nullpointerexception

问题 Once I click on a anchor tag on my jsp page, it perfectly works but the following exception will be thrown in console, based on this answer, I removed the jap-api*.jar files from my dependencies folder but the application still throws the exception. WARNING: Servlet.service() for servlet jsp threw exception java.lang.NullPointerException at org.apache.jsp.products.ProductShow_jsp._jspx_meth_c_if_1(ProductShow_jsp.java:211) at org.apache.jsp.products.ProductShow_jsp._jspService(ProductShow_jsp

问题 Hi i'm new bee to android. while executing my application I'm getting nullpoint exception error, dont know why it is happening. please any one help me to get rid from this issue. thanks in advance. This is my logcat: 09-14 12:30:14.027: INFO/System.out(365): Constructor StudentList Adapter... 09-14 12:30:14.027: DEBUG/AndroidRuntime(365): Shutting down VM 09-14 12:30:14.027: WARN/dalvikvm(365): threadid=1: thread exiting with uncaught exception (group=0x4001d800) 09-14 12:30:14.047: ERROR

问题 when you click to go from one activity to another, I have an error: java.lang.RuntimeException: Unable to start activity ComponentInfo {...}: java.lang.NullPointerException I am missing some method? Please help me to understand what I did wrong, which is why you see this error? My activity: Zaselenie.java import java.util.ArrayList; import android.app.Activity; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle; import android.util.Log;

问题 I am following the tutorial of https://androidbelieve.com/navigation-drawer-with-swipe-tabs-using-design-support-library/ to implement sliding tablayout. It works perfect for empty fragments, However, I have 3 fragments with LoaderManagers and recyclerViews, each one loads different data. When the app loaded at the first time, if I click from the first fragment to the third fragment on the tabLayout without sliding or clicking to second one, it crashes. The data was not loading, as it

问题 If you run the following code, public class Foo{ public static void main(String[] args){ int id = new Bar().getId(); // throws unexpected NullPointerException } private static class Bar{ private final Integer id; public Bar(){ this(null); } public Bar(Integer id){ this.id = id; } public Integer getId(){ return id; } } } you will get the following stacktrace, Exception in thread "main" java.lang.NullPointerException at Foo.main(Foo.java:3) How come there's no compiler warning or anything? IMHO

问题 I've been struggling with this issue for a little while now. Found several posts about it but none solved my problem. It will probably have something to do with the fact that a SecurityContext is boud to a specific Thread but even then I do not know how to solve it: Consider following code to retrieve the user that was logged in: SecurityContextHolder.getContext().getAuthentication().getPrincipal() Running this code in a controller would return (correctly) the user logged in. Running this

问题 Please I have this question which is a bit theoretical, but I would like to understand it. Why if I pass a null argument to a constructor do I get a NullPointerException ? This is my example new AttendeeDetail("Gus Goose","1151","15-01-2012",(Integer) null,null) This is the class: public class AttendeeDetail { private String ticketholder_name; private String user_id; private String date_of_birth; private int tickets_purchased; private ArrayList<Ticket> tickets; public AttendeeDetail(String

问题 So there is bug that keeps coming up with out anything in the trace related to me, here is a sample trace: java.lang.NullPointerException at android.app.ActivityThread.handleStopActivity(ActivityThread.java:2484) at android.app.ActivityThread.access$1800(ActivityThread.java:117) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:948) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:130) at android.app.ActivityThread.main

问题 So there is bug that keeps coming up with out anything in the trace related to me, here is a sample trace: java.lang.NullPointerException at android.app.ActivityThread.handleStopActivity(ActivityThread.java:2484) at android.app.ActivityThread.access$1800(ActivityThread.java:117) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:948) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:130) at android.app.ActivityThread.main

问题 I am new to Java. I just read that class variables in Java have default value. I tried the following program and was expecting to get the output as 0 , which is the default value on an integer, but I get the NullPointerException . What am I missing? class Test{ static Integer iVar; public static void main(String...args) { System.out.println(iVar.intValue()); } } 回答1: You are right, uninitialized class variables in Java have default value assigned to them. Integer type in Java are not same as