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• Set up Java path for terminal

  - by Xsteen

  Trying to set up a path for the terminal. I already have Eclipse running great. Dual os between windows 7 and Ubuntu 12.04. However, I would prefer to run everything out of Ubuntu, just not very experienced and all the forums I have searched are not giving me the step by step answers I need to make this happen. I included a screen shot of some information about my version etc. Any help would be greatly appreciated at this point I've put 10+ hours into this and this is my last resort.

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• any refresher courses on java enterprise [on hold]

  - by f1wade

  hi can anyone surggest anywhere or any online material, that will serve as a short (1 day) course to cover the basics of spring, hibernate, webflow, richfaces, jsf, beans I am trying to find one that just covers the basics, (how to create this, this and this, and heres another way, these are the options) kind of course. i'm looking for something more point blank, and quick, something i can jot down notes, and then use them back at my application code base. can anyone suggest anywhere, online, or local to nottingham / derby / leicester, UK please.

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• Java - What methods to put in an interface and what to keep out

  - by lewicki

  I'm designing a file handler interface: public interface FileHandler { public void openFileHandler(String fileName); public void closeFileHandler(); public String readLine(); public String [] parseLine(String line); public String [] checkLine(String line[]); public void incrementLineCount(); public void incrementLineSuccessCount(); public void incrementLineErrorCount(); public int getLineCount(); public int getLineSuccessCount(); public int getLineErrorCount(); } It is soon apparent to me that these methods can't be made private. I don't want incrementLineCount to be public. What is proper way to design an interface like this?

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• Question about JPanel "transition" for Java Swing

  - by user16778

  I want to make like a sort of main menu (in GUI). When the user clicks the start button, the screen transition into another "screen" (JPanel). This image will make it easier to understand. http://i.imgur.com/Cfdry.png Currently, I have a MainMenu extends JPanel and that gets added into a driver class with a JFrame. I can't figure how to switch to another class like Game extends JPanel. So when the user clicks the start button in MainMenu, I want it to somehow hide itself and the Game to show itself. Thanks.

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• How should I load level data in java?

  - by Matthew G.

  I'm setting up my engine for a certain action/arcade game to have a set of commands that would look something like this. Set landscape to grass Create rocks at ... Create player at X, Y Set goal to "Get to point X Y" Spawn enemy at X, Y I'd then have each object knowing what it has to do, and acting on its own. I've been thinking about how to store this data. External data files could be parsed by a level class, and certain objects can be spawned through that. I could also create a base level class and extend it for each level, but that'd create a large amount of classes. Another idea is to have one level parser class, but have a case for each level. This would be extremely silly and bulky, but I mention it because I found that I did this at 2 AM last night. I'm finally getting why I have to plan out my inheritances, though. RIP project. I might be completely missing another option.

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• Új dimenzió middleware (Java) virtualizáció területén

  - by peter.nagy

  Korábban már írtam róla, de most megtörtént a hivatalos bejelentés. Tehát elérheto lesz a JRockit Virtual Edition ami várhatóan új mértéket teremt middleware területen. Továbbá megjelent a Virtual Assembly Builder mely a rohamosan terjedo virtualizációs környezetben használt konfiguráció menedzsmentjét támogatja hatékonyan. A termék elso nyilvános webcast-jára pedig itt tessék regisztrálni.

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• Java enum pairs / "subenum" or what exactly?

  - by vemalsar

  I have an RPG-style Item class and I stored the type of the item in enum (itemType.sword). I want to store subtype too (itemSubtype.long), but I want to express the relation between two data type (sword can be long, short etc. but shield can't be long or short, only round, tower etc). I know this is wrong source code but similar what I want: enum type { sword; } //not valid code! enum swordSubtype extends type.sword { short, long } Question: How can I define this connection between two data type (or more exactly: two value of the data types), what is the most simple and standard way? Array-like data with all valid (itemType,itemSubtype) enum pairs or (itemType,itemSubtype[]) so more subtype for one type, it would be the best. OK but how can I construct this simplest way? Special enum with "subenum" set or second level enum or anything else if it does exists 2 dimensional "canBePairs" array, itemType and itemSubtype dimensions with all type and subtype and boolean elements, "true" means itemType (first dimension) and itemSubtype (second dimension) are okay, "false" means not okay Other better idea Thank you very much!

