object is actually a subtype of MyType (and which one).

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  • Java Constructor Style (Check parameters aren't null)

    - by Peter
    What are the best practices if you have a class which accepts some parameters but none of them are allowed to be null? The following is obvious but the exception is a little unspecific: public class SomeClass { public SomeClass(Object one, Object two) { if (one == null || two == null) { throw new IllegalArgumentException("Parameters can't be null"); } //... } } Here the exceptions let you know which parameter is null, but the constructor is now pretty ugly: public class SomeClass { public SomeClass(Object one, Object two) { if (one == null) { throw new IllegalArgumentException("one can't be null"); } if (two == null) { throw new IllegalArgumentException("two can't be null"); } //... } Here the constructor is neater, but now the constructor code isn't really in the constructor: public class SomeClass { public SomeClass(Object one, Object two) { setOne(one); setTwo(two); } public void setOne(Object one) { if (one == null) { throw new IllegalArgumentException("one can't be null"); } //... } public void setTwo(Object two) { if (two == null) { throw new IllegalArgumentException("two can't be null"); } //... } } Which of these styles is best? Or is there an alternative which is more widely accepted? Cheers, Pete

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  • Java simple data format british time

    - by DD
    Hi, I am using simple date format to allow users to specify which time zone they are sending data in: DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss,z"); This works fine: e.g. df.parse("2009-05-16 11:07:41,GMT"); However, if someone is always sending time in London time (i.e. taking into account daylight savings), what would be the approriate time zone String to add? e.g. this doesnt work: df.parse("2009-05-16 11:07:41,Europe/London"); Thanks.

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  • Strange problem with simple multithreading program in Java

    - by Elizabeth
    Hello, I am just starting play with multithreading programming. I would like to my program show alternately character '-' and '+' but it doesn't. My task is to use synchronized keyword. As far I have: class FunnyStringGenerator{ private char c; public FunnyStringGenerator(){ c = '-'; } public synchronized char next(){ if(c == '-'){ c = '+'; } else{ c = '-'; } return c; } } class ThreadToGenerateStr implements Runnable{ FunnyStringGenerator gen; public ThreadToGenerateStr(FunnyStringGenerator fsg){ gen = fsg; } @Override public void run() { for(int i = 0; i < 10; i++){ System.out.print(gen.next()); } } } public class Main{ public static void main(String[] args) throws IOException { FunnyStringGenerator FSG = new FunnyStringGenerator(); ExecutorService exec = Executors.newCachedThreadPool(); for(int i = 0; i < 20; i++){ exec.execute(new ThreadToGenerateStr(FSG)); } } } EDIT: I also testing Thread.sleep in run method instead for loop.

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  • some logical error in taking up character in java

    - by Himanshu Aggarwal
    This is my code... class info{ public static void main (String[]args) throws IOException{ char gen; while(true) { //problem occurs with this while System.out.print("\nENTER YOUR GENDER (M/F) : "); gen=(char)System.in.read(); if(gen=='M' || gen=='F' || gen=='m' || gen=='f'){ break; } } System.out.println("\nGENDER = "+gen); } } This is my output... ENTER YOUR GENDER (M/F) : h ENTER YOUR GENDER (M/F) : ENTER YOUR GENDER (M/F) : ENTER YOUR GENDER (M/F) : m GENDER = m Could someone please help me understand why it is asking for the gender so many times.

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  • Java heap size - will this work?

    - by UnCon
    Hi, I try this with NetBeans desktop application template - increasing heapsize (to 512 MiB) of executed .jar file. (I believe that NetBeans uses Singleton app by default - SingleFrameView) Will it work? public static void main(String[] args) { if (args == null) { args = new String[1]; args[0] = "Xmx512m"; } else { String[] tempArgs = new String[args.length+1]; for (int i=0; i<args.length; i++) { tempArgs[i] = args[i]; } tempArgs[tempArgs.length-1] = "Xmx512m"; args = tempArgs; } launch(MyApp.class, args); } }

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  • Java Inheritance - Getting a Parameter from Parent Class

    - by Aaron
    I'm trying to take one parameter from the parent class of Car and add it to my array (carsParked), how can i do this? Parent Class public class Car { protected String regNo; //Car registration number protected String owner; //Name of the owner protected String carColor; /** Creates a Car object * @param rNo - registration number * @param own - name of the owner **/ public Car (String rNo, String own, String carColour) { regNo = rNo; owner = own; carColor = carColour; } /** @return The car registration number **/ public String getRegNo() { return regNo; } /** @return A String representation of the car details **/ public String getAsString() { return "Car: " + regNo + "\nColor: " + carColor; } public String getColor() { return carColor; } } Child Class public class Carpark extends Car { private String location; // Location of the Car Park private int capacity; // Capacity of the Car Park - how many cars it can hold private int carsIn; // Number of cars currently in the Car Park private String[] carsParked; /** Constructor for Carparks * @param loc - the Location of the Carpark * @param cap - the Capacity of the Carpark */ public Carpark (String locations, int room) { location = locations; capacity = room; } /** Records entry of a car into the car park */ public void driveIn() { carsIn = carsIn + 1; } /** Records the departure of a car from the car park */ public void driveOut() { carsIn = carsIn - 1; } /** Returns a String representation of information about the carpark */ public String getAsString() { return location + "\nCapacity: " + capacity + " Currently parked: " + carsIn + "\n*************************\n"; } }

