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  • How do I check if a variable has been initialized

    - by Javier Parra
    First of all, I'm fairly new to Java, so sorry if this question is utterly simple. The thing is: I have a String[] s made by splitting a String in which every item is a number. I want to cast the items of s into a int[] n. s[0] contains the number of items that n will hold, effectively s.length-1. I'm trying to do this using a foreach loop: int[] n; for(String num: s){ //if(n is not initialized){ n = new int[(int) num]; continue; } n[n.length] = (int) num; } Now, I realize that I could use something like this: int[] n = new int[(int) s[0]]; for(int i=0; i < s.length; i++){ n[n.length] = (int) s[i]; } But I'm sure that I will be faced with that "if n is not initialized initialize it" problem in the future.

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  • Problem with loading a PNG image in JApplet.

    - by Bruce
    Hi there, I'm trying to load a PNG image from JAR file when running JApplet. The file is, I think, loaded properly - there are no errors. However it is not displayed. img.png is placed in the same directory as MainClass.java file. Here is the code: InputStream imageURL = this.getClass().getResourceAsStream("img.png" ); byte[] bytes = null; try {bytes = new byte[imageURL.available()]; System.out.println(imageURL.available()); imageURL.read(bytes);} catch(Exception e) {System.out.println("bleah");} Image image = Toolkit.getDefaultToolkit().createImage(bytes); Image imageScaled = me.getScaledInstance( 100, 150, Image.SCALE_SMOOTH ); jLabel6 = new javax.swing.JLabel( new ImageIcon( imageScaled) ); and the HTML exerpt: <APPLET codebase="classes" code="myapplet/MainClass.class" archive ="LittleApplet.jar" width=700 height=500> The image, as I wrote, is probably read, but not displayed in JLabel. What am I missing/doing wrong? Thanks in advance for the reply!

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  • What is the correct stage to use for Google Guice in production in an application server?

    - by Yishai
    It seems like a strange question (the obvious answer would Production, duh), but if you read the java docs: /** * We want fast startup times at the expense of runtime performance and some up front error * checking. */ DEVELOPMENT, /** * We want to catch errors as early as possible and take performance hits up front. */ PRODUCTION Assuming a scenario where you have a stateless call to an application server, the initial receiving method (or there abouts) creates the injector new every call. If there all of the module bindings are not needed in a given call, then it would seem to have been better to use the Development stage (which is the default) and not take the performance hit upfront, because you may never take it at all, and here the distinction between "upfront" and "runtime performance" is kind of moot, as it is one call. Of course the downside of this would appear to be that you would lose the error checking, causing potential code paths to cause a problem by surprise. So the question boils down to are the assumptions in the above correct? Will you save performance on a large set of modules when the given lifetime of an injector is one call?

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  • Why is the main method not covered?

    - by Mike.Huang
    main method: public static void main(String[] args) throws Exception { if (args.length != EXPECTED_NUMBER_OF_ARGUMENTS) { System.err.println("Usage - java XFRCompiler ConfigXML PackageXML XFR"); } String configXML = args[0]; String packageXML = args[1]; String xfr = args[2]; AutoConfigCompiler compiler = new AutoConfigCompiler(); compiler.setConfigDocument(loadDocument(configXML)); compiler.setPackageInfoDoc(loadDocument(packageXML)); // compiler.setVisiblityDoc(loadDocument("VisibilityFilter.xml")); compiler.compileModel(xfr); } private static Document loadDocument(String fileName) throws Exception { TXDOMParser parser = (TXDOMParser) ParserFactory.makeParser(TXDOMParser.class.getName()); InputSource source = new InputSource(new FileInputStream(fileName)); parser.parse(source); return parser.getDocument(); } testcase: @Test public void testCompileModel() throws Exception { // construct parameters URL configFile = Thread.currentThread().getContextClassLoader().getResource("Ford_2008_Mustang_Config.xml"); URL packageFile = Thread.currentThread().getContextClassLoader().getResource("Ford_2008_Mustang_Package.xml"); File tmpFile = new File("Ford_2008_Mustang_tmp.xfr"); if(!tmpFile.exists()) { tmpFile.createNewFile(); } String[] args = new String[]{configFile.getPath(),packageFile.getPath(),tmpFile.getPath()}; try { // test main method XFRCompiler.main(args); } catch (Exception e) { assertTrue(true); } try { // test args length is less than 3 XFRCompiler.main(new String[]{"",""}); } catch (Exception e) { assertTrue(true); } tmpFile.delete(); } Coverage outputs displayed as the lines from String configXML = args[0]; in main method are not covered.

