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  • Graph Tour with Uniform Cost Search in Java

    - by user324817
    Hi. I'm new to this site, so hopefully you guys don't mind helping a nub. Anyway, I've been asked to write code to find the shortest cost of a graph tour on a particular graph, whose details are read in from file. The graph is shown below: http://img339.imageshack.us/img339/8907/graphr.jpg This is for an Artificial Intelligence class, so I'm expected to use a decent enough search method (brute force has been allowed, but not for full marks). I've been reading, and I think that what I'm looking for is an A* search with constant heuristic value, which I believe is a uniform cost search. I'm having trouble wrapping my head around how to apply this in Java. Basically, here's what I have: Vertex class - ArrayList<Edge> adjacencies; String name; int costToThis; Edge class - final Vertex target; public final int weight; Now at the moment, I'm struggling to work out how to apply the uniform cost notion to my desired goal path. Basically I have to start on a particular node, visit all other nodes, and end on that same node, with the lowest cost. As I understand it, I could use a PriorityQueue to store all of my travelled paths, but I can't wrap my head around how I show the goal state as the starting node with all other nodes visited. Here's what I have so far, which is pretty far off the mark: public static void visitNode(Vertex vertex) { ArrayList<Edge> firstEdges = vertex.getAdjacencies(); for(Edge e : firstEdges) { e.target.costToThis = e.weight + vertex.costToThis; queue.add(e.target); } Vertex next = queue.remove(); visitNode(next); } Initially this takes the starting node, then recursively visits the first node in the PriorityQueue (the path with the next lowest cost). My problem is basically, how do I stop my program from following a path specified in the queue if that path is at the goal state? The queue currently stores Vertex objects, but in my mind this isn't going to work as I can't store whether other vertices have been visited inside a Vertex object. Help is much appreciated! Josh

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  • refactoring this function in Java

    - by Joel
    Hi folks, I'm learning Java, and I know one of the big complaints about newbie programmers is that we make really long and involved methods that should be broken into several. Well here is one I wrote and is a perfect example. :-D. public void buildBall(){ /* sets the x and y value for the center of the canvas */ double i = ((getWidth() / 2)); double j = ((getHeight() / 2)); /* randomizes the start speed of the ball */ vy = 3.0; vx = rgen.nextDouble(1.0, 3.0); if (rgen.nextBoolean(.05)) vx = -vx; /* creates the ball */ GOval ball = new GOval(i,j,(2 *BALL_RADIUS),(2 * BALL_RADIUS)); ball.setFilled(true); ball.setFillColor(Color.RED); add(ball); /* animates the ball */ while(true){ i = (i + (vx* 2)); j = (j + (vy* 2)); if (i > APPLICATION_WIDTH-(2 * BALL_RADIUS)){ vx = -vx; } if (j > APPLICATION_HEIGHT-(2 * BALL_RADIUS)){ vy = -vy; } if (i < 0){ vx = -vx; } if (j < 0){ vy = -vy; } ball.move(vx + vx, vy + vy); pause(10); /* checks the edges of the ball to see if it hits an object */ colider = getElementAt(i, j); if (colider == null){ colider = getElementAt(i + (2*BALL_RADIUS), j); } if (colider == null){ colider = getElementAt(i + (2*BALL_RADIUS), j + (2*BALL_RADIUS)); } if (colider == null){ colider = getElementAt(i, j + (2*BALL_RADIUS)); } /* If the ball hits an object it reverses direction */ if (colider != null){ vy = -vy; /* removes bricks when hit but not the paddle */ if (j < (getHeight() -(PADDLE_Y_OFFSET + PADDLE_HEIGHT))){ remove(colider); } } } You can see from the title of the method that I started with good intentions of "building the ball". There are a few issues I ran up against: The problem is that then I needed to move the ball, so I created that while loop. I don't see any other way to do that other than just keep it "true", so that means any other code I create below this loop won't happen. I didn't make the while loop a different function because I was using those variables i and j. So I don't see how I can refactor beyond this loop. So my main question is: How would I pass the values of i and j to a new method: "animateBall" and how would I use ball.move(vx + vx, vy + vy); in that new method if ball has been declared in the buildBall method? I understand this is probably a simple thing of better understanding variable scope and passing arguments, but I'm not quite there yet...

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  • What is this weird script I found on facebook?

