I am working an a small database assignment, and I seem to get a weird nullPointerException where I cannot find the problem
The following snippet is the error:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at interfaces.FindDueActivityForFriend$1.actionPerformed(FindDueActivityForFriend.java:65)
at java.awt.Button.processActionEvent(Unknown Source)
at java.awt.Button.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
As you can see the problem occurs in the 65 of the FindDueActivityForFriend class, and to be more specific in this code snippet:
friendSearch = friendSearchField.getText();
console.out("Searching for the name that was entered");
console.out("friendSearch variable is: " + friendSearch );
if(con.GetNameExcists(friendSearch )){
//more code
the error occurs at the if statement.
In this if statement a class is called that connects to the database, checks if a name is already in the database, and then returns a true if that name is already in the database.
I have used that specific method around 10 times around the program without problems, but not this time.
the console.out("String"); that I am calling just before it is for a small console windows that I made that just prints what I tell it to, this is to have a console when not running the application out of for example eclipse.
I tried printing the variable just to see what it was, and it is not null.
following is a copy paste of the console:
[Wed May 14 20:04:26 CEST 2014] [INFO] Opened the findDueForFriend screen
[Wed May 14 20:04:30 CEST 2014] [INFO] Searching for the name that was entered
[Wed May 14 20:04:30 CEST 2014] [INFO] FriendSearch variable is: Ylva
I went on into ant debugger, and is doesn't even go in the method, it throws the nullpointer before actually opening the method
I don't have a clue what I am doing wrong anymore so if anyone has any suggestions please post them.
just for completeness here is the declaration of the variable aswell:
String friendSearch;
public FindDueActivityForFriend(Console Console){
console = Console;
friendSearch = "";
I even tried declaring the String as an empty string, not sure if that makes it not null but I think it should, and the console window clearly shows that the string contains something before throwing the nullpointer exception...
If it occurs in this if statement
if(con.GetNameExcists(friendSearch ))
and you know that friendSearch is not null, then con must be null, in order to get a NullPointerException in the if statement.
the only possibility with the below code is
if(con.GetNameExcists(friendSearch ))
either con is null or friendSearch is null which you might be accessing at the
begining of the method and performing some operation like friendSearch.caoncat or something.
mostly it should be con is null it seems.
try to print con value inside log.
if con.getNameExcists(...) return Boolean instead of boolean and possibly returns null, then you get a NullPointerException from auto-unboxing.
Related
A couple days ago, I got a support ticket for this NullPointerException:
com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract com.redacted.SalesResponsePagination com.redacted.StatisticsService.findSalesData(com.redacted.ConfStats) throws com.redacted.AsyncException' threw an unexpected exception: java.lang.NullPointerException
at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:389)
at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:579)
at ... (typical GWT + Tomcat stacktrace)
Caused by: java.lang.NullPointerException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at java.util.concurrent.ForkJoinTask.getThrowableException(Unknown Source)
at java.util.concurrent.ForkJoinTask.reportException(Unknown Source)
at java.util.concurrent.ForkJoinTask.invoke(Unknown Source)
at java.util.stream.ForEachOps$ForEachOp.evaluateParallel(Unknown Source)
at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateParallel(Unknown Source)
at java.util.stream.AbstractPipeline.evaluate(Unknown Source)
at java.util.stream.ReferencePipeline.forEach(Unknown Source)
at com.redacted.StatisticsControllerImpl.replacePrices(StatisticsControllerImpl.java:310)
at com.redacted.StatisticsControllerImpl.findSalesData(StatisticsControllerImpl.java:288)
at com.redacted.StatisticsServiceImpl.findSalesData(StatisticsServiceImpl.java:83)
at sun.reflect.GeneratedMethodAccessor752.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:561)
... 33 more
Caused by: java.lang.NullPointerException
at com.redacted.StatisticsControllerImpl.lambda$replacePrices$27(StatisticsControllerImpl.java:317)
at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(Unknown Source)
at ... (typical stream.forEach stacktrace)
Now, this was an easy one because the exact line number for the NPE was in plain sight; all I had to do was go to StatisticsControllerImpl.java:317:
salesResponsePagination.getSalesResponses().parallelStream()
.peek(sr -> /*...*/)
.filter(sr -> /*...*/)
/*310*/ .forEach(sr -> {
final List<CartElement> sentCEs = DaoService.getCartElementDAO().getSentCEs(/*...*/);
if (sentCEs != null && !sentCEs.isEmpty() && sentCEs.get(0) != null) {
final CartElement ce = sentCEs.get(0);
// some more non-NPE lines...
