nullpointerexception

问题 I'm using JSF Composite Component for reuse component. However, I keep getting a null-pointer error, I follow some of the tutorial I found but none mention this problem. The stack trace added: java.lang.NullPointerException at com.sun.faces.application.view.FaceletViewHandlingStrategy$MethodRetargetHandlerManager$ArbitraryMethodRegargetHandler.retarget(FaceletViewHandlingStrategy.java:1883) at com.sun.faces.application.view.FaceletViewHandlingStrategy.retargetMethodExpressions

问题 I´m currentl trying to get into JavaFX 2.0 but I can´t get .css Stylesheets to work within my application. I´ve followed the guide at http://docs.oracle.com/javafx/2/get_started/css.htm#BABBGJBI but whenever I try to import a .css file via scene.getStylesheets().add(Login.class.getResource("loginform.css").toExternalForm()); I get the following Error: Exception in Application start method Exception in thread "main" java.lang.RuntimeException: Exception in Application start method at com.sun

问题 I'm trying to build an android RSS reader app but I keep getting a Null pointer exception. I'm new to java and can't tell if its the feed url not returning any data or the data not being stored properly. my logcat reads: 08-08 18:44:25.840: E/Trace(621): error opening trace file: No such file or directory (2) 08-08 18:44:25.910: W/ActivityThread(621): Application com.app.fullmetalmanga is waiting for the debugger on port 8100... 08-08 18:44:25.930: I/System.out(621): Sending WAIT chunk 08-08

问题 when i build a jar file and run it ,it shows a null pointer exception due to imageicon not found new ImageIcon(getClass().getClassLoader().getResource("icons/exit.png"))); this is the error what i get when i run the jar file Exception in thread "main" java.lang.NullPointerException at javax.swing.ImageIcon.<init>(Unknown Source) at mediaplayer.MediaPlayer.buildtoolbar(MediaPlayer.java:130) at mediaplayer.MediaPlayer.<init>(MediaPlayer.java:81) at mediaplayer.MediaPlayer.main(MediaPlayer.java

问题 This question's answers are a community effort . Edit existing answers to improve this post. It is not currently accepting new answers or interactions. What are Null Pointer Exceptions ( java.lang.NullPointerException ) and what causes them? What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely? 回答1: When you declare a reference variable (i.e. an object) you are really creating a pointer to an object. Consider

问题 It seems to be a common problem, but after hours of trying random solutions provided as answers to similar questions, my code still produces a NullPointerException when I access a Fragment's textView from an Activity. I can include (and view) my Fragment when its textView has a predefined Text or by using setText() in onCreateView() of the Fragment class but not by using a setter method (here set_message_success() ). This is my Fragment class Fragment_Message : public class Fragment_Message

问题 I am trying sort the ArrayList with 3 Card in it. I am doing this with a Comparator. (Is this overkill)? Card.getRank() returns an integer between 2 and 14. I have absolutely no idea where I am going wrong. I have done this successfully before, and compared with my other code, and it seems the same. I would greatly appreciate if someone could spread some light on this! public int getHand(Card c1, Card c2, Card c3) { ArrayList<Card> hand = new ArrayList<Card>(); hand.add(c1); hand.add(c2);

问题 This is probably a simple one to answer but I can't seem to get right and thought I would ask. I am getting a java.lang.IllegalArgumentException and a java.lang.NullPointerException Here is the error log 03-20 13:13:22.872: E/SurfaceTextureClient(565): dequeueBuffer failed (No such device) 03-20 13:13:22.879: E/BaseSurfaceHolder(565): Exception locking surface 03-20 13:13:22.879: E/BaseSurfaceHolder(565): java.lang.IllegalArgumentException 03-20 13:13:22.879: E/BaseSurfaceHolder(565): at

问题 I have a bean like this: @Component @DependsOn("SomeType") Class A{ @Autowired SomeType one; String two = one.someMethod(); int three; } In my application context xml, I have: <bean id="two" class="a.b.c.SomeType"></bean> <context:component-scan base-package="a.b.c"/> <context:annotation-config/> But while Spring instantiates the bean, it throws a NullPointerException . So I'm wondering if the field two is initialized before field one , causing the NPE. Can anyone tell me in which order

问题 I've been trying to convert from mybatis2 to mybatis3 and its giving me all sorts of problems. From the stacktrace im getting a Error Parsing Mapper XML for sqlMapConfig.xml which I take it means there is something wrong there however I cannot see it. I would greatly appreciate any help. sqlMapConfig.xml <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <settings> <setting name="cacheModelsEnabled" value="true" /