    - by Mike Turley
    Not so much a question to help my own programming, but I found this page on facebook with a cool illusion and a page that says "to see the real illusion, copy and paste this code into your address bar" and there is a script: http://pastebin.com/LQUVQ8hm What the hell is this? What would happen if I put it in my address bar, which I assume would be a very unwise idea? I am confused.

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  • Customs toString in Java not giving desired output and throwing error

    - by user2972048
    I am writing a program in Java to accept and validate dates according to the Gregorian Calendar. My public boolean setDate(String aDate) function for an incorrect entry is suppose to change the boolean goodDate variable to false. That variable is suppose tell the toString function, when called, to output "Invalid Entry" but it does not. My public boolean setDate(int d, int m, int y) function works fine though. I've only included the problem parts as its a long piece of code. Thanks public boolean setDate(int day, int month, int year){ // If 1 <= day <= 31, 1 <= month <= 12, and 0 <= year <= 9999 & the day match with the month // then set object to this date and return true // Otherwise,return false (and do nothing) boolean correct = isTrueDate(day, month, year); if(correct){ this.day = day; this.month = month; this.year = year; return true; }else{ goodDate = false; return false; } //return false; } public boolean setDate(String aDate){ // If aDate is of the form "dd/mm/yyyy" or "d/mm/yyyy" // Then set the object to this date and return true. // Otherwise, return false (and do nothing) Date d = new Date(aDate); boolean correct = isTrueDate(d.day, d.month, d.year); if(correct){ this.day = d.day; this.month = d.month; this.year = d.year; return true; }else{ goodDate = false; return false; } } public String toString(){ // outputs a String of the form "dd/mm/yyyy" // where dd must be 2 digits (with leading zero if needed) // mm must be 2 digits (with leading zero if needed) // yyyy must be 4 digits (with leading zeros if needed) String day1; String month1; String year1; if(day<10){ day1 = "0" + Integer.toString(this.day); } else{ day1 = Integer.toString(this.day); } if(month<10){ month1 = "0" + Integer.toString(this.month); } else{ month1 = Integer.toString(this.month); } if(year<10){ year1 = "00" + Integer.toString(this.year); } else{ year1 = Integer.toString(this.year); } if(goodDate){ return day1 +"/" +month1 +"/" + year1; }else{ goodDate = true; return "Invalid Entry"; } } Thank you

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  • Java array of arry [matrix] of an integer partition with fixed term

    - by user335209
    Hello, for my study purpose I need to build an array of array filled with the partitions of an integer with fixed term. That is given an integer, suppose 10 and given the fixed number of terms, suppose 5 I need to populate an array like this 10 0 0 0 0 9 0 0 0 1 8 0 0 0 2 7 0 0 0 3 ............ 9 0 0 1 0 8 0 0 1 1 ............. 7 0 1 1 0 6 0 1 1 1 ............ ........... 0 6 1 1 1 ............. 0 0 0 0 10 am pretty new to Java and am getting confused with all the for loops. Right now my code can do the partition of the integer but unfortunately it is not with fixed term public class Partition { private static int[] riga; private static void printPartition(int[] p, int n) { for (int i= 0; i < n; i++) System.out.print(p[i]+" "); System.out.println(); } private static void partition(int[] p, int n, int m, int i) { if (n == 0) printPartition(p, i); else for (int k= m; k > 0; k--) { p[i]= k; partition(p, n-k, n-k, i+1); } } public static void main(String[] args) { riga = new int[6]; for(int i = 0; i<riga.length; i++){ riga[i] = 0; } partition(riga, 6, 1, 0); } } the output I get it from is like this: 1 5 1 4 1 1 3 2 1 3 1 1 1 2 3 1 2 2 1 1 2 1 2 1 2 1 1 1 what i'm actually trying to understand how to proceed is to have it with a fixed terms which would be the columns of my array. So, am stuck with trying to get a way to make it less dynamic. Any help?