/*317*/ if (sr.getCurrency().equals(ce.getPurchaseCurrency()) && sr.getPrice().equals(ce.getPurchasePrice().intValue()) && !ce.getCurrency().equals(ce.getPurchaseCurrency())) {
// Some currency exchanging
}
// Etcetera (about 12 lines more)
});
And replace the .equals() calls with Object.equals() to avoid the NPE (investigating the reasons why some sales were registered with a NULL price or currency came later). Test, commit, push, send ticket to QA.
However, the next day QA returned the ticket saying that the NPE persisted, and they included a new, almost similar stack trace:
com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract com.redacted.SalesResponsePagination com.redacted.StatisticsService.findSalesData(com.redacted.ConfStats) throws com.redacted.AsyncException' threw an unexpected exception: java.lang.NullPointerException
at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:389)
at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:579)
at ... (typical GWT + Tomcat stacktrace)
Caused by: java.lang.NullPointerException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at java.util.concurrent.ForkJoinTask.getThrowableException(Unknown Source)
at java.util.concurrent.ForkJoinTask.reportException(Unknown Source)
at java.util.concurrent.ForkJoinTask.invoke(Unknown Source)
at java.util.stream.ForEachOps$ForEachOp.evaluateParallel(Unknown Source)
at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateParallel(Unknown Source)
at java.util.stream.AbstractPipeline.evaluate(Unknown Source)
at java.util.stream.ReferencePipeline.forEach(Unknown Source)
at com.redacted.StatisticsControllerImpl.replacePrices(StatisticsControllerImpl.java:310)
at com.redacted.StatisticsControllerImpl.findSalesData(StatisticsControllerImpl.java:288)
at com.redacted.StatisticsServiceImpl.findSalesData(StatisticsServiceImpl.java:83)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:561)
... 33 more
Caused by: java.lang.NullPointerException
This stack trace was exactly the same as the previous one, except for two things:
This call was using NativeMethodAccessorImpl instead of GeneratedMethodAccessor752. Compare:
at com.redacted.StatisticsServiceImpl.findSalesData(StatisticsServiceImpl.java:83)
at sun.reflect.GeneratedMethodAccessor752.invoke(Unknown Source)
vs
at com.redacted.StatisticsServiceImpl.findSalesData(StatisticsServiceImpl.java:83)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
This one was missing the stack trace for the lambda. The line where the NPE happened was missing.
This threw me off initially. Why was the last part of the stack trace missing? I asked QA to re-test and re-attach the stack trace a couple times, until I got a complete one; however, the complete one I got in the end was based on GeneratedMethodAccesor once again.
Now, if I understand correctly, sun.reflect.NativeMethodAccessorImpl is used for the first invocations of a method, until JIT has enough info to generate an optimized accesor for that method in the form of sun.reflect.GeneratedMethodAccessorNNN.
What I don't understand is: if Native is using my code and Generated is using JIT's generated code, shouldn't Native show more info about my code, not less?
So my question is:
Why do lambda runtime exceptions thrown inside sun.reflect.NativeMethodAccessorImpl seem to be missing the lambda's stack trace?
Can this be a bug in JDK's source code? Especially when the very same exception thrown inside sun.reflect.GeneratedMethodAccessor includes the lambda stack trace without problem.
The following code manages to get a stack trace similar to the first one. I can force the use of NativeMethodAccessor or GeneratedMethodAccesor by running it with a sufficiently low or high first parameter, respectively (i.e. java test.Main 1 or java test.Main 30).
However, the lambda part of it is always present, whether using Native or Generated.
