I'm running into the strangest error in this program, which is confirmed when debugging it. I have the following code (boiled down to highlight the problem, of course):
BHFrame.java
public class BHFrame
{
private boolean uSS;
private StateSaver stateSaver;
public BHFrame(boolean useInternalStateSaver)
{
//Init code
uSS = useInternalStateSaver;
//More init code
System.out.println(uSS);
if (uSS)
{System.out.println("Entered 1");
stateSaver = new StateSaver(title, false);
stateSaver.addSaveable(getThis());
}
//More init code
System.out.println(uSS);
if (uSS)
{System.out.println("Entered 2");
try
{
stateSaver.loadState();
stateSaver.putState(getThis());
}
catch (IOException ex)
{
alertUserOfException(ex);
}
}
}
}
GUI.java
public class GUI extends BHFrame
{
public GUI(boolean useInternalStateSaver)
{
super(useInternalStateSaver);
}
}
Main.java
public class Main
{
public static void main(String[] args)
{
GUI gui = new GUI(false);
}
}
Output
false
false
Entered 2
Exception in thread "main" java.lang.NullPointerException
at bht.tools.comps.BHFrame.<init>(BHFrame.java:26)
at bhms.GUI.<init>(GUI.java:5)
at bhms.Main.main(Main.java:5)
The class BHFrame is extended and run from a child class that calls this constructor, but that really shouldn't affect this behavior. The problem is that, when false is passed to the constructor as useInternalStateSaver, the first if (uSS) is skipped, but the second is entered. Upon debugging, I found that uSS is false throughout runtime, including on the line of the second if statement, here. Why would Java enter an if statement when the condition returns false? Before you ask, I did delete the .class files and recompile it just in case there was some residual code messing with it, but I got the same result. And rest assured, all the references to the uSS variable are displayed here.
Solution
As it turns out, this appears to be a bug in NetBeans 7.1 Build 201109252201, wherein the IDE doesn't properly insert new code into the compiled .class files. The problem was fixed by compiling the files externally. A bug report has been submitted.
Whatever's throwing that exception is probably not in your posted code.
It's not being caught by your catch statement, which only catches IOException.
It's a NullPointerException and can occur anywhere.
You have shown no indication that the code inside your if block is actually executing. In your screenshot, there is absolutely know way of knowing if your if block is entered or not. There are no logging statements.
Add debugging messages at various points to see exactly what is happening. Or, you know, look at line 26 (wayyyyy before your posted code) to see why you're getting a NullPointerException.
I've seen crazy stuff like this when there is bad RAM on the machine. You might want to run memtest86.
You might also consider deleting all of your project class files, and then doing a build. Maybe you changed Main.java, but it was never recompiled. I hate that when that happens.
This is just a guess, because I can't see the code you are mentioning, but I reckon you have defined a local variable uSS in the second //More init code segment.
Once you define a local variable named the same as an instance variable, it 'hides' the instance variable. Better to qualify all instance variables with this.
So, try qualifying all above accesses of uSS with this. ... (this.uSS)
Even if this isn't the issue, it might be better to post the full code anyway.
HTH
Related
I am working on Android app and we are working as a team. I am facing a serious issue. And that is when ever I try to get the data from intent it gives me following exception
Parcel android.os.Parcel#355932a: Unmarshalling unknown type code
4784211 at offset 712
I know on SO there are a lot of helping material related to this issue, but my case is different and quiet mind boggling .....
Here is a quick code to see how I am getting my object
try {
if (data.hasExtra("KEY_MY_MODEL")) {
MyCustomModel newSelectedModel = data.getParcelableExtra("KEY_MY_MODEL");
//DO SOME THING WITH OBJECT
}
} catch (Exception e) {
e.printStackTrace();
}
Case1:
I am getting exception on first line if (data.hasExtra("KEY_MY_MODEL")) {
and this is quiet funny because when I inspect the intent object (data) while debugging and if I look into intent object using debugging I can see all my custom object.
The keys of getting object are same, if in any case the key is wrong I think the code inside the if condition must not get run. as it will return false.
But instead of returning false it is giving the above mentioned exception.
Case2: As I told you we are working in team, the same set of code is running perfectly on other system, but when I run app from my system and install app on device, it is giving the exception I mentioned above.
This is very much frustrating. I think there is something wrong with proguard, as I read on S.O but its still not helpful. Any Idea why this is happening? This looks like a big bug.
Note: I am using A.S 3.5 and on other system A.S 3.5 is in use, even we have same set of sdk, configurations and other things are quiet
identical on both sides...
It seems to be a ProGuard issue
Just add this line in proguard.rules.pro/txt
-keepclassmembers class * implements android.os.Parcelable {
static ** CREATOR;
}
I'm writing a private method in Java that reads and write to a simple text file, which it should make if it doesn't exist since createNewFile() checks for that first.
private boolean updateGameQuota(String name, String quantity) {
...