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  • Java issues with Apache 2.0 Agent 2.202 for RHEL5 Linux 64bit

    - by Richard
    In trying to install Apache 2.0 Agent 2.202 for RHEL5 Linux 64bit, the dialogue appears as follows. $ ./setup Error : java is not present in path. Please enter JAVAHOME path to pick up java:/usr/lib/jvm/java-1.6.0-openjdk-1.6.0.0.x86_64/jre/ Launching installer... Attach to native process failed $ ./setup Error : java is not present in path. Please enter JAVAHOME path to pick up java:/usr/lib/jvm/java-1.6.0-openjdk-1.6.0.0.x86_64/jre/lib ./setup: line 80: [: 107:: integer expression expected ./setup: line 83: [: 107:: integer expression expected Error : Incorrect java version (1.2.2 or above is needed). Please enter JAVAHOME path to pick up java: On the server we have the following JREs and I've tried both. $ sudo rpm -qa | egrep "(openjdk|icedtea)" java-1.6.0-openjdk-1.6.0.0-1.27.1.10.8.el5_8 $ find 2>/dev/null | grep -i '/jre/' ./usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre/bin/ ... ./usr/lib/jvm/java-1.6.0-openjdk-1.6.0.0.x86_64/jre/ Any suggestions? I know I'm overlooking something. In previous searches I've only found one other posting that comes close but it has no responses (http://forum.parallels.com/showthread.php?t=76556).

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  • JavaOne Tutorial Report - JavaFX 2 – A Java Developer’s Guide

    - by Janice J. Heiss
    Oracle Java Technology Evangelist Stephen Chin and Independent Consultant Peter Pilgrim presented a tutorial session intended to help developers get a handle on JavaFX 2. Stephen Chin, a Java Champion, is co-author of the Pro JavaFX Platform 2, while Java Champion Peter Pilgrim is an independent consultant who works out of London.NightHacking with Stephen ChinBefore discussing the tutorial, a note about Chin’s “NightHacking Tour,” wherein from 10/29/12 to 11/11/12, he will be traveling across Europe via motorcycle stopping at JUGs and interviewing Java developers and offering live video streaming of the journey. As he says, “Along the way, I will visit user groups, interviewing interesting folks, and hack on open source projects. The last stop will be the Devoxx conference in Belgium.”It’s a dirty job but someone’s got to do it. His trip will take him from the UK through the Netherlands, Germany, Switzerland, Italy, France, and finally to Devoxx in Belgium. He has interviews lined up with Ben Evans, Trisha Gee, Stephen Coulebourne, Martijn Verburg, Simon Ritter, Bert Ertman, Tony Epple, Adam Bien, Michael Hutterman, Sven Reimers, Andres Almiray, Gerrit Grunewald, Bertrand Boetzmann, Luc Duponcheel, Stephen Janssen, Cheryl Miller, and Andrew Phillips. If you expect to be in Chin’s vicinity at the end of October and in early November, by all means get in touch with him at his site and add your perspective. The more the merrier! Taking the JavaFX PlungeNow to the business at hand. The “JavaFX 2 – A Java Developer’s Guide” tutorial introduced Java developers to the JavaFX 2 platform from the perspective of seasoned Java developers. It demonstrated the breadth of the JavaFX APIs through examples that are built out in the course of the session in an effort to present the basic requirements in using JavaFX to build rich internet applications. Chin began with a quote from Oracle’s Christopher Oliver, the creator of F3, the original version of JavaFX, on the importance of GUIs:“At the end of the day, on the one hand we have computer systems, and on the other, people. Connecting them together, and allowing people to interact with computer systems in a compelling way, requires graphical user interfaces.”Chin explained that JavaFX is about producing an immersive application experience that involves cross-platform animation, video and charting. It can integrate Java, JavaScript and HTML in the same application. The new graphics stack takes advantage of hardware acceleration for 2D and 3D applications. In addition, we can integrate Swing applications using JFXPanel.He reminded attendees that they were building JavaFX apps using pure Java APIs that included builders for declarative construction; in addition, alternative languages can be used for simpler UI creation. In addition, developers can call upon alternative languages such as GroovyFX, ScalaFX and Visage, if they want simpler UI creation. He presented the fundamentals of JavaFX 2.0: properties, lists and binding and then explored primitive, object and FX list collection properties. Properties in JavaFX are observable, lazy and type safe. He then provided an example of property declaration in code.  Pilgrim and Chin explained the architectural structure of JavaFX 2 and its basic properties:JavaFX 2.0 properties – Primitive, Object, and FX List Collection properties. * Primitive Properties* Object Properties* FX List Collection Properties* Properties are:– Observable– Lazy– Type SafeChin and Pilgrim then took attendees through several participatory demos and got deep into the weeds of the code for the two-hour session. At the end, everyone knew a lot more about the inner workings of JavaFX 2.0.