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• Simple algorithm for a sudoku solver java

  - by user142050

  just a quick note first, I originally asked this question on stack overflow but was refered here instead. I've been stuck on this thing for a while, I just can't wrap my head around it. For a homework, I have to produce an algorithm for a sudoku solver that can check what number goes in a blank square in a row, in a column and in a block. It's a regular 9x9 sudoku and I'm assuming that the grid is already printed so I have to produce the part where it solves it. I've read a ton of stuff on the subject I just get stuck expressing it. I want the solver to do the following: If the value is smaller than 9, increase it by 1 If the value is 9, set it to zero and go back 1 If the value is invalid, increase by 1 I've already read about backtracking and such but I'm in the early stage of the class so I'd like to keep it as simple as possible. I'm more capable of writing in pseudo code but not so much with the algorithm itself and it's the algorithm that is needed for this exercise. Thanks in advance for your help guys.

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• JAVA - multirow array

  - by user51447

  Here is my situation: a company has x number of employees and x number of machines. When someone is sick, the program have to give the best possible solution of people on the machines. But the employees can't work on every machine. I need a code for making little groups of possible solutions. this is a static example private int[][] arrayCompetenties={{0,0,1,0,1},{1,0,1,0,1},{1,1,0,0,1},{1,1,1,1,1},{0,0,0,0,1}}; = row is for the people and columns are for machines m1 m2 m3 m4 m5 m6 m7 p1 1 1 p2 1 1 1 1 p3 1 1 1 p4 1 1 1 p5 1 1 1 1 p6 1 1 1 1 p7 1 1 1 1 1 1 my question = with what code do i connect all the people to machine in groups (all the posibilities) like: p1 - m1 , p2-m2 , p3 - m3 , p4-m4 , p5 - m5 , p6-m6 p1 - m1 , p2-m3 , p3 - m3 , p4-m4 , p5 - m5 , p6-m6 p1 - m1 , p2-m4 , p3 - m5 , p4-m4 , p5 - m5 , p6-m6 p1 - m1 , p2-m5 , p3 - m3 , p4-m4 , p5 - m5 , p6-m6 p1 - m1 , p2-m2 , p3 - m3 , p4-m4 , p5 - m5 , p6-m6 .... i need a loop buth how? =D thanks!

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• Java Slick2d - Mouse picking how to take into account camera

  - by Corey

  When I move it it obviously changes the viewport so my mouse picking is off. My camera is just a float x and y and I use g.translate(-cam.cameraX+400, -cam.cameraY+300); to translate the graphics. I have the numbers hard coded just for testing purposes. How would I take into account the camera so my mouse picking works correctly. double mousetileX = Math.floor((double)mouseX/tiles.tileWidth); double mousetileY = Math.floor((double)mouseY/tiles.tileHeight); double playertileX = Math.floor(playerX/tiles.tileWidth); double playertileY = Math.floor(playerY/tiles.tileHeight); double lengthX = Math.abs((float)playertileX - mousetileX); double lengthY = Math.abs((float)playertileY - mousetileY); double distance = Math.sqrt((lengthX*lengthX)+(lengthY*lengthY)); if(input.isMousePressed(Input.MOUSE_LEFT_BUTTON) && distance < 4) { if(tiles.map[(int)mousetileX][(int)mousetileY] == 1) { tiles.map[(int)mousetileX][(int)mousetileY] = 0; } } That is my mouse picking code

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• Index Check and Correct Character Display in a Console Hangman Game for Java

  - by Jen

  I have this problem wherein, I can not display the correct characters given by the character. Here's what I meant: String words, in; String replaced_words; Scanner s = new Scanner (System.in); System.out.println("Enter a line of words basing on an event, verse, place or a name of a person."); words = s.nextLine(); System.out.println("The words you just placed are now accepted."); //using char array method, we tried to place the words into a characters array. char [] c = words.toCharArray(); // we need to replace the replaced_words = words.replace(' ', '_').replaceAll("[^\\-]", "-"); for (int i = 0; i < replaced_words.length(); i++) { System.out.print(replaced_words.charAt(i) + " "); } System.out.println("Now, please input a character, guessing the words you just placed."); in = s.nextLine(); in that code, want that the user, when types a word (or should it be character?), any of the correct character the user inputs will be displayed, and changes the hyphen to it...(more like the hangman series of games). How can I achieve this?