File quotaLog = new File("seller-quotas.txt");
quotaLog.createNewFile();
...
return ret;
}
The compile-time error is: SmsFunctions.java:256: error: unreported exception IOException; must be caught or declared to be thrown
quotaLog.createNewFile();
^
1 error
Placing it in a try-catch block doesn't seem to be the issue, as I tried that (also on many other lines that try passing quotaLog) but eventually I get to a point where it's clear that something else is wrong. The File object is fine, but then if I try to use createNewFile or say
FileReader sQReader = new FileReader(quotaLog);
I get a FileNotFoundException even though the file is definitely there and I tried this on other text files which are read elsewhere successfully with the same result.
Any help or ideas would be greatly appreciated!
Update:
So in the end my issue was indeed just putting try-catch blocks around everything and making sure variables set within them were first created outside of those blocks. My confusion came from a false sense of sureness that fileraders/filewriters shoulnd't need try catch blocks (I could swear I've used them without many times) and the error was actually an indication of something else.
Perhaps before closing the thread someone could elaborate as to why Java doesn't always make a fuss about it, if that's true?
Thanks!
File.createNewFile() can throw an IOException (a checked exception) and needs to be surrounded in a try-catch block or the method you're using it in needs to be declared as throws IOException and you need to handle it upstream.
To debug the FileNotFoundException, you could try:
File quotaLog = new File("seller-quotas.txt");
System.out.println(quotaLog.getAbsolutePath());
Which uses the File.getAbsolutePath() method to print where it expects the file to exist.
The following code segment:
private class ConnectionControl implements Runnable
{
public void run()
{
while( true )
{
if( !cnnct.isInMsgEmpty() )
System.out.println( "Incoming message: " + cnnct.getInMsg().getPayloadString() ) ;
}
}
}
Works when I run it in eclipse debugger and place a breakpoint at the System.out line. However, if I run it normally I don't get the "Incoming message..." output.
Any thoughts on why this would be or how even to debug it???
Ahh figured it out... had a deadlock situation going on where two threads were using the same resource. Thanks for your help guys!
Cheers!
There are multiple ways to invoke Java code, depending on where you need it.
What you have shown is not enough to be self-standing, and should cause an error if you try to invoke it as an applet or a java application (java .... ConnectionControl). It may be that Eclipse can invoke a Runnable - I have not seen it though.
Try
making the class public
add a static main method making it a Java application
put a message in the start of the main method so you can see it is invoked
You're already using System.out.println for your program output. Add some sysouts that output where you are in the code and the status of various variables.
I don't know how this is being called but from the code I see your if condition is always evaluating false.
I created a method and keep getting an error that I need to include a } at the end of my method. I put the } in and the error is still there! If I then delete that } the same error will pop up on a prior method; and that error wasn't there before. in other words, if i type the } on my most recent method then the error stays there and only there. if i delete it, it duplicates that error on my prior method.
private void putThreeBeepers() {
for (int i = 0; i < 2; i++) {
putBeeper();
move();
}
putBeeper();
}
private void backUp() {
turnAround();
move();
turnAround();
}
You really want to go to the top of your file and do proper and consistent indention all the way to the bottom.
For example...
private void putThreeBeepers()
{
for (int i = 0; i < 2; i++) {
putBeeper();
move();
}
putBeeper();
}
private void backUp()
{
turnAround();
move();
turnAround();
}
Odds are, somewhere along the line, you are missing a }. Your description isn't super clear, but if the code you posted is how you actually have it formatted in your file then odds are you just missed something somewhere... and poor indentation makes it very hard to spot.
The fact that the message is changing is confusing, but it is the sort of thing you see in these cases.
the error might be misleading. In my case i had incorrect/incomplete comment statements such as below which is broken lead to this error:
/*
// */
*/
Fixing the comments fixed the error. Hope this helps. Thanks.
I think this can be caused by a number of different problems. :(
In my case it was that I have forgotten to specify the type of two parameters in one of my methods declareations.
To fix I had to change this:
onUpgrade(SQLiteDatabase pDb, pOldVersion, pNewVersion)
{
}
to this:
onUpgrade(SQLiteDatabase pDb, int pOldVersion, int pNewVersion)
It might be due to invisible Chars when copying code from PDF ebook.
Be careful of the little red dot '.'
Choose 'Select First Character' -> then delete it.
Also, the same error might occur if you accidentally write an if-statement outside of a method. I kept overlooking it since I was looking at the bracket-matching only.
I just simply add another"}",makes as "}}",then problem solved
I didnt have to put anther "}" for my other java code exercise.
Im a java beginner,I've come across same problem so I searched online found this thread.Hope this help
Had the same problem. Turned out to be a very fundamental oversight.