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  • Building a Store Locator ASP.NET Application Using Google Maps API (Part 3)

    Over the past two weeks I've showed how to build a store locator application using ASP.NET and the free Google Maps API and Google's geocoding service. Part 1 looked at creating the database to record the store locations. This database contains a table named Stores with columns capturing each store's address and latitude and longitude coordinates. Part 1 also showed how to use Google's geocoding service to translate a user-entered address into latitude and longitude coordinates, which could then be used to retrieve and display those stores within (roughly) a 15 mile area. At the end of Part 1, the results page listed the nearby stores in a grid. In Part 2 we used the Google Maps API to add an interactive map to the search results page, with each nearby store displayed on the map as a marker. The map added in Part 2 certainly improves the search results page, but the way the nearby stores are displayed on the map leaves a bit to be desired. For starters, each nearby store is displayed on the map using the same marker icon, namely a red pushpin. This makes it difficult to match up the nearby stores listed in the grid with those displayed on the map. Hovering the mouse over a marker on the map displays the store number in a tooltip, but ideally a user could click a marker to see more detailed information about the store, such as its address, phone number, a photo of the storefront, and so forth. This third and final installment shows how to enhance the map created in Part 2. Specifically, we'll see how to customize the marker icons displayed in the map to make it easier to identify which marker corresponds to which nearby store location. We'll also look at adding rich popup windows to each marker, which includes detailed store information and can be updated further to include pictures and other HTML content. Read on to learn more! Read More >

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  • Building a Store Locator ASP.NET Application Using Google Maps API (Part 3)

    Over the past two weeks I've showed how to build a store locator application using ASP.NET and the free Google Maps API and Google's geocoding service. Part 1 looked at creating the database to record the store locations. This database contains a table named Stores with columns capturing each store's address and latitude and longitude coordinates. Part 1 also showed how to use Google's geocoding service to translate a user-entered address into latitude and longitude coordinates, which could then be used to retrieve and display those stores within (roughly) a 15 mile area. At the end of Part 1, the results page listed the nearby stores in a grid. In Part 2 we used the Google Maps API to add an interactive map to the search results page, with each nearby store displayed on the map as a marker. The map added in Part 2 certainly improves the search results page, but the way the nearby stores are displayed on the map leaves a bit to be desired. For starters, each nearby store is displayed on the map using the same marker icon, namely a red pushpin. This makes it difficult to match up the nearby stores listed in the grid with those displayed on the map. Hovering the mouse over a marker on the map displays the store number in a tooltip, but ideally a user could click a marker to see more detailed information about the store, such as its address, phone number, a photo of the storefront, and so forth. This third and final installment shows how to enhance the map created in Part 2. Specifically, we'll see how to customize the marker icons displayed in the map to make it easier to identify which marker corresponds to which nearby store location. We'll also look at adding rich popup windows to each marker, which includes detailed store information and can be updated further to include pictures and other HTML content. Read on to learn more! Read More >Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Great Free Courses on Building HTML5 apps using ASP.NET Web API, Knockout.js and jQuery

    - by ScottGu
    Pluralsight has developed some great training courses on the new .NET 4.5 and VS 2012 release, including two fantastic courses from John Papa that cover how to build HTML5 web apps using ASP.NET Web API, Knockout and jQuery: Single Page Apps with HTML5, Web API, Knockout and jQuery Building HTML5 and JavaScript Apps with MVVM and Knockout Free 1-Month Subscription to the Courses Pluralsight is offering a special promotion that allows you to get a free 1-month subscription to watch the above courses at no cost.  There is no obligation to buy anything at the end of the offer and you don’t need to supply a credit card in order to take part in it. To get access to the course you simply follow @pluralsight and @john_papa on Twitter and then visit this page and enter your Twitter name using the form on it.  Pluralsight will then send you a private twitter message containing the access code that you can use to subscribe to the courses (and download the course exercise files).  Once you are subscribed to the course you have one month to watch the course (and you can watch it as many times as you want during the month). Pluralsight is running the promotion through Sept 18th – so sign-up now to get access.  Once you are signed up you then have a month to watch the course. Hope this helps, Scott P.S. And if you are new to Twitter you can also optionally follow me: @scottgu

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  • java.lang.RuntimeException: Unable to start activity ComponentInfo cannot be cast to android.widget.ZoomControls