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• String Conversion to Char for Java Game

  - by Jen

  Is there someone who could help me achieve the following points on this problems? I can't seem to get it. I tried using toCharArray and Scanner to achieve this, but it doesn't work, nor do I know how to make this things possible for my word game. :( · Get a popular name of person, place, verse, saying or event from the user. This may have a single or multiple words in it. · Create a copy of this string to an array where each letter is replaced with a hyphen (-) and each space is replaced with an underscore (_). Symbols and numbers will remain shown. · The program then asks a letter from the user. If the letter is in the inputted string, then it should be shown on the array at the same position it is shown in the string. Meaning, the letter replaces the hyphen (-) at the correct position of the array. · The program again prompts for a letter from the user and replaces the hyphen (-) of the array if it exists on the inputted string. This will be repeatedly done until such time each hyphen (-) is replaced with the correct letter. · If the user inputs an invalid letter, that is, a letter that does not exist on the inputted string, then the program should inform the user. If this happens 3 times while there is still at least one hyphen on the array, then the program should inform the user that he lost the game and showing him the whole correct string. · If the user completes the game, meaning, all hyphens have been replaced with the correct letters; then the program should congratulate the user for a job well done.

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• Efficient way to render tile-based map in Java

  - by Lucius

  Some time ago I posted here because I was having some memory issues with a game I'm working on. That has been pretty much solved thanks to some suggestions here, so I decided to come back with another problem I'm having. Basically, I feel that too much of the CPU is being used when rendering the map. I have a Core i5-2500 processor and when running the game, the CPU usage is about 35% - and I can't accept that that's just how it has to be. This is how I'm going about rendering the map: I have the X and Y coordinates of the player, so I'm not drawing the whole map, just the visible portion of it; The number of visible tiles on screen varies according to the resolution chosen by the player (the CPU usage is 35% here when playing at a resolution of 1440x900); If the tile is "empty", I just skip drawing it (this didn't visibly lower the CPU usage, but reduced the drawing time in about 20ms); The map is composed of 5 layers - for more details; The tiles are 32x32 pixels; And just to be on the safe side, I'll post the code for drawing the game here, although it's as messy and unreadable as it can be T_T (I'll try to make it a little readable) private void drawGame(Graphics2D g2d){ //Width and Height of the visible portion of the map (not of the screen) int visionWidht = visibleCols * TILE_SIZE; int visionHeight = visibleRows * TILE_SIZE; //Since the map can be smaller than the screen, I center it just to be sure int xAdjust = (getWidth() - visionWidht) / 2; int yAdjust = (getHeight() - visionHeight) / 2; //This "deducedX" thing is to move the map a few pixels horizontally, since the player moves by pixels and not full tiles int playerDrawX = listOfCharacters.get(0).getX(); int deducedX = 0; if (listOfCharacters.get(0).currentCol() - visibleCols / 2 >= 0) { playerDrawX = visibleCols / 2 * TILE_SIZE; map_draw_col = listOfCharacters.get(0).currentCol() - visibleCols / 2; deducedX = listOfCharacters.get(0).getXCol(); } //"deducedY" is the same deal as "deducedX", but vertically int playerDrawY = listOfCharacters.get(0).getY(); int deducedY = 0; if (listOfCharacters.get(0).currentRow() - visibleRows / 2 >= 0) { playerDrawY = visibleRows / 2 * TILE_SIZE; map_draw_row = listOfCharacters.get(0).currentRow() - visibleRows / 2; deducedY = listOfCharacters.get(0).getYRow(); } int max_cols = visibleCols + map_draw_col; if (max_cols >= map.getCols()) { max_cols = map.getCols() - 1; deducedX = 0; map_draw_col = max_cols - visibleCols + 1; playerDrawX = listOfCharacters.get(0).getX() - map_draw_col * TILE_SIZE; } int max_rows = visibleRows + map_draw_row; if (max_rows >= map.getRows()) { max_rows = map.getRows() - 1; deducedY = 0; map_draw_row = max_rows - visibleRows + 1; playerDrawY = listOfCharacters.get(0).getY() - map_draw_row * TILE_SIZE; } //map_draw_row and map_draw_col representes the coordinate of the upper left tile on the screen //iterate through all the tiles on screen and draw them - this is what consumes most of the CPU for (int col = map_draw_col; col <= max_cols; col++) { for (int row = map_draw_row; row <= max_rows; row++) { Tile[] tiles = map.getTiles(col, row); for(int layer = 0; layer < tiles.length; layer++){ Tile currentTile = tiles[layer]; boolean shouldDraw = true; //I only draw the tile if it exists and is not empty (id=-1) if(currentTile != null && currentTile.getId() >= 0){ //The layers above 1 can be draw behing or infront of the player according to where it's standing if(layer > 1 && currentTile.getId() >= 0){ if(playerBehind(col, row, layer, listOfCharacters.get(0))){ behinds.get(0).add(new int[]{col, row}); //the tiles that are infront of the player wont be draw right now shouldDraw = false; } } if(shouldDraw){ g2d.drawImage( tiles[layer].getImage(), (col-map_draw_col)*TILE_SIZE - deducedX + xAdjust, (row-map_draw_row)*TILE_SIZE - deducedY + yAdjust, null); } } } } } } There's some more code in this method but nothing relevant to this question. Basically, the biggest problem is that I iterate over around 5000 tiles (in this specific resolution) 60 times each second. I thought about rendering the visible portion of the map once and storing it into a BufferedImage and when the player moved move the whole image the same amount but to the opposite side and then drawn the tiles that appeared on the screen, but if I do it like that, I wont be able to have animated tiles (at least I think). That being said, any suggestions?

