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  • Can I avoid repeating myself in this situation (Java)

    - by UltimateGuy
    if (openFile == null) { new AppFileDialog().chooseFile("Save", appFrame); } if (openFile == null) { return; } Here I need to check to see if the user has already chosen a file. If not, they are given a prompt to. If the file is still null, the function returns without saving. The problem is the two identical if statements, can I avoid it? I take DRY very seriously, but at the same time KISS. Ideally the two go hand in hand, but in a situation like this, it seems they are mutually exclusive.

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  • Should I avoid using Java Label Statements?

    - by Kamikaze Mercenary
    Today I had a coworker suggest I refactor my code to use a label statement to control flow through 2 nested for loops I had created. I've never used them before because personally I think they decrease the readability of a program. I am willing to change my mind about using them if the argument is solid enough however. What are people's opinions on label statements?

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  • Ajax file uploading with java back end?

    - by Joren
    I don't want to use flash. I've found multiple jquery libraries that do this. Right now I'm using this one: http://demo.webdeveloperplus.com/ajax-file-upload/ The problem is they all use PHP. I tried just pointing it at my servlet instead of the PHP file, but it never gets called.

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  • Java data structure suggestion.

    - by techoverflow
    Hi folks, I am a newbie in this field so please excuse my silly mistakes :) So the issue I am facing is: On my webpage, I am displaying a table. For now my issue is concerned with three columns of the table. First is : Area Code Second is : Zone Code Third is: Value The relationship between these three is: 1 Area Code has 6 different Zone code's and all those 6 Zone codes have corresponding "Value" I need a data structer that would give me the flexibility to get a "Value" for a Zone code, which falls under a particular Area code. I have the same zone codes for all the Area codes: Zone codes are: 111, 222, 333, 444, 555, 666 After surfing your stackoverflow, I thought I can go with this structure: Map<Integer, Map<Integer, Double>> retailPrices = new HashMap<Integer, Map<Integer, Double>>(); Map<Integer, Double> codes = new HashMap<Integer, Double>(); where reatailPrices would hold an Area Code and a Map of Zone code as Key and "Value" as Value. but when I am trying to populate this through a SQL resultset, I am getting the following error: The method put(Integer, Map<Integer,Double>) in the type Map is not applicable for the arguments (Integer, Double) on line: `while(oResult.next()) retailPrices.put((new Integer(oResult.getString("AREA"))), (pegPlPrices.put(new Integer(oResult.getString("ZONE_CODE")), new Double(oResult.getString("VALUE"))))); }` please help me figure out this problem. Am I following the right approach?

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  • Make Java parent class not part of the interface

    - by Bart van Heukelom
    (This is a hypothetical question for discussion, I have no actual problem). Say that I'm making an implementation of SortedSet by extending LinkedHashMap: class LinkedHashSortedMapThing extends LinkedHashMap implements SortedSet { ... } Now programmers who use this class may do LinkedHashMap x = new LinkedHashSortedMapThing(); But what if I consider the extending of LinkedHashMap an implementation detail, and do not want it to be a part of the class' contract? If people use the line above, I can no longer freely change this detail without worrying about breaking existing code. Is there any way to prevent this sort of thing, other than favouring composition over inheritance (which is not always possible due to private/protected members)?

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  • Java file searching problem

    - by Infinity
    Hello guys! I need to search a file for a word and return the whole line and the line number with this word, then edit the line and write back to the file. Maybe the line number isn't necesary to edit a line in a file. I `was reading after seraching with regexp and opening the filechannel of the file, but I can't get the line number. Maybe there are other better ways to do this. Can you help me how to start this?

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  • how to display a image in java application after downloading the image

    - by Nubkadiya
    i want to display a image after downloading that image from a web-server i have wrote the code for downloading the image. but i cant set it up to a label or any thing other than jframe (because i want to add more buttons and labels to the GUI). here is the code to download the image from the webserver. now i want to set it to a label. please help me URL url = new URL("http://www.personal.psu.edu/acr117/blogs/audrey/images/image-2.jpg"); image = ImageIO.read(url);

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  • Java convert JSONObject to URL parameter

    - by Alex Ivasyuv
    What is the elegant way to convert JSONObject to URL parameters. For example, JSONObject: {stat: {123456: {x: 1, y: 2}, 123457: {z: 5, y: 2}}}} this should be like: stat[123456][x]=1&stat[123456][y]=2&stat[123457][z]=5&stat[123457][y]=2 of course with escaped symbols, and of course JSON object could be more complicated.. Maybe there already exist some mechanisms for that? Thanks,

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  • java : how to handle the design when template methods throw exception when overrided method not throw