    - by Hwl
    I'm new to android development, hope you all can help me. I got this androidVNC viewer source code from internet. When i'm running the androidVNC application in the emulator, it will exit automatically then i get following errors in LogCat. Can anyone one help me? Thanks. FATAL EXCEPTION: main java.lang.RuntimeException: Unable to start activity ComponentInfo{android.androidVNC/android.androidVNC.VncCanvasActivity}: java.lang.ClassCastException: com.antlersoft.android.zoomer.ZoomControls cannot be cast to android.widget.ZoomControls at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980) at android.app.ActivityThread.access$600(ActivityThread.java:122) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:4340) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.ClassCastException: com.antlersoft.android.zoomer.ZoomControls cannot be cast to android.widget.ZoomControls at android.androidVNC.VncCanvasActivity.onCreate(VncCanvasActivity.java:585) at android.app.Activity.performCreate(Activity.java:4465) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919) ... 11 more This is the ZoomControls java file: package com.antlersoft.android.zoomer; import android.content.Context; import android.util.AttributeSet; import android.view.LayoutInflater; import android.view.MotionEvent; import android.view.View; import android.view.animation.AlphaAnimation; import android.widget.ImageButton; import android.widget.LinearLayout; import android.widget.ZoomButton; public class ZoomControls extends LinearLayout { private final ZoomButton mZoomIn; private final ZoomButton mZoomOut; private final ImageButton mZoomKeyboard; public ZoomControls(Context context) { this(context, null); } public ZoomControls(Context context, AttributeSet attrs) { super(context, attrs); setFocusable(false); LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); inflater.inflate(R.layout.zoom_controls, this, // we are the parent true); mZoomIn = (ZoomButton) findViewById(R.id.zoomIn); mZoomOut = (ZoomButton) findViewById(R.id.zoomOut); mZoomKeyboard = (ImageButton) findViewById(R.id.zoomKeys); } public void setOnZoomInClickListener(OnClickListener listener) { mZoomIn.setOnClickListener(listener); } public void setOnZoomOutClickListener(OnClickListener listener) { mZoomOut.setOnClickListener(listener); } public void setOnZoomKeyboardClickListener(OnClickListener listener) { mZoomKeyboard.setOnClickListener(listener); } /* * Sets how fast you get zoom events when the user holds down the * zoom in/out buttons. */ public void setZoomSpeed(long speed) { mZoomIn.setZoomSpeed(speed); mZoomOut.setZoomSpeed(speed); } @Override public boolean onTouchEvent(MotionEvent event) { /* Consume all touch events so they don't get dispatched to the view * beneath this view. */ return true; } public void show() { fade(View.VISIBLE, 0.0f, 1.0f); } public void hide() { fade(View.GONE, 1.0f, 0.0f); } private void fade(int visibility, float startAlpha, float endAlpha) { AlphaAnimation anim = new AlphaAnimation(startAlpha, endAlpha); anim.setDuration(500); startAnimation(anim); setVisibility(visibility); } public void setIsZoomInEnabled(boolean isEnabled) { mZoomIn.setEnabled(isEnabled); } public void setIsZoomOutEnabled(boolean isEnabled) { mZoomOut.setEnabled(isEnabled); } @Override public boolean hasFocus() { return mZoomIn.hasFocus() || mZoomOut.hasFocus(); } } This is the zoom_controls XML file: <merge xmlns:android="http://schemas.android.com/apk/res/android"> <ZoomButton android:id="@+id/zoomOut" android:background="@drawable/btn_zoom_down" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <ImageButton android:id="@+id/zoomKeys" android:background="@android:drawable/ic_dialog_dialer" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <ZoomButton android:id="@+id/zoomIn" android:background="@drawable/btn_zoom_up" android:layout_width="wrap_content" android:layout_height="wrap_content" /> </merge>

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  • How to enable services Discovery API in GoogleCL?