package test;
import java.lang.reflect.Method;
import java.util.stream.IntStream;
class MyOtherClass {
public void methodWithLambda(boolean fail) {
IntStream.range(0, 1000).parallel().forEach(k -> {
if (fail && k % 500 == 0)
throw new NullPointerException();
});
}
public String methodProxy(boolean fail) {
methodWithLambda(fail);
return "OK";
}
}
class MyClass {
public String methodReflected(Boolean fail) {
return new MyOtherClass().methodProxy(fail);
}
}
class Main {
public static void main(String[] args) throws Exception {
Class<MyClass> clazz = MyClass.class;
Object instance = clazz.newInstance();
Method method = clazz.getMethod("methodReflected", Boolean.class);
int reps = args.length >= 1 ? Integer.valueOf(args[0]) : 20;
for (; reps --> 0;) {
// Several non-failing calls to force creation of GeneratedMethodAccesor
System.out.println((String) method.invoke(instance, false));
}
// Failing call
System.out.println((String) method.invoke(instance, true));
}
}
Stack trace for the above code when using NativeMethodAccesor:
Exception in thread "main" java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at test.Main.main(Main.java:36)
Caused by: java.lang.NullPointerException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at java.util.concurrent.ForkJoinTask.getThrowableException(Unknown Source)
at java.util.concurrent.ForkJoinTask.reportException(Unknown Source)
at java.util.concurrent.ForkJoinTask.invoke(Unknown Source)
at java.util.stream.ForEachOps$ForEachOp.evaluateParallel(Unknown Source)
at java.util.stream.ForEachOps$ForEachOp$OfInt.evaluateParallel(Unknown Source)
at java.util.stream.AbstractPipeline.evaluate(Unknown Source)
at java.util.stream.IntPipeline.forEach(Unknown Source)
at java.util.stream.IntPipeline$Head.forEach(Unknown Source)
at test.MyOtherClass.methodWithLambda(Main.java:8)
at test.MyOtherClass.methodProxy(Main.java:14)
at test.MyClass.methodReflected(Main.java:21)
... 5 more
Caused by: java.lang.NullPointerException
at test.MyOtherClass.lambda$methodWithLambda$0(Main.java:10)
at java.util.stream.ForEachOps$ForEachOp$OfInt.accept(Unknown Source)
at java.util.stream.Streams$RangeIntSpliterator.forEachRemaining(Unknown Source)
at java.util.Spliterator$OfInt.forEachRemaining(Unknown Source)
at java.util.stream.AbstractPipeline.copyInto(Unknown Source)
at java.util.stream.ForEachOps$ForEachTask.compute(Unknown Source)
at java.util.concurrent.CountedCompleter.exec(Unknown Source)
at java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
at java.util.concurrent.ForkJoinPool$WorkQueue.execLocalTasks(Unknown Source)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(Unknown Source)
at java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
at java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)
EDIT: Just to be clear: I am not looking for ways to fix this NPE, nor ways to force the lambda's stack trace to print. What I want to know is the reason why the above happens: different implementations? A bug? Something to do with forEach()?
This might be an issue of JDK-6678999, “Stacktrace missing after null string comparisons”:
After comparing a string to null and catching the exception and repeating the operation, JVM starts throwing "stackless" NullPointerException (it occurs after 9000 loops but this is variable)
The evaluation of the issue is
When the server compiler compiles a method, the stack trace in an exception thrown
by that method may be omitted for performance purposes.
[…] If the user always wants stack traces, use the -XX:-OmitStackTraceInFastThrow option to the VM.
So, the option -XX:-OmitStackTraceInFastThrow may solve the issue.
Note that the bug report was against Java 6, but since it has been closed as “Won't Fix”, it may still be relevant, though you would have to replace “server compiler” with “c2 compiler” in the explanation now.
The use of NativeMethodAccessorImpl or GeneratedMethodAccessor… is not relevant to this issue, except that both have a common cause; a higher number of executions may trigger the optimizations.
BACKGROUND
I'm trying to build a map of earthquake events with data parsed from an RSS feed using the "Unfolding maps" library in Java (this is part of the Coursera course on OOP with Java). In theory, the data from the feed gets parsed into properties of the earthquake (location, magnitude, ...) which then form the basis for these marker objects that get displayed on a map. The libraries that are used are "Processing" and the "Unfolding Maps" library.
PROBLEM
Theres an "Unknown Source" error in the part, where I want to set the color property of the earthquake marker, depending on the magnitude of the event (ie. magnitude > 3 is "yellow").
Here's the error message:
Exception in thread "Animation Thread" java.lang.NullPointerException
at de.fhpotsdam.unfolding.marker.AbstractMarker.getProperty(Unknown Source)
at module3.EarthquakeCityMap.setup(EarthquakeCityMap.java:101)
at processing.core.PApplet.handleDraw(PApplet.java:2365)
at processing.opengl.PJOGL$PGLListener.display(PJOGL.java:873)
at jogamp.opengl.GLDrawableHelper.displayImpl(GLDrawableHelper.java:690)
at jogamp.opengl.GLDrawableHelper.display(GLDrawableHelper.java:672)
at javax.media.opengl.awt.GLCanvas$10.run(GLCanvas.java:1383)
at jogamp.opengl.GLDrawableHelper.invokeGLImpl(GLDrawableHelper.java:1277)
at jogamp.opengl.GLDrawableHelper.invokeGL(GLDrawableHelper.java:1131)
at javax.media.opengl.awt.GLCanvas$11.run(GLCanvas.java:1394)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
And here is the code
for (Marker marker:markers) {
if ((int) (marker.getProperty("magnitude")) > 3) {
System.out.println("trying to set the colour to yellow");
//marker.setColor(yellow);
}
}
The line with "setColor(yellow)" is commented out, as it seems that this is a problem of its own (may or may not have to do with it).
