My app won't launch and points to a Null Pointer Exception on my FileReader fr. I initialized it as null to prevent a "Variable may not have been initialized" error. I know the file I want it to use is there under downloads. The file is also inside the main project folder and putting just "academiccalendar.json" does not work either.  My main activity:  public class MainActivity extends AppCompatActivity {   Event[] mobileArray; Gson gson = new Gson();  @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_main);      BufferedReader br;     FileReader fr = null;     try {         fr = new FileReader("C:/Users/Ali/Downloads/academiccalendar.json");     }     catch (FileNotFoundException e){         e.printStackTrace();     }     br = new BufferedReader(fr);     //br = new BufferedReader(new FileReader("C:/Users/Ali/Downloads/academiccalendar.json"));       mobileArray = gson.fromJson(br, Event[].class);   My logcat output:   12-31 20:06:37.368 9449-9449/com.example.test.testassigment E/AndroidRuntime: FATAL EXCEPTION: main java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.test.testassigment/com.example.test.testassigment.MainActivity}: java.lang.NullPointerException   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967)   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)   at android.app.ActivityThread.access$600(ActivityThread.java:127)   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)   at android.os.Handler.dispatchMessage(Handler.java:99)   at android.os.Looper.loop(Looper.java:137)   at android.app.ActivityThread.main(ActivityThread.java:4511)   at java.lang.reflect.Method.invokeNative(Native Method)   at java.lang.reflect.Method.invoke(Method.java:511)   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:976)   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:743)   at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.NullPointerException   at java.io.Reader.&lt;init&gt;(Reader.java:64)   at java.io.BufferedReader.&lt;init&gt;(BufferedReader.java:92)   at java.io.BufferedReader.&lt;init&gt;(BufferedReader.java:80)   at com.example.test.testassigment.MainActivity.onCreate(MainActivity.java:42)   at android.app.Activity.performCreate(Activity.java:4486)   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1052)   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1931)   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)    at android.app.ActivityThread.access$600(ActivityThread.java:127)    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)    at android.os.Handler.dispatchMessage(Handler.java:99)    at android.os.Looper.loop(Looper.java:137)    at android.app.ActivityThread.main(ActivityThread.java:4511)    at java.lang.reflect.Method.invokeNative(Native Method)    at java.lang.reflect.Method.invoke(Method.java:511)
129
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?
114399
How would you open a file (that has a known file/app association in the registry) into a "running instance" of the application it's supposed to open in? An example would be, I have Excel open and I click on an XLS file.....the file opens up in the current Excel instance. I want to do this for a custom application...how does the eventing/messaging work that "tells" the current instance that it needs to open a file? Is there a "file watcher" that looks for a request to do so etc? Thanks..
33241
I tried it and the errors are:  Exception in thread "main" java.awt.AWTError: Assistive Technology not found: org.GNOME.Accessibility.AtkWrapper at java.desktop/java.awt.Toolkit.newAWTError(Toolkit.java:472) at java.desktop/java.awt.Toolkit.fallbackToLoadClassForAT(Toolkit.java:488) at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183) at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:177) at java.base/java.util.HashMap$KeySpliterator.forEachRemaining(HashMap.java:1608) at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484) at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474) at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150) at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173) at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:497) at java.desktop/java.awt.Toolkit.loadAssistiveTechnologies(Toolkit.java:532) at java.desktop/java.awt.Toolkit.getDefaultToolkit(Toolkit.java:613) at java.desktop/javax.swing.UIManager.getSystemLookAndFeelClassName(UIManager.java:660) at com.cburch.logisim.gui.start.Startup.parseArgs(Startup.java:250) at com.cburch.logisim.Main.main(Main.java:32)   The error seems to be...     Caused by: java.lang.ClassNotFoundException: org.GNOME.Accessibility.AtkWrapper       at  java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:582)       at   java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:190)       at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)       at java.base/java.lang.Class.forName0(Native Method)       at java.base/java.lang.Class.forName(Class.java:374)       at java.desktop/java.awt.Toolkit.fallbackToLoadClassForAT(Toolkit.java:485)       ... 14 more     OUTPUT for  apt-cache policy logicsim logisim  logisim:   Installed: 2.7.1~dfsg-1   Candidate: 2.7.1~dfsg-1   Version table:  *** 2.7.1~dfsg-1 500         500 http://in.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages         500 http://in.archive.ubuntu.com/ubuntu bionic/universe i386 Packages         100 /var/lib/dpkg/status N: Unable to locate package logicsim   OUTPUT for update-java-alternatives -l  java-1.11.0-openjdk-amd64      1101       /usr/lib/jvm/java-1.11.0-openjdk-amd64 java-1.8.0-openjdk-amd64       1081       /usr/lib/jvm/java-1.8.0-openjdk-amd64
121551
I have a function called:  void initializeJSP(string Experiment)   And in my MyJSP.h file I have:  2: void initializeJSP(string Experiment);   And when I compile I get this error:     MyJSP.h:2 error: variable or field initializeJSP declared void   Where is the problem?