    - by Marcos
    There are bits and pieces of information all over the place but I'm trying to put it all together so that GoogleCL finally accesses more than the initial 7 services. Does anyone know of a step-by-step? Right now any attempt outside these result in the error message: google tasks list Did you specify the service correctly? Must be one of 'picasa', 'blogger', 'youtube', 'docs', 'contacts', 'calendar', 'finance' I installed GoogleCL from the Ubuntu repos, authenticated a few bundled services like contacts, docs etc. and those work great, giving me access to do certain operations like upload from the command line. I would really like to get it going to support tasks and all the other elegible Google services shown at https://code.google.com/apis/explorer/#_s=tasks Here are some guides/partial steps I've found: http://code.google.com/p/googlecl/wiki/DiscoveryManual (indicates needing to check it out updated GoogleCL from the subversion repository.) http://code.google.com/p/google-api-python-client/wiki/Installation easy_install --upgrade google-api-python-client http://code.google.com/p/googlecl/wiki/Install http://code.google.com/p/googlecl/source/checkout sudo -i cd /usr/local/src/ svn checkout http://googlecl.googlecode.com/svn/trunk/ googlecl-read-only cat googlecl-read-only/INSTALL.txt cd /usr/local/src/googlecl-read-only/ python setup.py install Result: $ google discovery list Traceback (most recent call last): File "/usr/bin/google", line 488, in run_interactive run_once(options, args) File "/usr/bin/google", line 540, in run_once options.config) File "/usr/bin/google", line 364, in import_service force_gdata_v1 = config.lazy_get(package.SECTION_HEADER, AttributeError: 'module' object has no attribute 'SECTION_HEADER'

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  • Handling SEO for Infinite pages that cause external slow API calls

    - by Noam
    I have an 'infinite' amount of pages in my site which rely on an external API. Generating each page takes time (1 minute). Links in the site point to such pages, and when a users clicks them they are generated and he waits. Considering I cannot pre-create them all, I am trying to figure out the best SEO approach to handle these pages. Options: Create really simple pages for the web spiders and only real users will fetch the data and generate the page. A little bit 'afraid' google will see this as low quality content, which might also feel duplicated. Put them under a directory in my site (e.g. /non-generated/) and put a disallow in robots.txt. Problem here is I don't want users to have to deal with a different URL when wanting to share this page or make sense of it. Thought about maybe redirecting real users from this URL back to the regular hierarchy and that way 'fooling' google not to get to them. Again not sure he will like me for that. Letting him crawl these pages. Main problem is I can't control to rate of the API calls and also my site seems slower than it should from a spider's perspective (if he only crawled the generated pages, he'd think it's much faster). Which approach would you suggest?

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  • How to get initial API right using TDD?

    - by Vytautas Mackonis
    This might be a rather silly question as I am at my first attempts at TDD. I loved the sense of confidence it brings and generally better structure of my code but when I started to apply it on something bigger than one-class toy examples, I ran into difficulties. Suppose, you are writing a library of sorts. You know what it has to do, you know a general way of how it is supposed to be implemented (architecture wise), but you keep "discovering" that you need to make changes to your public API as you code. Perhaps you need to transform this private method into strategy pattern (and now need to pass a mocked strategy in your tests), perhaps you misplaced a responsibility here and there and split an existing class. When you are improving upon existing code, TDD seems a really good fit, but when you are writing everything from scratch, the API you write tests for is a bit "blurry" unless you do a big design up front. What do you do when you already have 30 tests on the method that had its signature (and for that part, behavior) changed? That is a lot of tests to change once they add up.

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  • Using Coherence API to get POF bytes

    - by Bruno.Borges
    Someone raised the question on how to use the Coherence API to get the bytes of an object in POF (Portable Object Format) programatically. So I came up with this small code that shows the very cool API simple usage :-)   SimplePofContext spc = new SimplePofContext();    spc.registerUserType(0, User.class, new UserSerializer());    // consider UserSerializer as an implementation of PofSerializer            User u = new User();    u.setId(21);    u.setName("Some Name");    u.setEmail("[email protected]");            ByteArrayOutputStream baos = new ByteArrayOutputStream();    DataOutput dataOutput = new DataOutputStream(baos);    BufferOutput bufferOutput = new WrapperBufferOutput(dataOutput);    spc.serialize(bufferOutput, u);            byte[] byteArray = baos.toByteArray();    System.out.println(Arrays.toString(byteArray));  Easy, isn't?

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  • Authenticate native mobile app using a REST API

    - by Supercell
    I'm starting a new project soon, which is targeting mobile application for all major mobile platforms (iOS, Android, Windows). It will be a client-server architecture. The app is both informational and transactional. For the transactional part, they're required to have an account and log in before a transaction can be made. I'm new to mobile development, so I don't know how the authentication part is done on these platforms. The clients will communicate with the server through a REST API. Will be using HTTPS ofcourse. I haven't yet decided if I want the user to log in when they open the app, or only when they perform a transaction. I got the following questions: 1) Like the Facebook application, you only enter your credentials when you open the application for the first time. After that, you're automatically signed in every time you open the app. How does one accomplish this? Just simply by encrypting and storing the credentials on the device and sending them every time the app starts? 2) Do I need to authenticate the user for each (transactional) request made to the REST API or use a token based approach? Please feel free to suggest other ways for authentication. Thanks!