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  • Use of 'super' keyword when accessing non-overridden superclass methods

    - by jonny
    I'm trying to get the hang of inheritance in Java and have learnt that when overriding methods (and hiding fields) in sub classes, they can still be accessed from the super class by using the 'super' keyword. What I want to know is, should the 'super' keyword be used for non-overridden methods? Is there any difference (for non-overridden methods / non-hidden fields)? I've put together an example below. public class Vehicle { public int tyreCost; public Vehicle(int tyreCost) { this.tyreCost = tyreCost; } public int getTyreCost() { return tyreCost; } } and public class Car extends Vehicle { public int wheelCount; public Vehicle(int tyreCost, int wheelCount) { super(tyreCost); this.wheelCount = wheelCount; } public int getTotalTyreReplacementCost() { return getTyreCost() * wheelCount; } } Specifically, given that getTyreCost() hasn't been overridden, should getTotalTyreReplacementCost() use getTyreCost(), or super.getTyreCost() ? I'm wondering whether super should be used in all instances where fields or methods of the superclass are accessed (to show in the code that you are accessing the superclass), or only in the overridden/hidden ones (so they stand out).

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  • Importing external .jar file to Android project

    - by robintw
    I've read various answers to similar questions on StackOverflow, so I apologise if I'm repeating another question, but I can't seem to get this to work. I have a standard java project in which I've written code to parse some BBC Radio XML data from the internet. The project is called BBCSchedules and the class I'm interested in is called BBCChannel. I'm now trying to use the BBCChannel class in an android application. How should I go about doing this? I've tried various things, following various bits of advice on the internet, and the place I've got to at the moment is compiling my BBCSchedules project to a .jar file, and importing that to the Android project using the Build Path/Library/Add External Jar option. However, Eclispe still doesn't recognise the BBCChannel class, and won't let me run the application because of this. I guess I've done something silly wrong, but what is it? Cheers, Robin UPDATE: I've tried the steps listed in http://stackoverflow.com/questions/1334802/how-can-i-use-external-jars-in-an-android-project and various other StackOverflow questions I can find that seem to be related to this, but absolutely nothing seems to work. Any other ideas? UPDATE: The discussions I've had with the author of the first answer below suggest that it is something to do with how I am using Eclipse to attach the .jar file. The project he sent me with the .jar file already attached didn't work. Any other ideas anyone?

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  • Open source real life license examples: yours or others

    - by donpal
    I'm aware of the usual list of open source licenses, so I'm not even going to list it here. What I'd like to ask is about your open source projects (whether out or planned for the future), and why you're planning to choose a certain license over the other. Basically say I went for X license because I wanted Y and that other license didn't provide it for me. I understand that the language itself can make a difference in the choice of license: interpreted languages like PHP vs. compiled languages like Java. I'm mostly interested in hearing about PHP projects, but of course additional insights are welcome. You may even have chosen that particular language for a licensing reason. Ideally I want to hear answers from people who were involved in the actual project (i.e. your own project), because that usually means you've put some thought into the license yourself and understand the implications of that license. But examples of existing projects that aren't your own are OK. Please just say why you think that license was good/bad for them. But first-hand experience is preferred. Looking forward to hearing some informative input.

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  • In which year was the date the same as the original year?