    - by jiafu
    when coding. try to solve the puzzle: how to design the class/methods when InputStreamDigestComputor throw IOException? It seems we can't use this degisn structure due to the template method throw exception but overrided method not throw it. but if change the overrided method to throw it, will cause other subclass both throw it. So can any good suggestion for this case? abstract class DigestComputor{ String compute(DigestAlgorithm algorithm){ MessageDigest instance; try { instance = MessageDigest.getInstance(algorithm.toString()); updateMessageDigest(instance); return hex(instance.digest()); } catch (NoSuchAlgorithmException e) { LOG.error(e.getMessage(), e); throw new UnsupportedOperationException(e.getMessage(), e); } } abstract void updateMessageDigest(MessageDigest instance); } class ByteBufferDigestComputor extends DigestComputor{ private final ByteBuffer byteBuffer; public ByteBufferDigestComputor(ByteBuffer byteBuffer) { super(); this.byteBuffer = byteBuffer; } @Override void updateMessageDigest(MessageDigest instance) { instance.update(byteBuffer); } } class InputStreamDigestComputor extends DigestComputor{ // this place has error. due to exception. if I change the overrided method to throw it. evey caller will handle the exception. but @Override void updateMessageDigest(MessageDigest instance) { throw new IOException(); } }

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  • Java copyOf method problem with an Array of Objects

    - by Greg
    elementData = Arrays.copyOf(elementData, newCapacity); Gives error: "The method copyOf(Object[], int) is undefined for the type Arrays" This was not a problem on my home computer, but at my school's it gives the error above. I'm guessing it's running an older JRE version - any workaround? Thanks

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  • Java do while, while

    - by Pindatjuh
    Hello, what behaviour can I expect when I run this code: do while(testA) { // do stuff } while(testB); Will it behave like: do { while(testA) { // do stuff } } while(testB); Or: if(testA) { do { // do stuff } while(testA && testB); } Or something totally unexpected? I ask this question because I think this is quite ambiguous, and for other people searching on this topic, not because I am lazy to test it out.

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  • Java: BufferedImage from raw BMP file format data

    - by Victor
    Hello there. I've got BMP file's raw pixels table in byte[], it's structure is: (b g r) (b g r) ... (b g r) padding ... (b g r) (b g r) ... (b g r) padding Where r, g, b are byte each, padding is to round row length up to a multiple of 4 bytes. So, how can I create new BufferedImage from this raw data without copying, just using this raw data? I took a look at creating BufferedImage from DataBuffer, but I just didn't get it. Unfortunately ImageIO is not allowed in my situation.

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  • Java Beginner question about String[] args in the main method

    - by happysoul
    So I just tried excluding String[] args from the main method It compiled alright ! But JVM is showing an exception Why did it compile when String[] args HAS to be included every time ? What is going on here ? Why won't it show a compilation error ? typing this made me think that may be compiler did not see it as THE main method ..is that so ?

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  • Detect if Java Swing component has been hidden

    - by kayahr
    Assume we have the following Swing application: final JFrame frame = new JFrame(); final JPanel outer = new JPanel(); frame.add(outer); JComponent inner = new SomeSpecialComponent(); outer.add(inner); So in this example we simply have an outer panel in the frame and a special component in the panel. This special component must do something when it is hidden and shown. But the problem is that setVisible() is called on the outer panel and not on the special component. So I can't override the setVisible method in the special component and I also can't use a component listener on it. I could register the listener on the parent component but what if the outer panel is also in another panel and this outer outer panel is hidden? Is there an easier solution than recursively adding componentlisteners to all parent components to detect a visibility change in SomeSpecialComponent?

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  • Profiling a Java Spring application

    - by niklassaers
    Hi guys, I have a Spring application that I believe has some bottlenecks, so I'd like to run it with a profiler to measure what functions take how much time. Any recommendations to how I should do that? I'm running STS, the project is a maven project, and I'm running Spring 3.0.1 Cheers Nik

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  • Java/Swing: Problem with key listener

    - by Mike
    I have a search dialog with a JTextField that's being used as a search box. When the user types something, it searches the DB, shows the result in a JTable and selects the first item in it. If the first result is what they were looking for, I want to let them quickly accept the dialog, by pressing Enter (while the JTextField is focused). So I added a KeyListener to the JTextField and it's working OK. Now the problem: The user opens can open the dialog by pressing Enter when a "Search" button on the dialog's parent frame is focused. The dialog is displayed and the JTextField gets the keyReleased event (from the Enter key that displayed it), so it shows up and closes. If the user holds Enter down, then the JTextField receives the keyPressed, keyTyped and keyReleased events. How can I fix without resorting to ugly workarounds? Platform is Windows 7 x64, btw. Test NetBeans project here: http://dl.dropbox.com/u/6354360/KeyListenerTest.zip Thanks.

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  • Java Web App: Passing form parameters across multiple pages

    - by digiarnie
    Hi, what is the best practice or best way of passing form parameters from page to page in a flow? If I have a flow where a user enters data in a form and hits next and repeats this process until they get to an approval page, what ways could I approach this problem to make the retention of data as simple as possible over the flow? I guess you could put all the information as you go in the session but could you get into memory issues if a lot of people are using your app and going through the flow at the same time?