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  • Google Currency Convertor JSON API

    - by Gopinath
    There are many live currency conversion services available on the web and the popular one’s among them are – Google, Yahoo, MSN & XE. Among all these four Google is the developer’s darling and it provides a simple JSON API that can be integrated in your applications.  http://www.google.com/ig/calculator?hl=en&q=1USD=?INR Using the API is very simple and it takes two parameters as input. The first parameter “hl” is the language code in which you want output. The second parameter “q” is the conversion query in the format <number><from currency code>=?<to currency code>. In the URL give above the query requests for conversion of 1 USD in INR. JSON output for the above query would be  similar to {lhs: "1 U.S. dollar",rhs: "54.4602984 Indian rupees",error: "",icc: true} Examples: 100 USD in INR  http://www.google.com/ig/calculator?hl=en&q=100USD=?INR Example 2: 1 GBP in INR http://www.google.com/ig/calculator?hl=en&q=1GBP=?INR Example 3: 1 USD in INR, output the data in French language http://www.google.com/ig/calculator?hl=fr&q=1USD=?INR   This is an undocumented service and expect changes at any time. But as long as it works, you got a programmatic way to convert currencies.

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  • Good JDBC pattern

    - by Java Developer
    What is the good practice for database operation in Java application? Do you construct the DML syntax in the Java code and send the statements to DB engine for execution, or you just collect the parameters and then make a call to stored procedure with the parameters via java code? or neither because that's just not how to do it? can anyone give an example of a full database utility classes to do database operations in Java app? also what about the transaction manager? My assignment is to make database operation that is modular in Java. Thanks

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  • Java: micro-optimizing array manipulation

    - by Martin Wiboe
    Hello all, I am trying to make a Java port of a simple feed-forward neural network. This obviously involves lots of numeric calculations, so I am trying to optimize my central loop as much as possible. The results should be correct within the limits of the float data type. My current code looks as follows (error handling & initialization removed): /** * Simple implementation of a feedforward neural network. The network supports * including a bias neuron with a constant output of 1.0 and weighted synapses * to hidden and output layers. * * @author Martin Wiboe */ public class FeedForwardNetwork { private final int outputNeurons; // No of neurons in output layer private final int inputNeurons; // No of neurons in input layer private int largestLayerNeurons; // No of neurons in largest layer private final int numberLayers; // No of layers private final int[] neuronCounts; // Neuron count in each layer, 0 is input // layer. private final float[][][] fWeights; // Weights between neurons. // fWeight[fromLayer][fromNeuron][toNeuron] // is the weight from fromNeuron in // fromLayer to toNeuron in layer // fromLayer+1. private float[][] neuronOutput; // Temporary storage of output from previous layer public float[] compute(float[] input) { // Copy input values to input layer output for (int i = 0; i < inputNeurons; i++) { neuronOutput[0][i] = input[i]; } // Loop through layers for (int layer = 1; layer < numberLayers; layer++) { // Loop over neurons in the layer and determine weighted input sum for (int neuron = 0; neuron < neuronCounts[layer]; neuron++) { // Bias neuron is the last neuron in the previous layer int biasNeuron = neuronCounts[layer - 1]; // Get weighted input from bias neuron - output is always 1.0 float activation = 1.0F * fWeights[layer - 1][biasNeuron][neuron]; // Get weighted inputs from rest of neurons in previous layer for (int inputNeuron = 0; inputNeuron < biasNeuron; inputNeuron++) { activation += neuronOutput[layer-1][inputNeuron] * fWeights[layer - 1][inputNeuron][neuron]; } // Store neuron output for next round of computation neuronOutput[layer][neuron] = sigmoid(activation); } } // Return output from network = output from last layer float[] result = new float[outputNeurons]; for (int i = 0; i < outputNeurons; i++) result[i] = neuronOutput[numberLayers - 1][i]; return result; } private final static float sigmoid(final float input) { return (float) (1.0F / (1.0F + Math.exp(-1.0F * input))); } } I am running the JVM with the -server option, and as of now my code is between 25% and 50% slower than similar C code. What can I do to improve this situation? Thank you, Martin Wiboe

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