47126
When trying to upload a picture from my phone, the Android app crashes a few different ways, depending on whether I select the Gallery or Photos image source. (Uploading by manually entering a URL works perfectly.) The problem occurred using beta versions 1.0.63, 1.0.71, 1.0.72, and now 1.0.73, on a Samsung Galaxy S4 running Android 4.1.2.  These are the steps which I've used:   Open an Ask/Answer a Question window, enter a sentence. Click on the picture icon, which opens a "Choose Image Source" window. Select "From Device," which opens a window offering a choice of "Gallery" or "Photos."   If I select Gallery, when the pictures open, choosing one causes the app to immediately crash. The circle goes around for about 15 seconds (see picture on left below), then re-opens to the Ask a Question window, where the original text is still visible. The camera icon isn't live (it's grayed-out), so trying to post again in that window is not an option.   If I select Photos, when the pictures open, I can choose one. It pauses, which I interpret as an effort to post. After about 10 seconds, however, the app crashes to the feed screen, and an error message in a black box appears which says "Unfortunately, the process com.stackexchange.marvin has stopped." (See picture on right below.) There are Report and OK options under the error message. Initially I was able to get a screenshot, however the message disappeared before I could select Report, then the app crashed. However, on 8/11/15, and a few times since, I've been able to submit a report before the crash.  Update 9/2/15: With version 1.0.72, the error message varied, and many tries produced a picture a few times. There was no indication as to when or why it would happen, and each of those times, the picture posted sideways. With version 1.0.73, the error message has returned to the original, and fifty tries have not produced a posted picture from either Gallery or Photos. I'm updating this report in the hope that others are experiencing the same problem, or to be notified if the developers are aware of it. Thanks!
81222
In my Java app I need to get some files and directories. This is the program structure: ./main.java ./package1/guiclass.java ./package1/resources/resourcesloader.java ./package1/resources/repository/modules/   -&gt; this is the dir I need to get ./package1/resources/repository/SSL-Key/cert.jks    -&gt; this is the file I need to get  guiclass loads the resourcesloader class which will load my resources (directory and file). As to the file, I tried resourcesloader.class.getClass().getResource(&quot;repository/SSL-Key/cert.jks&quot;).toString()  in order to get the real path, but this way does not work. I have no idea which path to use for the directory.
61737
I would like to use Class.newInstance() but the class I am instantiating does not have a nullary constructor. Therefore I need to be able to pass in constructor arguments. Is there a way to do this?
70680
I was loading an image resource with the following code and it works fine from my dev environment (netbeans) but threw an exception as soon as it ran from the desktop.  new ImageIcon(Images.class.getResource("images/highlighter24.gif"));   I traced it down to my file having different case than in the code.  Fine, my bad, but why the inconsistent behavior?  Gremlins?  Note: I'm running on windows before you ask.
90464
We noticed that lots of bugs in our software developed in C# (or Java) cause a NullReferenceException.  Is there a reason why "null" has even been included in the language?  After all, if there were no "null", I would have no bug, right?  In other words, what feature in the language couldn't work without null?
93347
I still have a problem with the splash screen. I don't want to use the property SC.TopMost=true.  Now my application scenario is as follows:  in progeram.cs:  [STAThread] static void Main() {     new SplashScreen(_tempAL);// where _tempAL is an arrayList     Application.Run(new Form1(_tempAL)); }   in SplashScreen class:  public SplashScreen(ArrayList _Data) {     DisplaySplash() }  private void DisplaySplash() {     this.Show();     this.TopMost = true;     this.CenterToScreen();     this.SetTopLevel(true);      _allServerNarrators = new string[10];     for (int i = 0; i &lt; _allServerNarrators.Length; i++)         _allServerNarrators[i] = null;      GetFromServer();      this.Hide();     _serverData = new ArrayList();     _thisData.Add(_allServerNarrators);     _thisData.Add(_serverNarrators);  } private void GetFromServer() {     _serverNarrators = new ArrayList();     string _file = "Suras.serverNar";      if (!Directory.Exists("c:\\ASGAQuraan"))         Directory.CreateDirectory("c:\\ASGAQuraan");      while (counter &lt; 4 &amp;&amp; _serverFiles == null)     {         if (Download("c:\\ASGAQuraan", _ftpServerIP, _file))         {             StreamReader _strReader = new StreamReader                          ("c:\\ASGAQuraan\\"+_file,System.Text.Encoding.Default);             string _line = _strReader.ReadLine();             string _word;              while (true)             {                 while (_line != null)                 {                     _word = _line.Substring(0, _line.IndexOf("*"));                     int _narId = Convert.ToInt32(_word);                     _line = _line.Substring(2);                     int k = 0;                     _serverNarratorNode = new ArrayList();                     while (true)                     {                         int ind = _line.IndexOf("*");                         if (ind &gt; 0 &amp;&amp; ind &lt; _line.Length)                         {                             string str = _line.Substring(0, (ind));                             if (k == 0)                             {                                 _allServerNarrators[_narId] = str;                                 _serverNarratorNode.Add(str);                             }                             else                             {                                 _serverNarratorNode.Add(str);                             }                             _line = _line.Substring(ind + 1);                             k++;                         }                         else                         {                             _line = null;                             break;                         }                     }                     _serverNarrators.Add(_serverNarratorNode);                     _serverFiles = "added";                 }                 _line = _strReader.ReadLine();                 if (_line == null)                 {                     break;                 }             }         }         else             counter++;     } }   What I want is something in the splash screen class which waits until the thread finishes.  For more details, please tell me what I need to tell you.