    - by Marta
    It's my first question on this site, but I always found this site really useful. What I mean with my question is: you ask the person to give a date (eg. Fill in a date [dd-mm-yyyy]: 16-10-2013) you than have to ask an interval between 2 years (eg. Give an interval [yyyy-yyyy]:1800-2000) When the program runs, it has to show what day of the week the given date is. In this case it was a Wednesday. Than the program has to look in which year, in between the interval, the date 16 October also fell on a Wednesday. So in the end it has to look something like this: Fill in a date: [dd-mm-yyyy]: 16-10-2013 Give an interval [yyyy-yyyy]: 1900-2000 16 October was a wednesday in the following years: 1905 1911 1916 1922 1933 1939 1944 1950 1961 1967 1972 1978 1989 1995 2000 The full date is Wednesday 16 October, 2013 The small (or biggest) problem is, I am not allowed to use the DATE.function in java. If someone can help me with the second part I would be really really happy, cause I have no idea how I am supposed to do this To find out what day of the week the given date falls, I use the Zeller Congruence class Day { Date date; //To grab the month and year form the Date class int day; final static String[] DAYS_OF_WEEK = { "Saturday", "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday" }; public void dayWeekInterval{ //code to grab the interval from interval Class, and doing stuff here } public void dayOfTheWeek { int m = date.getMonth(); int y = date.getYear(); if (m < 3) { m += 12; y -= 1; } int k = y % 100; int j = y / 100; int day = ((q + (((m + 1) * 26) / 10) + k + (k / 4) + (j / 4)) + (5 * j)) % 7; return day; } public string ToString(){ return "" + DAYS_OF_WEEK[day] + day; } }

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  • Am I doing it right?

    - by LuckySlevin
    I have situation. I have to create a Sports Club system in JAVA. There should be a class your for keeping track of club name, president name and braches the club has. For each sports branch also there should be a class for keeping track of a list of players. Also each player should have a name, number, position and salary. So, I come up with this. Three seperate classes: public class Team { String clubName; String preName; Branch []branches; } public class Branch { Player[] players; } public class Player { String name; String pos; int salary; int number; } The problems are creating Branch[] in another class and same for the Player[]. Is there any simplier thing to do this? For example, I want to add info for only the club name, president name and branches of the club, in this situation, won't i have to enter players,names,salaries etc. since they are nested in each other. I hope i could be clear. For further questions you can ask.

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  • JVM to ignore certificate name mismatch

    - by Heavy Bytes
    I know there were a lot of questions/answers about how to ignore SSL error in the code. On our dev region dev.domain.tld we have configured a app server over SSL. The certificate that is displayed is for somedev.domain.tld. There is no way to change the certificate, it will always be a domain mismatch. So when I deploy a web-service to https://dev.domain.tld and try to connect/call my webservice I get an exception: Caused by: java.security.cert.CertificateException: No name matching dev.domain.tld found And I have the somedev.domain.tld CERT in my trust store. Now, I saw a lot of samples how to change that in the code (using a Trust Manager that accepts all domains), but how do I specify to the JVM to ignore the domain mismatch when connecting to the server? Is there a -Djavax.net.ssl argument or something? Thank you! UPDATE: Or, since I am using Spring-WS, is there a way to set some property in Spring for that? (WebServiceTemplate) UPDATE I guess I'll have to do use something from Spring Security: http://static.springsource.org/spring-ws/sites/1.5/reference/html/security.html

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  • Hash Code for a group of three fields

    - by Gauranga
    I have three fields namely Number1 Number2 Time I am trying to write a function in java that returns a unique hash value (long needs to be the return type of hash) for the above fields. This hash would then be used to store database rows corresponding to the above mentioned fields in a HashSet. I am new to writing a hash code function, can someone please review what I have. Any help would be appreciated. public class HashCode { private long Number1; private long Number2; String Time; public HashCode(long Number1, long Number2, String Time){ this.Number1 = Number1; this.Number2 = Number2; this.Time = Time; } public long getHashCode() { long hash = 3; hash = 47 * hash + (long) (this.Number1 ^ (this.Number1 >>> 32)); hash = 47 * hash + (long) (this.Number2 ^ (this.Number2 >>> 32)); hash = 47 * hash + (this.Time != null ? this.Time.hashCode() : 0); return hash; } }

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  • To use the 'I' prefix for interfaces or not to

    - by ng
    That is the question? So how big a sin is it not to use this convention when developing a c# project? This convention is widely used in the .NET class library. However, I am not a fan to say the least, not just for asthetic reasons but I don't think it makes any contribution. For example is IPSec an interface of PSec? Is IIOPConnection An interface of IOPConnection, I usually go to the definition to find out anyway. So would not using this convention cause confusion? Are there any c# projects or libraries of note that drop this convention? Do any c# projects that mix conventions, as unfortunately Apache Wicket does? The Java class libraries have existed without this for many years, I don't feel I have ever struggled to read code without it. Also, should the interface not be the most primitive description? I mean IList<T> as an interface for List<T> in c#, is it not better to have List<T> and LinkedList<T> or ArrayList<T> or even CopyOnWriteArrayList<T>? The classes describe the implementation? I think I get more information here, than I do from List<T> in c#.