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  • help with reflections and annotations in java

    - by Yonatan
    Hello Internet ! I'm having trouble with doubling up on my code for no reason other than my own lack of ability to do it more efficiently... `for (Method curr: all){ if (curr.isAnnotationPresent(anno)){ if (anno == Pre.class){ for (String str : curr.getAnnotation(Pre.class).value()){ if (str.equals(method.getName()) && curr.getReturnType() == boolean.class && curr.getParameterTypes().length == 0){ toRun.add(curr); } } } if (anno == Post.class) { for (String str : curr.getAnnotation(Post.class).value()){ if (str.equals(method.getName()) && curr.getReturnType() == boolean.class && curr.getParameterTypes().length == 0){ toRun.add(curr); } } } } }` anno is a parameter - Class, and Pre and Post are my annotations, both have a value() which is an array of strings. Of course, this is all due to the fact that i let Eclipse auto fill code that i don't understand yet.

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  • Java JSpinner Prevent Letter Insertion

    - by asmo
    A JSpinner is used to store a number in my application (with a SpinnerNumberModel). As expected, the spinner doesn't allow invalid characters (letters, symbols, etc.) to be stored. However, those characters do appear in the spinner component when I type them in. As soon as I switch the focus to another component, they disappear. Is there a way to prevent invalid characters from appearing in the spinner?

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  • java: retrieving the "canonical value" from a Set<T> where T has a custom equals()

    - by Jason S
    I have a class Foo which overrides equals() and hashCode() properly. I would like to also would like to use a HashSet<Foo> to keep track of "canonical values" e.g. I have a class that I would like to write like this, so that if I have two separate objects that are equivalent I can coalesce them into references to the same object: class Canonicalizer<T> { final private Set<T> values = new HashSet<T>(); public T findCanonicalValue(T value) { T canonical = this.values.get(value); if (canonical == null) { // not in the set, so put it there for the future this.values.add(value); return value; } else { return canonical; } } } except that Set doesn't have a "get" method that would return the actual value stored in the set, just the "contains" method that returns true or false. (I guess that it assumes that if you have an object that is equal to a separate object in the set, you don't need to retrieve the one in the set) Is there a convenient way to do this? The only other thing I can think of is to use a map and a list: class Canonicalizer<T> { // warning: neglects concurrency issues final private Map<T, Integer> valueIndex = new HashMap<T, Integer>(); final private List<T> values = new ArrayList<T>(); public T findCanonicalValue(T value) { Integer i = this.valueIndex.get(value); if (i == null) { // not in the set, so put it there for the future i = this.values.size(); this.values.add(value); this.valueIndex.put(value, i); return value; } else { // in the set return this.values.get(i); } } }

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  • Java days of week calculation

    - by Shahid
    I have an Enum for Days of week (with Everyday, weekend and weekdays) as follows where each entry has an int value. public enum DaysOfWeek { Everyday(127), Weekend(65), Weekdays(62), Monday(2), Tuesday(4), Wednesday(8), Thursday(16), Friday(32), Saturday(64), Sunday(1); private int bitValue; private DaysOfWeek(int n){ this.bitValue = n; } public int getBitValue(){ return this.bitValue; } } Given a TOTAL of any combination of the entries, what would be the simplest way to calculate all individual values and make an arraylist from it. For example given the number 56 (i.e. Wed+Thur+Fri), how to calculate the list of individual values.

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  • Java - Need help with binary/code string manipulation

    - by ShrimpCrackers
    For a project, I have to convert a binary string into (an array of) bytes and write it out to a file in binary. Say that I have a sentence converted into a code string using a huffman encoding. For example, if the sentence was: "hello" h = 00 e = 01, l = 10, o = 11 Then the string representation would be 0001101011. How would I convert that into a byte? <-- If that question doesn't make sense it's because I know little about bits/byte bitwise shifting and all that has to do with manipulating 1's and 0's.

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  • How to keep Java Frame from waiting?