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• Looking for a better Factory pattern (Java)

  - by Sam Goldberg

  After doing a rough sketch of a high level object model, I am doing iterative TDD, and letting the other objects emerge as a refactoring of the code (as it increases in complexity). (That whole approach may be a discussion/argument for another day.) In any case, I am at the point where I am looking to refactor code blocks currently in an if-else blocks into separate objects. This is because there is another another value combination which creates new set of logical sub-branches. To be more specific, this is a trading system feature, where buy orders have different behavior than sell orders. Responses to the orders have a numeric indicator field which describes some event that occurred (e.g. fill, cancel). The combination of this numeric indicator field plus whether it is a buy or sell, require different processing buy the code. Creating a family of objects to separate the code for the unique handling each of the combinations of the 2 fields seems like a good choice at this point. The way I would normally do this, is to create some Factory object which when called with the 2 relevant parameters (indicator, buysell), would return the correct subclass of the object. Some times I do this pattern with a map, which allows to look up a live instance (or constructor to use via reflection), and sometimes I just hard code the cases in the Factory class. So - for some reason this feels like not good design (e.g. one object which knows all the subclasses of an interface or parent object), and a bit clumsy. Is there a better pattern for solving this kind of problem? And if this factory method approach makes sense, can anyone suggest a nicer design?

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• How do I left-click a Java Application on a WeTab running Ubuntu 12.10? (workaround defect in Onboard)

  - by Kat Amsterdam

  I installed Ubuntu 12.10 on my weTab. Everything works perfectly (albeit slowly) and I can touch and use every application execpt ones written in Java. When I start any Java Application the touchscreen does not recognize the left click. I believe it's a problem in OnBoard (the onscreen keyboard) because when I touch the mouse icon on the OnBoard and then the Java Application the left click works. This is very cumbersome for every click to first hit OnBoard mouse icon and then button in the Java app I would like to click. It defeats the purpose of a touchscreen. The Java Application is definitly touchable as it's running on 10 other machines with Elo Touchscreen. How do I get Ubuntu to recognize the left click in a java application automatically when I touch the screen? Or a way to dignose this so I can make a clear bug report? This happens in all the desktop environments (Gnome/Unity, XFCE4 and LXDE) I tried with openjdk-6-* and openjdk-7-* Stats: WeTab 32GB 3G 2GB RAM Intel(R) Atom(TM) CPU N450 @ 1.66GHz - 64-bit Ubuntu 12.10 - 64 bit Unity Desktop environment Xubuntu Desktop environment Lubuntu Desktop environment The real touchscreen driver from EETI (eGalaxy) (also didn't work with the Ubuntu standard touchscreen driver)

