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PONullPointerException when calling a getter
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copied!<p>I have already done research on this question, and also tried to figure it out by myself but no luck. So I decided to ask it.</p> <p><b>Basic info:</b></p> <p>There are two classes. <code>FBClient</code>, and <code>State</code>. In <code>FBClient</code>, I have a static variable of it's type, <code>fbc</code>, a <code>StateManager</code> instance, which just has some methods to work with <code>State</code> stuff, some constants and two getters. In <code>State</code>, I am trying to initialize a <code>BufferedImage</code>.</p> <pre><code>public class FBClient { //Static public static FBClient fbc; //In init method private StateManager stateManager; //Constants private final int INIT_FRAME_WIDTH = 320, INIT_FRAME_HEIGHT = (INIT_FRAME_WIDTH / 4) * 3, SCALE = 3, FRAME_WIDTH = INIT_FRAME_WIDTH * SCALE, FRAME_HEIGHT = INIT_FRAME_HEIGHT * SCALE; public static void main(String[] args) { try { //First call in exception chain: fbc = new FBClient(); } catch (Exception e) { e.printStackTrace(); System.exit(1); } } private FBClient() throws IOException { //Second call in exception chain: init(); } private void init() throws IOException { stateManager = new StateManager(); //Third call in exception chain: stateManager.addState(new MainMenu((byte) 0, "Main Menu")); //MainMenu is the subclass of State, and the constructor just calls "super(0, "Main Menu")" } public int getFRAME_HEIGHT() { return FRAME_HEIGHT; } public int getFRAME_WIDTH() { return FRAME_WIDTH; } } public abstract class State { protected final byte ID; protected final String NAME; protected final BufferedImage SCREEN; protected final Graphics2D GRAPHICS; public State(byte id, String name) { this.ID = id; this.NAME = name; //Exception cause: this.SCREEN = new BufferedImage(FBClient.fbc.getFRAME_WIDTH(), FBClient.fbc.getFRAME_HEIGHT(), BufferedImage.TYPE_INT_RGB); this.GRAPHICS = SCREEN.createGraphics(); } } </code></pre> <p><b>More info:</b></p> <p>If I put literals in BufferedImage initialization it works.</p> <p>If I initialize two variables in the <code>State</code> class, assigning them literals and putting those variables in initialization, it works.</p> <p>If instead of assigning literals to those variables I assign them <code>FBClient.fbc.getFRAME_WIDTH()</code> and <code>FBClient.fbc.getFRAME_HEIGHT()</code>, it throws a <code>NullPointerException</code>.</p> <p>If I make a <code>System.out.println(getFRAME_WIDTH + " : " + getFRAME_HEIGHT)</code> in <code>FBClient</code> class, it prints out properly, but if I do it in <code>State</code> class (and off course adding <code>FBClient.fbc.</code> before it), it throws a <code>NullPointerException</code>.</p> <p>If I make <code>FRAME_WIDTH</code> and <code>FRAME_HEIGHT</code> constants <code>public</code>, and I try to access them from <code>State</code> class by doing <code>FBClient.fbc.FRAME_WIDTH</code> and <code>FRAME_HEIGHT</code>, it throws a <code>NullPointerException</code>.</p> <p>If I try to access the constants from <code>FBClient</code> class directly, instead of getters, it still prints out properly.</p> <p><b>Finally</b></p> <p>Thank you for taking your time, and if you need more information to work with, ask me in the comments and I'll provide it. Also, I apologise if the question is not constructed well/not explained well. If that's the case, tell me how can I improve it. And also, I apologise if this question was asked and answered once already, I may have missed it, but as I said, I did my research.</p> <p><b>Edit #1</b></p> <p>A comment suggested I print out a <code>fbc</code> value, to see if it's null. So I added this line of code to the <code>State</code> constructor: <code>if(FBClient.fbc != null) System.out.println("Not null"); else System.out.println("Null");</code> And, as suspected, it printed out null. Why is that? I clearly initialized the variable in the <code>main</code> method...</p>

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