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  • Programmatic Text Wrapping in TextView

    - by Andrew
    I'm working on a custom widget for my application to replicate the look of a Preference button for layouts. The issue is the 'summary' text wont wrap when it hits the right wall of the view. One of the goals I'm trying to keep is that this widget is completely made from java with no xml attributes. here's what the widget looks like at the moment: http://dl.dropbox.com/u/56017670/Screenshot_2012-09-05-17-22-45.png notice that the middle two don't wrap the text but the text obviously runs right off the edge of the widget below is the code I'm using to create the text view. public void setSummary(String summary) { if (!TextUtils.isEmpty(summary)) { if (mSummaryView == null) { mSummaryView = new TextView(mContext); mSummaryView.setTextSize(14); mSummaryView.setTextColor(mContext.getResources().getColor( android.R.color.tertiary_text_dark)); addView(mSummaryView); } mSummaryView.setText(summary); mSummaryView.setVisibility(View.VISIBLE); } else { if (mSummaryView != null) { mSummaryView.setVisibility(View.GONE); } } mSummaryText = summary; } and here is the code I'm using to layout mSummaryView mSummaryView.layout( mPreferencePadding + mIconWidth, centerVertical + (mCombinedTextHeight / 2) - mSummaryHeight, width - mPreferencePadding, centerVertical + (mCombinedTextHeight / 2)); I've tried to add mSummaryView.setSingleLine(false); along with quite a few other tricks but they all ended in the same way.

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  • How do I send data between two computers over the internet

    - by Johan
    I have been struggling with this for the entire day now, I hope somebody can help me with this. My problem is fairly simple: I wish to transfer data (mostly simple commands) from one PC to another over the internet. I have been able to achieve this using sockets in Java when both computers are connected to my home router. I then connected both computers to the internet using two different mobile phones and attempted to transmit the data again. I used the mobile phones as this provides a direct route to the internet and if I use my router I have to set up port forwarding, at least, that is how I understand it. I think the problem lies in the method that I set up the client socket. I used: Socket kkSocket = new Socket(ipAddress, 3333); where ipAddress is the IP address of the computer running the server. I got the IP address by right-clicking on the connection, status, support. Is that the correct IP address to use or where can I obtain the address of the server? Also, is it possible to get a fixed name for my computer that I can use instead of entering the IP address, as this changes every time I connect to the internet using my mobile phone? Alternatively, are there better methods to solving my problem such as using http, and if so, where can I find more information about this? Thanks!

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  • Connect.registerUsers - Need helping creating array for accounts param

    - by mw_javaguy
    I keep getting the following error when I try to invoke the Facebook REST API Call: Connect.registerUsers Error Code: 100 - param accounts must be an array JSON based response (from Facebook): {"error_code":100,"error_msg":"param accounts must be an array.","request_args": [{"key":"accounts","value":"{email_hash:5232156322_55ddgvc3db5ddcf218049dd564da2x06}"}, {"key":"api_key","value":"23b2c4c6a23445fbffssf8aab96a5e5"}, {"key":"format","value":"JSON"},{"key":"method","value":"Connect.registerUsers"},{"key":"sig","value":"3sd54153a31382fa6e72eecf3c57d7c9"},{"key":"v","value":"1.0"}],"message":"Unknown exception","code":0} I set up the Java code to invoke the REST end point using HttpClient like this: String API_KEY = "23b2c4c6a23445fbffssf8aab96a5e5"; String toConnectRegisterUsersSignature = "accounts=" + "{email_hash:" + emailHash + "}" + "api_key=" + API_KEY + "format=JSON" + "method=Connect.registerUsers" + "v=1.0" + "0c786155bd3cxe8228d924542da5gf2"; String connectRegisterUsersSignature = SimpleMd5.MD5(toConnectRegisterUsersSignature); NameValuePair[] connectRegisterUsersParameters = { new NameValuePair("accounts", "{email_hash:" + emailHash + "}"), new NameValuePair("api_key", API_KEY), new NameValuePair("format", "JSON"), new NameValuePair("method", "Connect.registerUsers"), new NameValuePair("sig", connectRegisterUsersSignature), new NameValuePair("v", "1.0") }; Tried the following combinations and I still get the same error! Signature: "accounts=" + "[email_hash=" + emailHash + "]" new NameValuePair("accounts", "[email_hash=" + emailHash + "]") Signature: "accounts=" + "email_hash[" + emailHash + "]" new NameValuePair("accounts", "email_hash[" + emailHash + "]") Signature: "accounts=" + "email_hash(" + emailHash + ")" new NameValuePair("accounts", "email_hash(" + emailHash + ")") Signature: "accounts=" + "[email_hash=" + emailHash + "]" new NameValuePair("accounts", "[email_hash=" + emailHash + "]") Signature: "accounts=" + "email_hash=" + emailHash new NameValuePair("accounts", "email_hash=" + emailHash) Signature: "accounts=" + "[{email_hash:" + emailHash + "}]" new NameValuePair("accounts", "[{email_hash:" + emailHash + "}]"), Does anyone know how to construct this array that the response is requesting? Happy programming and thank you for taking the time to read this.