    - by pypmannetjies
    I am writing a genetic algorithm that approximates an image with a polygon. While going through the different generations, I'd like to output the progress to a JFrame. However, it seems like the JFrame waits until the GA's while loop finishes to display something. I don't believe it's a problem like repainting, since it eventually does display everything once the while loop exits. I want to GUI to update dynamically even when the while loop is running. Here is my code: while (some conditions) { //do some other stuff gui.displayPolygon(best); gui.displayFitness(fitness); gui.setVisible(true); } public void displayPolygon(Polygon poly) { BufferedImage bpoly = ImageProcessor.createImageFromPoly(poly); ImageProcessor.displayImage(bpoly, polyPanel); this.setVisible(true); } public static void displayImage(BufferedImage bimg, JPanel panel) { panel.removeAll(); panel.setBounds(0, 0, bimg.getWidth(), bimg.getHeight()); JImagePanel innerPanel = new JImagePanel(bimg, 25, 25); panel.add(innerPanel); innerPanel.setLocation(25, 25); innerPanel.setVisible(true); panel.setVisible(true); }

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  • Filtering out specific objects from a search query in Alfresco using Java

    - by Snowright
    I have a HashSet containing all groups I've retrieved from my database. I've been asked to filter this result by removing two specific groups. It seems trivial but I can't seem to come up with a solid solution for storing the specific groups I want to filter out. My idea is to just create an array containing references to the two groups I need to filter out. I can then filter out my search query with whatever is in the array. My concern is that in the future they may ask to filter out more groups and maybe an array may not be a good idea. //Creates the array containing groups to filter out String[] hiddenGroups = {"group1","group2"}; //retrieves all groups Set<String>allGroups = new HashSet<String>(); allGroups.addAll(authorityService.getAllAuthorities(AuthorityType.GROUP); List<String>results = new ArrayList<String>(); //filters out specified groups for (String group : allGroups) { boolean isHidden = false; for (String hiddenGroup : hiddenGroups) { if (hiddenGroup.equalsIgnorecase(group)) { isHidden = true; } } if (!isHidden){ results.add(group); } }

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  • Java: JPQL search -similar- strings

    - by bguiz
    What methods are there to get JPQL to match similar strings? By similar I mean: Contains: search string is found within the string of the matches entity Case-insensitive Small mispellings: e.g. "arow" matches "arrow" I suspect the first two will be easy, however, I would appreciate help with the last one Thank you

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  • Java Collection performance question

    - by Shervin
    I have created a method that takes two Collection<String> as input and copies one to the other. However, I am not sure if I should check if the collections contain the same elements before I start copying, or if I should just copy regardless. This is the method: /** * Copies from one collection to the other. Does not allow empty string. * Removes duplicates. * Clears the too Collection first * @param target * @param dest */ public static void copyStringCollectionAndRemoveDuplicates(Collection<String> target, Collection<String> dest) { if(target == null || dest == null) return; //Is this faster to do? Or should I just comment this block out if(target.containsAll(dest)) return; dest.clear(); Set<String> uniqueSet = new LinkedHashSet<String>(target.size()); for(String f : target) if(!"".equals(f)) uniqueSet.add(f); dest.addAll(uniqueSet); } Maybe it is faster to just remove the if(target.containsAll(dest)) return; Because this method will iterate over the entire collection anyways.

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  • java.math.BigInteger pow(exponent) question

    - by Jan Kraus
    Hi, I did some tests on pow(exponent) method. Unfortunately, my math skills are not strong enough to handle the following problem. I'm using this code: BigInteger.valueOf(2).pow(var); Results: var | time in ms 2000000 | 11450 2500000 | 12471 3000000 | 22379 3500000 | 32147 4000000 | 46270 4500000 | 31459 5000000 | 49922 See? 2,500,000 exponent is calculated almost as fast as 2,000,000. 4,500,000 is calculated much faster then 4,000,000. Why is that? To give you some help, here's the original implementation of BigInteger.pow(exponent): public BigInteger pow(int exponent) { if (exponent < 0) throw new ArithmeticException("Negative exponent"); if (signum==0) return (exponent==0 ? ONE : this); // Perform exponentiation using repeated squaring trick int newSign = (signum<0 && (exponent&1)==1 ? -1 : 1); int[] baseToPow2 = this.mag; int[] result = {1}; while (exponent != 0) { if ((exponent & 1)==1) { result = multiplyToLen(result, result.length, baseToPow2, baseToPow2.length, null); result = trustedStripLeadingZeroInts(result); } if ((exponent >>>= 1) != 0) { baseToPow2 = squareToLen(baseToPow2, baseToPow2.length, null); baseToPow2 = trustedStripLeadingZeroInts(baseToPow2); } } return new BigInteger(result, newSign); }

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  • What is the purpose of Finalization in java?

    - by Karthik
    Different websites are giving different opinions. My understanding is this: To clean up or reclaim the memory that an object occupies, the Garbage collector comes into action. (automatically is invoked???) The garbage collector then dereferences the object. Sometimes, there is no way for the garbage collector to access the object. Then finalize is invoked to do a final clean up processing after which the garbage collector can be invoked. is this right?

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