77081
I downloaded the eclipse from its site. And extracted in home folder. For the first time when I opened it, it worked fine. Then I locked it to launcher. Now it's not starting when I click on launcher icon in eclipse but it starts when I start it from the folder where I extracted it. Please tell some way to keep it in launchcer and open it from t here only.  Thanks.  [Desktop Entry] Encoding=UTF-8 Version=1.0 Type=Application Name=Java - SnapdealOMS/src/main/java/com/snapdeal/oms/admin/web/controller/ReloadCacheController.java - Eclipse  Icon=eclipse.png Path=/home/nakulkumar/Downloads/eclipse Exec=/usr/bin/java -Dosgi.requiredJavaVersion=1.6 -XX:MaxPermSize=256m -Xms40m -Xmx512m -jar /home/nakulkumar/Downloads/eclipse//plugins/org.eclipse.equinox.launcher_1.3.0.v20140415-2008.jar -data /home/nakulkumar/Snapdeal_workspace -os linux -ws gtk -arch x86_64 -showsplash /home/nakulkumar/Downloads/eclipse//plugins/org.eclipse.platform_4.4.0.v20140925-0400/splash.bmp -launcher /home/nakulkumar/Downloads/eclipse/eclipse -name Eclipse --launcher.library /home/nakulkumar/Downloads/eclipse//plugins/org.eclipse.equinox.launcher.gtk.linux.x86_64_1.1.200.v20140603-1326/eclipse_1605.so -startup /home/nakulkumar/Downloads/eclipse//plugins/org.eclipse.equinox.launcher_1.3.0.v20140415-2008.jar --launcher.appendVmargs -exitdata 34000f -product org.eclipse.epp.package.java.product -vm /usr/bin/java -vmargs -Dosgi.requiredJavaVersion=1.6 -XX:MaxPermSize=256m -Xms40m -Xmx512m -jar /home/nakulkumar/Downloads/eclipse//plugins/org.eclipse.equinox.launcher_1.3.0.v20140415-2008.jar StartupNotify=false StartupWMClass=Eclipse OnlyShowIn=Unity; X-UnityGenerated=true
61801
I'm new to Ubuntu, using 18.04 and trying to install Netbeans or Eclipse but neither of them works.  At first my java was version 10. Searching for solutions I found many suggestions to install version 8 so I installed that and changed my default java to 8, but I'm getting new errors.  Here is the error of eclipse which is in its configuration folder (after running eclipse from terminal, eclipse guided me there to see the error):  !SESSION Sat Jun 09 15:21:19 CEST 2018 ----------------------------------------- !ENTRY org.eclipse.equinox.launcher 4 0 2018-06-09 15:21:19.382 !MESSAGE Exception launching the Eclipse Platform: !STACK java.lang.ClassNotFoundException: org.eclipse.core.runtime.adaptor.EclipseStarter     at java.net.URLClassLoader.findClass(URLClassLoader.java:381)     at java.lang.ClassLoader.loadClass(ClassLoader.java:424)     at java.lang.ClassLoader.loadClass(ClassLoader.java:357)     at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:626)     at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)     at org.eclipse.equinox.launcher.Main.run(Main.java:1438)     at org.eclipse.equinox.launcher.Main.main(Main.java:1414)   Netbeans doesn't even give error messages - it just can't load.  Again I searched to see what is wrong it seems these applications even need older versions of java but I can't find any older version. (java doesn't support them)  Can someone please help?
61815
I read the Java tutorials on Sun for JAR files, but I still can't find a solution for my problem. I need to use a class from a jar file called jtwitter.jar, I downloaded the file, and tried executing it (I found out yesterday that .jar files can be executed by double clicking on them) and Vista gave me an error saying "Failed to load Main-Class Manifest attribute from [path]/jtwitter.jar".  The guy who coded the .jar file wants me to import it, but where do I store the .jar file to import it in my code? I tried putting both the .jar file and my .java file in the same directory, didn't work.  The file I'm trying to work for is here:   I'm using JCreator LE.