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  • Auto scale and rotate images

    - by Dave Jarvis
    Given: two images of the same subject matter; the images have the same resolution, colour depth, and file format; the images differ in size and rotation; and two lists of (x, y) co-ordinates that correlate the images. I would like to know: How do you transform the larger image so that it visually aligns to the second image? (Optional.) What are the minimum number of points needed to get an accurate transformation? (Optional.) How far apart do the points need to be to get an accurate transformation? The transformation would need to rotate, scale, and possibly shear the larger image. Essentially, I want to create (or find) a program that does the following: Input two images (e.g., TIFFs). Click several anchor points on the small image. Click the several corresponding anchor points on the large image. Transform the large image such that it maps to the small image by aligning the anchor points. This would help align pictures of the same stellar object. (For example, a hand-drawn picture from 1855 mapped to a photograph taken by Hubble in 2000.) Many thanks in advance for any algorithms (preferably Java or similar pseudo-code), ideas or links to related open-source software packages.

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  • JSTL <c:out> where the element name contains a space character...

    - by Shane
    I have an array of values being made available, but unfortunately some of the variable names include a space. I cannot work out how to simply output these in the page. I know I'm not explaining this well (I'm the JSP designer, not the Java coder) so hopefully this example will illustrate what I'm trying to do: <c:out value="${x}"/> outputs to the page (artificially wrapped) as: {width=96.0, orderedheight=160.0, instructions=TEST ONLY. This is a test., productId=10132, publication type=ns, name=John} I can output the name by using <c:out value="${x.name}"/> no problems. The issue is when I try to get the "publication type"... because it has a space, I can't seem to get <c:out> to display it. I have tried: <!-- error parsing custom action attribute: --> <c:out value="${x.publication type}"/> <!-- error occurred while evaluating custom action attribute: --> <c:out value="${x.publication+type}"/> <!-- error occurred while parsing custom action attribute: --> <c:out value="${x.'publication type'}"/> <!-- error occurred while parsing custom action attribute: --> <c:out value="${x.publication%20type}"/> I know the real solution is to get the variable names formatted correctly (ie: without spaces) but I can't get the code updated for quite a while. Can this be done? Any help greatly appreciated.

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  • Maven + AspectJ - all steps to configure it

    - by Alice
    I have a problem with applying aspects to my maven project. Probably I am missing something, so I've made a list of steps. Could you please check if it is correct? Let say in projectA is an aspect class and in projectB classes, which should be changed by aspects. Create maven project ProjectA with AspectJ class add Aspectj plugin and dependency Add ProjectA as a dependency to projectB pom.xml Add to projectB pom.xml plugin " <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>aspectj-maven-plugin</artifactId> <version>1.4</version> <executions> <execution> <goals> <goal>compile</goal> <goal>test-compile</goal> </goals> </execution> </executions> <configuration> <source>${maven.compiler.source}</source> <target>${maven.compiler.target}</target> <aspectLibraries> <aspectLibrary> <groupId>ProjectA</groupId> <artifactId>ProjectA</artifactId> </aspectLibrary> </aspectLibraries> </configuration> </plugin> Add aspectj dependency After all these steps my problem is, that during compilation I get: [WARNING] advice defined in AspectE has not been applied [Xlint:adviceDidNotMatch] And then when I run my program: Exception in thread "FeatureExcutionThread" java.lang.NoClassDefFoundError: AspectE

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  • Can we have a component-scoped bean in a JSF2 composite component?