Anybody have an idea where this may come from and what I could read up on to better understand the problem? I'm pretty new to programming so any advice on how to learn the process of tracing errors / finding out the cause of a problem would be fantastic.
I have a NullPointerException in my application, that happens only on one specific PC, and is reproducible. I wrote my GUI using Javafx with some Swing JPanels on it via SwingNode.
What should I do?
Exception-Time = 2016-08-30 06:55:50 UTC Exception-Tag = 0 Exception-Message = Thread AWT-EventQueue-0 (Id = 55) throw exception: null Stack-Trace = java.lang.NullPointerException
at sun.swing.JLightweightFrame.updateClientCursor(Unknown Source)
at sun.swing.JLightweightFrame.access$000(Unknown Source)
at sun.swing.JLightweightFrame$1.updateCursor(Unknown Source)
at sun.awt.windows.WLightweightFramePeer.updateCursorImmediately(Unknown Source)
at java.awt.Component.updateCursorImmediately(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
More about the problem:
Apparently, this is a bug at the JDK itself (versions 8 and 9) and probably won't get fixed until JDK10.
This exception is thrown from within the sun.swing.JLightweightFrame.java class, at the updateClientCursor function (lines 472-749):
private void updateClientCursor() {
Point p = MouseInfo.getPointerInfo().getLocation();
SwingUtilities.convertPointFromScreen(p, this);
Component target = SwingUtilities.getDeepestComponentAt(this, p.x, p.y);
if (target != null) {
content.setCursor(target.getCursor());
}
}
In general, this is happening because MouseInfo.getPointerInfo() can return NULL, for example, when you move between graphic devices. 'MouseInfo' can still hold the former graphic device information, then getPointerInfo() can return NULL if the mouse already moved to the new graphic device and MouseInfo still didn't updated to the new graphic device information. this scenario will cause a Null Pointer Exception on this line MouseInfo.getPointerInfo().getLocation() for trying to run a method of a NULL object.
For me, NPE is thrown when I move my JavaFX app window between monitors on my multiscreen machine. Its not happening every time but it is reproducible very easily.
I'm using a Swing component in a JavaFX SwingNode component.
This bug is already a known issue at Oracle bug list.
Code Fix:
This snippet shows an optional fix for this bug:
private void updateClientCursor() {
PointerInfo pointerInfo = MouseInfo.getPointerInfo();
if (pointerInfo == null) {
/*
* This can happen when JavaFX cannot decide
* which graphics device contains the current
* mouse position.
*/
return;
}
Point p = pointerInfo.getLocation();
SwingUtilities.convertPointFromScreen(p, this);
Component target = SwingUtilities.getDeepestComponentAt(this, p.x, p.y);
if (target != null) {
content.setCursor(target.getCursor());
}
}
Taken from JetBrains repository
Optional solution:
Since it is a bug withing the formal Oracle JDK, there is no much I can do about it. there are fixes applied in other non-formal JDKs like OpenJDK for example, which applied a fix, but I don't know which version will apply this fix yet.
For me, I would probably try to compile and use my own JDK with the applied fix and use it in my project, but this is a hard to maintain and not so flexible solution. If someone have another fix/workaround I would be happy to hear.
I have noticed a strange problem with my program that I just can not figure out. I have included the method that has been flagged up, and the Error that was given. What's confusing me is that I have duplicated this method about 40 times on other buttons, changing only the 'engtf4' to another source where needed. They work perfectly with no errors, yet are written exactly the same. Adding further confusion, the method is executed exactly as intended(even though the error message below is given)?
I have looked around the net for similar problems using keywords - java.lang.NumberFormatException: For input string: "", I did however notice that all the example sites I saw had reference to a particular value in qoute marks. For example, -java.lang.NumberFormatException: For input string: "2345". I would appreciate any help I could get, thanks.