16225
Why does it (apparently) make a difference whether I pass null as an argument directly, or pass an Object that I assigned the value null?  Object testVal = null; test.foo(testVal);    // dispatched to foo(Object) // test.foo(null);    // compilation problem -&gt; "The method foo(String) is ambiguous"     public void foo(String arg) { // More-specific     System.out.println("foo(String)"); }  public void foo(Object arg) { // Generic     System.out.println("foo(Object)"); }   In other words, why is the (commented-out) second call to foo(...) not dispatched to foo(Object)?  Update: I use Java 1.6. I could compile Hemal's code without problems, but mine still doesn't compile. The only difference I see is that Hemal's methods are static while mine are not. But I really don't see why this should make a difference...?  Update 2: Solved. I had another method foo(Runnable) in my class, so the dispatcher couldn't unambiguously select the single most specific method. (See my comment in Hemal's second answer.) Thanks everyone for your help.
121055
I downloaded some 3D games, unzipped them and got .jar files. How can I use these in Android?  I have a Galaxy S running 2.1.
121233
I'm trying to run an application downloaded from the internet (e.g., Jabref) but it seems that it fails silently. When I try to open it by double clicking it, nothing happens. When I use the terminal I get the following message:     LSOpenURLsWithRole() failed with error -10810 for the file .../xxxx.app   I tried several suggestions that I found here like changing permissions and modifying the Info.plist file, but nothing works.  Because it's a Java application, I tried to run it through terminal using      java -cp "CLASSPATH" MAINCLASS    and it works fine.  Just to mention that I get this error not only with this app, but for a few other applications.  Thanks in advance.
72722
getRealPath() is returning the actual path in the local system, but returns null when deployed with a .war file.  &lt;%@ page import="java.io.*" %&gt; &lt;%@ page contentType="text/html;charset=ISO-8859-1" %&gt;  &lt;% int iLf = 10; char cLf = (char)iLf; String a= application.getResource("/"); //String myfile = application.getRealPath("/")+ "generate.xml"; //String myfile = request.getContextPath()+"generate.xml"; //String myfile = request.getRealPath("/")+"generate.xml";  out.println(myfile);     File outputFile = new File(myfile); outputFile.createNewFile(); FileWriter outfile = new FileWriter(outputFile); outfile.write(" &lt;?xml version='1.0' encoding='UTF-8'?&gt; "+cLf); outfile.write(" &lt;playlist version='1' xmlns = 'http://xspf.org/ns/0/' &gt; " +cLf); outfile.write(" &lt;title&gt;My Band Rocks Your Socks&lt;/title&gt; "+cLf);  outfile.write("&lt;trackList&gt;"+cLf);  %&gt;  &lt;%! String[] sports; %&gt;  &lt;%     sports = request.getParameterValues("sports");      out.println("&lt;html&gt;&lt;body&gt;&lt;h1&gt;hello&lt;/h1&gt;&lt;/body&gt;&lt;/html&gt;");      if (sports != null)     {           for (int i = 0; i &lt; sports.length; i++)          {                // outfile.writeln (sports[i]);                String total=sports[i];               String[] sa=total.split("[,]");               // String[] sub=new String();               outfile.write("&lt;track&gt;"+cLf);               for (int j=0;j&lt;sa.length;j++)               {                 // outfile.writeln(sa[j]);                 // outfile.writeln("sa["+j+"]="+sa[j]);                 if( j == 0)                 {                      outfile.write("&lt;location&gt;" + sa[0] +"&lt;/location&gt;"+cLf);                  }                 else if (j == 1)                      {                         outfile.write("&lt;image&gt;" + sa[1] +"&lt;/image&gt;"+cLf);                       }                      else if( j==2)                           {                             outfile.write("&lt;title&gt;" + sa[2] +"&lt;/title&gt;"+cLf);                           }                 }// end of inner for loop()                       outfile.write("&lt;/track&gt;"+cLf);          //outfile.writeln();       }// end of outer for()     }      //else outfile.writeln ("&lt;b&gt;none&lt;b&gt;");    outfile.write(" &lt;/trackList&gt; "+cLf);   outfile.write(" &lt;/playlist&gt; "+cLf);   outfile.close();    %&gt; &lt;object type="application/x-shockwave-flash" width="400" height="170"           data="xspf_player.swf?playlist_url=generate.xml"&gt;           &lt;param name="movie" value="xspf_player.swf?playlist_url=generate.xml" /&gt;  &lt;/object&gt;   Can anyone provide me with an alternative for this? It would be very helpful if you showed some sample code too.