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• Java 2D Tile Collision

  - by opiop65

  I have been working on a way to do collision detection forever, and just can't figure it out. Here's my simple 2D array: for (int x = 0; x < 16; x++) { for (int y = 0; y < 16; y++) { map[x][y] = AIR; if(map[x][y] == AIR) { air.draw(x * tilesize, y * tilesize); } } } for (int x = 0; x < 16; x++) { for (int y = 6; y < 16; y++) { map[x][y] = GRASS; if(map[x][y] == GRASS) { grass.draw(x * tilesize, y * tilesize); } } } for (int x = 0; x < 16; x++) { for (int y = 8; y < 16; y++) { map[x][y] = STONE; if(map[x][y] == STONE) { stone.draw(x * tilesize, y * tilesize); } } } I want to do it with rectangles, and using the intersect() method, but how would I go about adding rectangles to all the tiles? Edit: My player moves like this: if(input.isKeyDown(Input.KEY_W)) { shiftY -= delta * speed; idY = (int) shiftY; if(shift == true) { shiftY -= delta * runspeed; } if(isColliding == true) { shiftY += delta * speed; } } if(input.isKeyDown(Input.KEY_S)) { shiftY += delta * speed; idY = (int) shiftY; if(shift == true) { shiftY += delta * runspeed; } if(isColliding == true) { shiftY -= delta * speed; } } if (input.isKeyDown(Input.KEY_A)) { steve = left; shiftX -= delta * speed; idX = (int) shiftX; if(shift == true) { shiftX -= delta * runspeed; } if(isColliding == true) { shiftX += delta * speed; } } if (input.isKeyDown(Input.KEY_D)) { steve = right; shiftX += delta * speed; idX = (int) shiftX; if(shift == true) { shiftX += delta * runspeed; } if(isColliding == true) { shiftX -= delta * speed; } } (I have tried my own collision code, but its horrible. Doesn't work in the slightest)

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• UnsatisfiedLinkError: no swt-gtk-4233

  - by Abogical

  I'm a Java newbie who just a made a simple Java program using SWT for GUI via eclipse Juno. The code was working and the program was able to run inside eclipse, so I compiled it and made it a runnable jar file so it can be run outside eclipse. I tried to run it using the terminal and this error came up. Exception in thread "main" java.lang.UnsatisfiedLinkError: Could not load SWT library. Reasons: no swt-gtk-4233 in java.library.path no swt-gtk in java.library.path Can't load library: /home/abody/.swt/lib/linux/x86_64/libswt-gtk-4233.so Can't load library: /home/abody/.swt/lib/linux/x86_64/libswt-gtk.so at org.eclipse.swt.internal.Library.loadLibrary(Library.java:331) at org.eclipse.swt.internal.Library.loadLibrary(Library.java:240) at org.eclipse.swt.internal.C.<clinit>(C.java:21) at org.eclipse.swt.internal.Converter.wcsToMbcs(Converter.java:63) at org.eclipse.swt.internal.Converter.wcsToMbcs(Converter.java:54) at org.eclipse.swt.widgets.Display.<clinit>(Display.java:133) at Class1.main(Class1.java:12) So now it looks like it can't find "libswt-gtk-4233.so" and the other file. However, when I took a look at he ".swt" folder I had an "libswt-gtk-3740.so" not 4233. So its trying to find a file that is more up-to-date. So what does that mean, should I update SWT? what's going on?

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• Using a Higher Precision (than 8-bit unsigned integer) Buffered Image for Heightmaps in Java

  - by pl12

  I am generating a heightmap for every quad in my quadtree in openCL. The way I was creating the image is as follows: DataBufferInt dataBuffer = (DataBufferInt)img.getRaster().getDataBuffer(); int data[] = dataBuffer.getData(); //img is a bufferedimage inputImageMem = CL.clCreateImage2D( context, CL_MEM_READ_WRITE | CL_MEM_USE_HOST_PTR, new cl_image_format[]{imageFormat}, size, size, size * Sizeof.cl_uint, Pointer.to(data), null); This works ok but the major issue is that as the quads get smaller and smaller the 8-bit format of the buffered image starts to cause intolerable "stepping" issues as seen below: I was wondering if there was an alternate way I could go about doing this? Thanks for the time.