METHOD SOURCE CODE:
if (a.getSource() == engBuy4){
getItems();
q = engtf4.getText();
qq = Long.parseLong(q); //////////// LINE 13086
if (qq > 1000000 || total > 1000000){
Error.setText("You can ship a maximum of 1 million items.");
engtf4.setText("");
}
if (qq <= 1000000 && total <= 1000000){
if (qq > rem){
Error.setText("You can ship " + rem + " more items");
engtf4.setText("");
}
if (qq <= rem){
buyShrEng();
engtf4.setText("");
}
}
ERROR MESSAGE:
Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Long.parseLong(Unknown Source)
at java.lang.Long.parseLong(Unknown Source)
at DopeWars.DopeWars.mouseReleased(DopeWars.java:13086)
at java.awt.AWTEventMulticaster.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Long.parseLong() throws a NumberFormatException if the passed string is not a parsable long value. In your case, you are passing an empty string (probably because the user did not enter anything in the input field). You can verify this easily:
...
Long.parseLong("");
...
java.lang.NumberFormatException: For input string: ""
You should always be prepared to catch this exception (besides empty strings, the exception is thrown if the user enters anything which is not a Long), and show an appropriate error message to the user, something like
try {
qq = Long.parseLong(q);
} catch(NumberFormatException nfe) {
// show error message like "The string ... you entered is not a number."
...
}
If you want to treat an empty string as 0 (if that is reasonable for your use case), you can do something like (still requires the try/catch block to catch any other invalid inputs):
try {
long qq = 0;
if (q != null && !q.isEmpty()) {
qq = Long.parseLong(q);
}
...
} catch(NumberFormatException nfe) {
// show error message like "The string ... you entered is not a number."
...
}
In addition to that, instead of duplicating code dozens of times, you should check which are the variable parts of your code and replace them with variables, so that you can reuse the code instead of duplicating it.
It is raising the NumberFormatException, Since the argument passed to the parse() Method, is not parsable. What i mean to say is, input is invalid here.
Checkout the following link :)
http://docs.oracle.com/javase/7/docs/api/java/lang/Long.html
It seems that the value entered is an empty string :java.lang.NumberFormatException: For input string: ""
So before parsing to long you should test if the string value is empty or not.
In any ways you should catch the java.lang.NumberFormatException to put a default value if the parse doesn't succeed
We cannot parse empty space or null to long.If we try that,the number format exception arise.
so before parsing add the if statement to check the value is present or not.
if(q!=null && !"".equals(q))
qq=Long.parse(q);
It's good to use exception handling in these situations
Welcome, i am programming a simple RPG game in java applet. It is getting more and more complicated and many errors are thrown to my face. Today i have problem with .remove(); method.
Exception in thread "AWT-EventQueue-1" java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
at java.util.ArrayList$Itr.remove(Unknown Source)
at rpg.main.paint(main.java:365)
at rpg.main.update(main.java:331)
at sun.awt.RepaintArea.updateComponent(Unknown Source)
at sun.awt.RepaintArea.paint(Unknown Source)
at sun.awt.windows.WComponentPeer.handleEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
That's how error log looks like. Code of program:
main.java
As we can see error appears in paint methid in the end of program, but i dont know maybe it is caused by wrong initiation in the beginning of program?
public void initLocatables()
public void initLocatables2()
And i have to admit that they are called in main while loop in run method.
These is place where error apears, and below in comment i have included previous method that has also thrown error, both in remove();
for (Iterator i = locatablesArray.listIterator(); i.hasNext();) {
Locatable l = (Locatable) i.next();
l.draw(g);
i.remove();
}
/*while(itrLocatables.hasNext())
{
Locatable l = itrLocatables.next();
l.draw(g);
l.remove();
}*/
Thank you for any reply.
Maybe when you call repaint() in run(), paint() is queued to EDT and called as soon as possible; while iterating locatablesArray a call to initLocatables2() in run() is done another time and the re-init of locatablesArray in the same time the code of paint() will produce the error.
My advice is to separate init operation in a specific init section and call it once, the run your main loop.
Just another thing: why are you init a Iterator (class field itrLocatables) in initLocatables2()? Use iterator when needed if possible.
Hope to be clear, English is not my native language.
You cannot remove objects from a list/map while you are iterating them. That's the cause of the ConcurrentModificationException
i.remove();
If you will draw all the Locatable elements, and then clear the collection, maybe you should draw them all first, and then clear the collection, instead of removing them on the fly.
for (Iterator i = locatablesArray.listIterator(); i.hasNext();) {
Locatable l = (Locatable) i.next();
l.draw(g);
}
// Clear everything from the list
locatablesArray.clear();
java.util.ConcurrentModificationException
Another approach is to use a for loop through the locatablesArray starting at the end vs the beginning. That way any elements that are removed won't change the location of elements of the array that are yet to be scanned.