I was having the properties of a class declared like this:
private Texture foo;
private Sprite bar;
foo = new Texture();
bar = new Sprite();
The mistake was i had been instantiating the foo and bar variables outside the functions
of the class. When I put the
foo = new Texture();
bar = new Sprite();
into their proper functions (like below), the error went away.
private Texture foo;
private Sprite bar;
// function
public void instantiateVariables(){
foo = new Texture();
bar = new Sprite();
}
I got this error due to a missing <%.
Here are the steps.
Just copy paste your code in notepad
Remove copy from Java file
Again copy notepad and paste into Java file.
An error will be gone.
This question have already accepted answer but still there are some other problems where it occurs (like even though all statements are there correctly sometimes we will get this issue) and there are solutions too.
Recently I came across like this situation in eclipse workspace.
The solution is
Take the back up of that java file.
Remove the java file from that location and do the build/compile
Paste the file in the same location and do the build/compile
If the above step 3 does not work create new file and paste the content/code from backup file and do the build/compile
If the above step 3&4 both are not working then type the code of that file manually end-to-end and do the build/compile
If this error comes in jsp, look for the braces. if open or close braces are missing, we will get this error.
I'm getting a NullPointerException in a Nokia S40.
I want to know what is causing this exception.
The device shows:
NullPointerException java/lang/NullPointerException
This error only occurs in the device, running in the emulator the application works fine.
I use microlog to debug my application. But the application works fine if the log is enabled.
Is there a way to get the stack trace when I get this NullPointerException? I don't need all details like the line number just which method cause this exception.
UPDATE: I installed the same application in another Nokia S40 and the same error didn't occur.
Nokia 2660 - error
Nokia 6131 - no error
UPDATE 2: Somehow I find what was causing the NullPointerException.
import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Graphics;
public class OuterClass extends Canvas {
private Config config;
public OuterClass() {
this.config = new Config();
}
public void paint(Graphics graphics) {
HelperClass helper = new HelperClass(this.config);
helper.doStuff();
}
public void dispose() {
this.config = null;
}
public class Config implements IConfig {
public int getSomething() {
// ...
}
}
}
public class HelperClass {
private IConfig config;
public HelperClass(IConfig) {
this.config = config;
}
public doStuff() {
config.getSomething(); // Here is thrown NullPointerException
}
}
In some situations a thread is started and call the OuterClass.dispose() before the helper.doStuff() causing the NPE. I think when I enabled the log it made the thread slower and helper.doStuff() was called when I expected it to be called.
You are not going to find any way to save a Throwable stack trace on a Nokia Series40 handset.
The usual brute force way of debugging JavaME application on Series40 is to modify your code to create a stack trace yourself in memory.
What I'm talking about is:
Each Thread that you can identify (including system callback threads) needs its own Stack object, containing strings. Obviously, this increases the memory footprint of your application somewhat but keeping it in memory should limit the impact on race conditions.
When your code enters a method, it adds the method signature to the current Thread Stack. When the method exits (and you better only have one exit point per method) it pops the top of the Stack.
You can add aditional debug info on the stack, like values of variables in different places of the code.
You don't necessarily need to add this to every single method in your code.
You can add try{}catch(Throwable){} to the entry point of every thread you identified and either dump the stack in a file or on the screen (in a Form).
Obviously, this is not the kind of change you want to manually add in a lot of places in a large existing codebase. You can however make it part of your organisation coding standards for the future and write a source code parsing script to automatically add it to existing code.
I had some trouble in the past trying to print the stack trace to somewhere else than the standard output. The standard exception class doesn't provide the printStackTrace method that receives the output stream, therefore it only prints to the standard output stream.
It's possible, at least in Java SE, to redirect the java output stream to somewhere else by simply saying that System.out = . The PrintStream class receives an OutputStream, which means that you could create your own ByteArrayOutputStream, initialize a PrintStream, sets System.out to that stream, and then call ex.printStackTrace(). I don't have a J2ME environment here but I believe that, as long as it won't break when you try to set System.out to something else (nothing says that it's readonly in the docs), you should be able to do it.
After you do that, I would recommend writing it to a RecordStore that you have specifically for that, and then upload the records of that RecordStore to your server so you can get it.
I know it's not very easy but it may work. I would first test the System.out thing. If it works, everything else should work too.
My answer was wrong. As pointed out, the System.out and System.err fields are declared final. If you can't get the stack trace, and if you can't get the error when running the application on your emulator, try creating trace bullets on your code (alerts, logs, whatever you can) to isolate the piece of code where the problem is happening. It has to be something that could change between the emulator and the real device - for example, something related to retrieving/ saving records in a RecordStore, opening a Connection, etc... What did you try to do when you had the problem?
You could use Microlog to send an e-mail when the exception occurs.
Microlog
You could try catching the exception in some high-level try/catch block and then emailing the trace to yourself.