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• Java chunk negative number problem

  - by user1990950

  I've got a tile based map, which is divided in chunks. I got a method, which puts tiles in this map and with positive numbers it's working. But when using negative numbers it wont work. This is my setTile method: public static void setTile(int x, int y, Tile tile) { int chunkX = x / Chunk.CHUNK_SIZE, chunkY = y / Chunk.CHUNK_SIZE; IntPair intPair = new IntPair(chunkX, chunkY); world.put(intPair, new Chunk(chunkX, chunkY)); world.get(intPair).setTile(x - chunkX * Chunk.CHUNK_SIZE, y - chunkY * Chunk.CHUNK_SIZE, tile); } This is the setTile method in the chunk class (CHUNK_SIZE is a constant with the value 64): public void setTile(int x, int y, Tile t) { if (x >= 0 && x < CHUNK_SIZE && y >= 0 && y < CHUNK_SIZE) tiles[x][y] = t; } What's wrong with my code?

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• Java 2D World question

  - by Munkybunky

  I have a 2D world background made up of a Grid of graphics, which I display on screen with a viewport (800x600) and it all works. My question is I have the following code to convert the mouse co-ordinates to world co-ordinates then World co-ordinates to grid co-ordinates then grid co-ordinates to screen co-ordinates. //Add camerax to mouse screen co-ords to convert to world co-ords. int cursorx_world=(int)camerax+(int)GameInput.mousex; int cursorx_grid=(int)cursorx_world/blocksize; // World Co-ords / gridsize give grid co-ords int cursorx_screen=-(int)camerax+(cursorx_grid*blocksize); So is there anyway I can convert straight from mouse screen co-ords to screen co-ordinates?

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• Java best practice Interface - subclasses and constants

  - by Taiko

  In the case where a couple of classes implements an interface, and those classes have a couple of constants in common (but no functions), were should I put this constant ? I've had this problem a couple of times. I have this interface : DataFromSensors that I use to hide the implementations of several sub classes like DataFromHeartRateMonitor DataFromGps etc... For some reason, those classes uses the same constants. And there's nowere else in the code were it is used. My question is, were should I put those constants ? Not in the interface, because it has nothing to do with my API Not in a static Constants class, because I'm trying to avoid those Not in a common abstract class, that would stand between the interface and the subclasses, because I have no functions in common, only a couple of constants (TIMEOUT_DURATION, UUID, those kind of things) I've read best practice for constants and interface to define constants but they don't really answer my question. Thanks !

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• Why avoid Java Inheritance "Extends"

  - by newbie

  Good day! Jame Gosling said “You should avoid implementation inheritance whenever possible.” and instead, use interface inheritance. But why? How can we avoid inheriting the structure of an object using the keyword "extends", and at the same time make our code Object Oriented? Could someone please give an Object Oriented example illustrating this concept in a scenario like "ordering a book in a bookstore?" Thank you in advance.

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• Java getResourceAsStream as local resource

  - by Dajgoro Labinac

  Before using LWJGL, I used the Graphic method, and there I displayed imageicons, and I had the picture file located in the resources. I used: ImageIcon tcard = new ImageIcon(this.getClass().getResource("RCA.png")); to load the image. Now when I load textures in LWJGL, I have to use absolute paths to locate the file: tcard = TextureLoader.getTexture("PNG", ResourceLoader.getResourceAsStream("C:/RCA.png")); I tried Googling, but I didn't find anything helpful. How can I load the image from the local resources like in the first example?

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• java 2d game how to make a player jump

  - by user2957632

  Hi I'm making a 2d plat former running game kind of like jetpack joyride fro example were u are constantly running but there is obstacles and u need to jump over them. but I want the character to jump and come back down. here is some of my code. if (listen.ml == true) { if (y > 120) { jump = true; y -= 1; } } if (y == 121 && jump == true) { jump = false; y += 1; }

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• Reasons behind polymorphism related behaviour in java

  - by Shades88

  I read this code somewhere class Foo { public int a; public Foo() { a = 3; } public void addFive() { a += 5; } public int getA() { System.out.println("we are here in base class!"); return a; } } public class Polymorphism extends Foo{ public int a; public Poylmorphism() { a = 5; } public void addFive() { System.out.println("we are here !" + a); a += 5; } public int getA() { System.out.println("we are here in sub class!"); return a; } public static void main(String [] main) { Foo f = new Polymorphism(); f.addFive(); System.out.println(f.getA()); // SOP 1 System.out.println(f.a); // SOP 2 } } For SOP1 we get answer 10 and for SOP2 we get answer 3. Reason for this is that you can't override variables whereas you can do so for methods. This happens because type of the reference variable is checked when a variable is accessed and type of the object is checked when a method is accessed. But I am wondering, just why is it that way? Can anyone explain me what is the reason for this behaviour

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