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  • Java BoxLayout alignment issue

    - by ManInMoon
    Can anyone help me. Why is the Label "Current" NOT left aligned in Panel/Frame? public static void main(String[] args) { JFrame TFrame = new JFrame("Test DisplayLayout"); TFrame.setResizable(true); TFrame.setSize(new Dimension(900, 840)); TFrame.setLocationRelativeTo(null); TFrame.setTitle("DisplayLayout"); TFrame.setVisible(true); JPanel P = DisplayLayout2(); P.setVisible(true); P.setOpaque(true); P.setLayout(new BoxLayout(P, BoxLayout.Y_AXIS)); TFrame.add(P); TFrame.revalidate(); TFrame.repaint(); } public static JPanel DisplayLayout2() { JPanel Panel=new JPanel(); Panel.setVisible(true); Panel.setOpaque(true); Panel.setLayout(new BoxLayout(Panel, BoxLayout.Y_AXIS)); Panel.setAlignmentX(Component.LEFT_ALIGNMENT); JLabel lab = new JLabel("Current"); lab.setHorizontalAlignment(SwingConstants.LEFT); lab.setForeground(Color.WHITE); lab.setBackground(Color.PINK); lab.setOpaque(true); Panel.add(lab,Component.LEFT_ALIGNMENT); JPanel posPanel = new JPanel(); JScrollPane scrollPane = new JScrollPane(posPanel,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_NEVER); scrollPane.setPreferredSize(new Dimension(290, 200)); scrollPane.setOpaque(true); posPanel.setBackground(Color.YELLOW); posPanel.setPreferredSize(new Dimension(290, 200)); posPanel.setLayout(new BoxLayout(posPanel, BoxLayout.Y_AXIS)); posPanel.setAlignmentX(Component.LEFT_ALIGNMENT); Panel.add(scrollPane); return Panel; }

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  • Check a Date is between two dates in Java

    - by dimitar
    Hello guys, One thing I want to know is how to calculate what date will it be 10 days from today. Second thing is to check if one Date is between two other Dates. For example, let's say I have an app that shows what events I need to do in the next 10 days (planner). Now how can I see if the date I assigned to an event is between today and the date that is 10 days from today?

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  • Java algorithm for normalizing audio

    - by Marty Pitt
    I'm trying to normalize an audio file of speech. Specifically, where an audio file contains peaks in volume, I'm trying to level it out, so the quiet sections are louder, and the peaks are quieter. I know very little about audio manipulation, beyond what I've learnt from working on this task. Also, my math is embarrassingly weak. I've done some research, and the Xuggle site provides a sample which shows reducing the volume using the following code: (full version here) @Override public void onAudioSamples(IAudioSamplesEvent event) { // get the raw audio byes and adjust it's value ShortBuffer buffer = event.getAudioSamples().getByteBuffer().asShortBuffer(); for (int i = 0; i < buffer.limit(); ++i) buffer.put(i, (short)(buffer.get(i) * mVolume)); super.onAudioSamples(event); } Here, they modify the bytes in getAudioSamples() by a constant of mVolume. Building on this approach, I've attempted a normalisation modifies the bytes in getAudioSamples() to a normalised value, considering the max/min in the file. (See below for details). I have a simple filter to leave "silence" alone (ie., anything below a value). I'm finding that the output file is very noisy (ie., the quality is seriously degraded). I assume that the error is either in my normalisation algorithim, or the way I manipulate the bytes. However, I'm unsure of where to go next. Here's an abridged version of what I'm currently doing. Step 1: Find peaks in file: Reads the full audio file, and finds this highest and lowest values of buffer.get() for all AudioSamples @Override public void onAudioSamples(IAudioSamplesEvent event) { IAudioSamples audioSamples = event.getAudioSamples(); ShortBuffer buffer = audioSamples.getByteBuffer().asShortBuffer(); short min = Short.MAX_VALUE; short max = Short.MIN_VALUE; for (int i = 0; i < buffer.limit(); ++i) { short value = buffer.get(i); min = (short) Math.min(min, value); max = (short) Math.max(max, value); } // assign of min/max ommitted for brevity. super.onAudioSamples(event); } Step 2: Normalize all values: In a loop similar to step1, replace the buffer with normalized values, calling: buffer.put(i, normalize(buffer.get(i)); public short normalize(short value) { if (isBackgroundNoise(value)) return value; short rawMin = // min from step1 short rawMax = // max from step1 short targetRangeMin = 1000; short targetRangeMax = 8000; int abs = Math.abs(value); double a = (abs - rawMin) * (targetRangeMax - targetRangeMin); double b = (rawMax - rawMin); double result = targetRangeMin + ( a/b ); // Copy the sign of value to result. result = Math.copySign(result,value); return (short) result; } Questions: Is this a valid approach for attempting to normalize an audio file? Is my math in normalize() valid? Why would this cause the file to become noisy, where a similar approach in the demo code doesn't?

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