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POGetting NullPointerException while creating a game
 

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  1. POGetting NullPointerException while creating a game
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    <p>I'm creating a game. It doesn't throw an error in Eclipse, but when I run it in debug mode it throws a <code>NullPointerException</code> at line: </p> <pre><code>System.out.println("Stone x: " + blocks.get(BlockRectangle.getByID(rectID)).getX() + " y: " + blocks.get(BlockRectangle.getByID(rectID)).getY()); </code></pre> <p>Game.java:</p> <pre><code>package lt.projecturanium; import java.awt.BorderLayout; import java.awt.Canvas; import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.image.BufferStrategy; import java.util.HashMap; import javax.swing.JFrame; import lt.projecturanium.blocks.Block; import lt.projecturanium.blocks.BlockRectangle; import lt.projecturanium.entity.Player; @SuppressWarnings("unused") public class Game extends Canvas implements Runnable{ private static final long serialVersionUID = 1L; private static JFrame _frame; public static Game _instance; private static final String TITLE = "Project Uranium"; private static final int WIDTH = 650; private static final int HEIGHT = WIDTH * 3 / 4; private static final int UPDATE_RATE = 50; private static final int RENDER_RATE = 100; public static HashMap&lt;Block, Coordinates&gt; blocks = new HashMap&lt;Block, Coordinates&gt;(); public int rectx = 0; public int recty = 0; public int rectID = 0; public boolean hitted = false; public float interpolation; public static final Dimension SIZE = new Dimension(WIDTH, HEIGHT); private Thread _thread; private boolean _running; private int _totalTicks = 0; private int _tps = 0; private int _fps = 0; public Game() { _instance = this; setPreferredSize(SIZE); setMinimumSize(SIZE); setMaximumSize(SIZE); _frame = new JFrame(TITLE); _frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); _frame.setLayout(new BorderLayout()); _frame.add(_instance, BorderLayout.CENTER); _frame.pack(); _frame.setResizable(false); _frame.setLocationRelativeTo(null); _frame.setVisible(true); createBufferStrategy(2); blocks.put(new Block(new BlockRectangle(200)), new Coordinates(30, 50)); } public synchronized void start() { _running = true; _thread = new Thread(this, TITLE+"_main"); _thread.start(); } public synchronized void stop() { _running = false; if (_thread != null) { try { _thread.join(); } catch (InterruptedException e) { e.printStackTrace(); } } } public void paint(Graphics g) { super.paint(g); // fixes the immediate problem. Graphics2D g2 = (Graphics2D) g; g2.drawString("FPS: " + _fps + "\n TPS: " + _tps, 10, 10); if (hitted) { recty = 0; rectx += 21; rectID++; blocks.put(new Block(new BlockRectangle(rectID)), new Coordinates(rectx, recty)); hitted = false; } recty++; g2.drawImage(Player.getTexture(), 60, 60, null); g2.drawRect(rectx, recty, 20, 20); g2.setColor(new Color(101, 67, 33)); g2.fillRect(0, 430, getWidth(), getHeight()); g2.setColor(new Color(0, 100, 0)); g2.fillRect(0, 420, getWidth(), 10); g2.setColor(Color.BLACK); if (recty == (419 - 20)) { hitted = true; } } public void run() { double lastUpdateTime = System.nanoTime(); double lastRenderTime = lastUpdateTime; final int ns = 1000000000; final double nsPerUpdate = (double) ns / UPDATE_RATE; final double nsPerRender = (double) ns / RENDER_RATE; final int maxUpdatesBeforeRender = 5; int lastSecond = (int) (lastUpdateTime / ns); int tickCount = 0; int renderCount = 0; while (_running) { long currTime = System.nanoTime(); int tps = 0; while ((currTime - lastUpdateTime) &gt; nsPerUpdate &amp;&amp; tps &lt; maxUpdatesBeforeRender) { update(); tickCount++; _totalTicks++; tps++; lastUpdateTime += nsPerUpdate; interpolation = Math.min(1.0F, (float) ((currTime - lastUpdateTime) / nsPerUpdate)); render(interpolation, getGraphics()); } if (currTime - lastUpdateTime &gt; nsPerUpdate) { lastUpdateTime = currTime - nsPerUpdate; } if (currTime - lastRenderTime == maxUpdatesBeforeRender + 1) { render(interpolation, getGraphics()); } renderCount++; lastRenderTime = currTime; int currSecond = (int) (lastUpdateTime / ns); if (currSecond &gt; lastSecond) { _tps = tickCount; _fps = renderCount; tickCount = 0; renderCount = 0; lastSecond = currSecond; _frame.setTitle(TITLE + " | TPS: " + _tps + " | FPS: "+ _fps); } while (currTime - lastRenderTime &lt; nsPerRender &amp;&amp; currTime - lastUpdateTime &lt; nsPerUpdate) { Thread.yield(); try { Thread.sleep(1); } catch (InterruptedException e) { e.printStackTrace(); } currTime = System.nanoTime(); } } } public void update() { _frame.pack(); } public void render(float interp, Graphics g) { BufferStrategy myStrategy = getBufferStrategy(); Graphics gra = myStrategy.getDrawGraphics(); paint(gra); g.dispose(); myStrategy.show(); //System.out.println("Grass x: " + blocks.get("grass").getX() + " y: " + blocks.get("grass").getY()); System.out.println("Stone x: " + blocks.get(BlockRectangle.getByID(rectID)).getX() + " y: " + blocks.get(BlockRectangle.getByID(rectID)).getY()); } } </code></pre> <p>BlockRectangle.java:</p> <pre><code>package lt.projecturanium.blocks; import java.awt.Image; import java.io.IOException; import java.util.HashMap; import javax.imageio.ImageIO; import lt.projecturanium.Game; public class BlockRectangle extends Block{ private int id; private static HashMap&lt;Integer, BlockRectangle&gt; rects = new HashMap&lt;Integer, BlockRectangle&gt;(); public BlockRectangle(int id) { super(); this.id = id; rects.put(id, this); } public int getID() { return this.id; } public static BlockRectangle getByID(int id) { return rects.get(id); } public static Image getTexture() { try{ return ImageIO.read(Game._instance.getClass().getClassLoader().getResource("../res/player.png")); } catch(IOException e) { e.printStackTrace(); } return null; } } </code></pre> <p>Block.java:</p> <p>package lt.projecturanium.blocks;</p> <pre><code>public class Block { private Block block; public Block (Block block){ this.block = block; } public Block getBlock() { return block; } public Block getBlockById(int id) { return block; } public Block() { } } </code></pre> <p>Error:</p> <pre><code>Thread [Project Uranium_main] (Suspended (exception NullPointerException)) Game.render(float, Graphics) line: 186 Game.run() line: 139 Thread.run() line: not available </code></pre>
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    1. COCan you add the error output to the question?
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    2. CO`I think you know that i'm creating a game.` -- Didn't know thus far, but will keep a note of it.
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    3. COWhat do you mean by "it doesn't throw an error in Eclipse"? Do you mean that Eclipse doesn't report a compilation error? You are debugging it within Eclipse, right?
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      1. POGetting NullPointerException while creating a game
      1. USMarko Topolnik
 

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