    - by Pradyumna
    Hi, I was wondering how I could create "component-scoped" beans, or so-to-say, "local variables inside a composite component" that are private to the instance of the composite component, and live as long as that instance lives. Below are more details, explained with an example: Suppose there is a "calculator" component - something that allows users to type in a mathematical expression, and evaluates its value. Optionally, it also plots the associated function. I can make a composite component that has: a text box for accepting the math expression two buttons called "Evaluate", and "Plot" another nested component that plots the function It is evidently a self-contained piece of function; so that somebody who wants to use it may just say <math:expressionEvaluator /> But obviously, the implementation would need a java object - something that evaluates the expression, something that computes the plot points, etc. - and I imagine it can be a bean - scoped just for this instance of this component, not a view-scoped or request-scoped bean that is shared across all instances of the component. How do I create such a bean? Is that even possible with composite components?

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  • Doubly Linked Lists Implementation

    - by user552127
    Hi All, I have looked at most threads here about Doubly linked lists but still unclear about the following. I am practicing the Goodrich and Tamassia book in Java. About doubly linked lists, please correct me if I am wrong, it is different from a singly linked list in that a node could be inserted anywhere, not just after the head or after the tail using both the next and prev nodes available, while in singly linked lists, this insertion anywhere in the list is not possible ? If one wants to insert a node in a doubly linked list, then the default argument should be either the node after the to-be inserted node or node before the to-be inserted node ? But if this is so, then I don't understand how to pass the node before or after. Should we be displaying all nodes that were inserted till now and ask the user to select the node before or after which some new node is to be inserted ? My doubt is how to pass this default node. Because I assume that will require the next and prev nodes of these nodes as well. For e.g, Head<-A<-B<-C<-D<-E<-tail If Z is the new node to be inserted after say D, then how should node D be passed ? I am confused with this though it seems pretty simple to most. But pl do explain. Thanks, Sanjay

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  • Eclipse cannot find existing project in build path

    - by PNS
    Here is probably one of the idiosyncrasies of Eclipse and its handling of build paths, which cannot be fixed despite all sorts of workarounds tested so far. The issue relates to a workspace of several projects, each of which compiles into its own JAR. Dependencies among the projects are resolved by adding the relevant ones to the build path (no Maven or other external tool or plugin is used), via Project -> Properties -> Java Build Path -> Projects Among all these projects, a couple (say, com.example.p1 and com.example.p2) refuse to recognize a third (and simple) one (say, com.example.p3), while all other projects do. So, although P3 is added to the build path, all related classes from P3 are imported properly and the source code of each such class is accessible by hitting F3, Eclipse keeps complaining that The import com.example.p3 cannot be resolved and SomeClass cannot be resolved to a type where com.example.p3.SomeClass is one of the P3 classes. If instead of the P3 project I put its compiled JAR in the build path, the issue disappears. However, code in P3 changes frequently and it is a time waste to keep compiling and refreshing the workspace so that the change is picked up, not to mention that this should not happen in an IDE anyway (and it does not for the other projects using P3). Among the workarounds tried are things like: Removing and adding again P1, P2, P3 Cleaning up and recompiling everything Checking whether any other project loads the P3 JAR Putting P3 at the top of the Eclipse build path "Order and Export" list Using the "Fix project setup" suggestion of Eclipse (available when hovering the mouse over the red-underlined-error compilation line). Actually, this option offers adding to the build path either P3 or its JAR, but if P3 is added, the issue reappears. Any ideas?

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  • Code Golf: Counting XML elements in file on Android

    - by CSharperWithJava
    Take a simple XML file formatted like this: <Lists> <List> <Note/> ... <Note/> </List> <List> <Note/> ... <Note/> </List> </Lists> Each node has some attributes that actually hold the data of the file. I need a very quick way to count the number of each type of element, (List and Note). Lists is simply the root and doesn't matter. I can do this with a simple string search or something similar, but I need to make this as fast as possible. Design Parameters: Must be in java (Android application). Must AVOID allocating memory as much as possible. Must return the total number of Note elements and the number of List elements in the file, regardless of location in file. Number of Lists will typically be small (1-4), and number of notes can potentially be very large (upwards of 1000, typically 100) per file. I look forward to your suggestions.

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  • Looping over commits for a file with jGit

    - by Andy Jarrett
    I've managed to get to grips with the basics of jGit file in terms of connecting to a repos and adding, commiting, and even looping of the commit messages for the files. File gitDir = new File("/Users/myname/Sites/helloworld/.git"); RepositoryBuilder builder = new RepositoryBuilder(); Repository repository; repository = builder.setGitDir(gitDir).readEnvironment() .findGitDir().build(); Git git = new Git(repository); RevWalk walk = new RevWalk(repository); RevCommit commit = null; // Add all files // AddCommand add = git.add(); // add.addFilepattern(".").call(); // Commit them // CommitCommand commit = git.commit(); // commit.setMessage("Commiting from java").call(); Iterable<RevCommit> logs = git.log().call(); Iterator<RevCommit> i = logs.iterator(); while (i.hasNext()) { commit = walk.parseCommit( i.next() ); System.out.println( commit.getFullMessage() ); } What I want to do next is be able to get all the commit message for a single file and then be able revert the single file back to a specific reference/point in time.

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  • What's the most efficient way to load data from a file to a collection on-demand?

    - by Dan
    I'm working on a java project that will allows users to parse multiple files with potentially thousands of lines. The information parsed will be stored in different objects, which then will be added to a collection. Since the GUI won't require to load ALL these objects at once and keep them in memory, I'm looking for an efficient way to load/unload data from files, so that data is only loaded into the collection when a user requests it. I'm just evaluation options right now. I've also thought of the case where, after loading a subset of the data into the collection, and presenting it on the GUI, the best way to reload the previously observed data. Re-run the parser/Populate collection/Populate GUI? or probably find a way to keep the collection into memory, or serialize/deserialize the collection itself? I know that loading/unloading subsets of data can get tricky if some sort of data filtering is performed. Let's say that I filter on ID, so my new subset will contain data from two previous analyzed subsets. This would be no problem is I keep a master copy of the whole data in memory. I've read that google-collections are good and efficient when handling big amounts of data, and offer methods that simplify lots of things so this might offer an alternative to allow me to keep the collection in memory. This is just general talking. The question on what collection to use is a separate and complex thing. Do you know what's the general recommendation on this type of task? I'd like to hear what you've done with similar scenarios. I can provide more specifics if needed.

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  • How can I solve the Log Pile wooden puzzle with a computer program?

    - by craig1410
    Can anyone suggest how to solve the Log Pile wooden puzzle using a computer program? See here to visualise the puzzle: http://www.puzzlethis.co.uk/products/madcow/the_log_pile.htm The picture only shows some of the pieces. The full set of 10 pieces are configured as follows with 1 representing a peg, -1 representing a hole and 0 representing neither a peg nor a hole. -1,1,0,-1,0 1,0,1,0,0 1,-1,1,0,0 -1,-1,0,0,-1 -1,1,0,1,0 0,1,0,0,1 1,0,-1,0,-1 0,-1,0,1,0 0,0,-1,1,-1 1,0,-1,0,0 The pieces can be interlocked in two layers of 5 pieces each with the top layer at 90 degrees to the bottom layer as shown in the above link. I have already created a solution to this problem myself using Java but I feel that it was a clumsy solution and I am interested to see some more sophisticated solutions. Feel free to either suggest a general approach or to provide a working program in the language of your choice. My approach was to use the numeric notation above to create an array of "Logs". I then used a combination/permutation generator to try all possible arrangements of the Logs until a solution was found where all the intersections equated to zero (ie. Peg to Hole, Hole to Peg or Blank to Blank). I used some speed-ups to detect the first failed intersection for a given permutation and move on to the next permutation. I hope you find this as interesting as I have. Thanks, Craig.

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