please help me.i write this code :  public class MainActivity extends AppCompatActivity {      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         File dir=Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);         File[] files=dir.listFiles();         Toast.makeText(this,files.length+"",Toast.LENGTH_LONG).show();      } }   and it has this error :  Caused by: java.lang.NullPointerException     at ir.itpro.videosample.MainActivity.onCreate(MainActivity.java:20)   i put 3 files in directory downloads .  how to fix it now??
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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?
59807
How can I get crash data (stack traces at least) from my Android application? At least when working on my own device being retrieved by cable, but ideally from any instance of my application running on the wild so that I can improve it and make it more solid.
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I used   Runtime.getRuntime().exec("_____")   but it throws a IOException as below:  java.io.IOException: CreateProcess: c:/ error=5   at java.lang.Win32Process.create(Native Method)   at java.lang.Win32Process.&lt;init&gt;(Win32Process.java:63)   at java.lang.Runtime.execInternal(Native Method   I don't know whether I have the problem with specifying the path or something else. Can anyone please help me with the code.
113807
Why does the following code not work?  I want to instantiate prefabs in a list and then use  it as a GameObject like that :  public GameObject prefab;  void Start() {   ArrayList players = new ArrayList();    for(int i=0; i&lt;5; i++)   {         players.Add( (GameObject)Instantiate(prefab));   }    players[2].transform.position = new Vector3(1, 1, 1);  }   there is an error message
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My below test fails because of Run Failures: TestRangehoodObjectionSheet.RangehoodObjectionSheetTest Methods defined as TestMethod do not support getContent call. I added the Blob thinking it might resolve but it doesn't work. What could be the problem here? Have I used the Blob correctly?  @isTest public with sharing class TestRangehoodObjectionSheet {      static testMethod void RangehoodObjectionSheetTest() {             String Build                = NBATRecords.getIdFromDeveloperName('Plan_Reviews__c','Building_Plan_Review');             Account a = new Account(Name = 'Test1' ,Type = 'Lead Acct',BillingState = 'CA',Industry = 'Business Services');             insert a;              Establishment_Record__c er = new Establishment_Record__c(Account__c=a.Id ,Project_Name__c = 'TestPreet',PremiseStreet__c='Manhattan ave',PremiseBorough__c='Manhattan',PremiseState__c='NY',PremisePostalCode__c='11102',Referral_Source__c='311',Data_Source__c='CAMIS',Phase__c='Initiate',Business_Status__c='Open' );             insert er;              Application__c ap = new Application__c(Establishment_Record__c=er.Id,Job_Number__c='222222222');             insert ap;              Plan_Reviews__c pr = new Plan_Reviews__c(Application__c =ap.Id ,DOB_Job_Number__c='222222222',RecordTypeId =Build,Objections__c='Pipe size not indicated');             insert pr;             PageReference pageRef = Page.RangehoodObjectionSheet;              Test.setCurrentPage(pageRef);               Blob content = Test.isRunningTest() ? Blob.valueOf('UNIT.TEST') : pageRef.getContent();              Plan_Reviews__c              p   = new Plan_Reviews__c(id=pr.Id);                ApexPages.StandardController sc  = new ApexPages.standardController(p);             System.assertNotEquals(sc,null);             RangehoodObjectionExtention    ext = new RangehoodObjectionExtention(sc);              ext.Savecopy();       } }   Actual class for the test:  public with sharing class RangehoodObjectionExtention { private final ApexPages.StandardController controller; private final Id                           planreviewID; public String imageURL{get;set;} public List&lt;String&gt; objlist {get;set;}  public string currentdate {get; set;}    public RangehoodObjectionExtention (ApexPages.StandardController stdController) {         controller   = stdController;         planreviewID = (Id)controller.getRecord().get('Id');         Date dt = Date.today();         currentdate = dt.format();         list&lt;Plan_Reviews__c&gt; prlist = [select FDNY_Objections__c from Plan_Reviews__c where id = :planreviewID limit 1];         string obj;         for(Plan_Reviews__c pr: prlist){            obj = pr.FDNY_Objections__c;             }         if(obj!=null){            list&lt;string&gt; objections = obj.split(';');             integer i =1;            objlist = new list&lt;string&gt;();            for(string o : objections){               objlist.add(i++ +'. '+o);            }         }         imageURL='/servlet/servlet.FileDownload?file=';         List&lt; document &gt; documentList=[select name from document where Name='RangehoodObjectionLogo'];         if(documentList.size()&gt;0)         {            imageURL=imageURL+documentList[0].id;         }       }          public PageReference Savecopy(){       PageReference p = Page.RangehoodObjectionSheet;       blob b = ApexPages.currentPage().getContentAsPDF ();       Attachment a = new Attachment();       a.body = b;       a.name = 'Rangehood Objection sheet Issued '+currentdate+'.pdf';       a.parentid = planreviewID;        insert a;        PageReference pref = new PageReference('/'+planreviewID);       return pref;    } }
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I've recently searched how I could get the application's directory in Java. I've finally found the answer but I've needed surprisingly long because searching for such a generic term isn't easy. I think it would be a good idea to compile a list of how to achieve this in multiple languages.  Feel free to up/downvote if you (don't) like the idea and please contribute if you like it.  Clarification:  There's a fine distinction between the directory that contains the executable file and the current working directory (given by pwd under Unix). I was originally interested in the former but feel free to post methods for determining the latter as well (clarifying which one you mean).
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i am building a app which takes input from user and then search to a remote database(MySql).And then display the retrieved data on VisualForce page.One important note that my app will be distributable.  here is my controller class  public with sharing class Search  {    public String strTag {get;set;}   public String strlocation {get;set;}    public PageReference find() {              return null;   } }   Thanks in advance.  Updated  public with sharing class Search  {   public String strTag {get;set;} public String strlocation {get;set;}   public PageReference find() {             HttpRequest req = new HttpRequest();   HttpResponse res = new HttpResponse();   Http http = new Http();    req.setEndpoint('https://localhost/salesforce/');   req.setMethod('POST');     req.setCompressed(false);   req.setBody('key1=value1&amp;key2=value2');   req.setHeader('Content-Type', 'application/x-www-form-urlencoded');      try {     res = http.send(req);   } catch(System.CalloutException e) {     system.debug('Callout error: '+ e);   }   system.debug(res.getBody());      return null;  } }   I am getting below error now      error message System.CalloutException: Unauthorized endpoint, please check Setup->Security->Remote site settings. endpoint = localhost/salesforce
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Check out the below program.   try {     for (String data : Files.readAllLines(Paths.get("D:/sample.txt"))){         String[] de = data.split(";");         System.out.println("Length = " + de.length);     } } catch (IOException e) {     e.printStackTrace(); }   Sample.txt:   1;2;3;4 A;B;; a;b;c;   Output:   Length = 4 Length = 2 Length = 3   Why second and third output is giving 2 and 3 instead of 4. In sample.txt file, condition  for 2nd and 3rd line is should give newline(\n or enter) immediately after giving delimiter for the third field. Can anyone help me how to get length as 4 for 2nd and 3rd line without changing the condition of the sample.txt file and how to print the values of de[2] (throws  ArrayIndexOutOfBoundsException)?
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I have samsung galaxy 3 (I5801). I have downloaded many APK files from internet. I have no problem in installing APK files. By default when APK file is selected it installs itself to phone memory. I want it to install application on SDCARD. I have made my phone memory full.   So my queries are   How to install APK on SDCARD? APK should install itself to SDCARD. How to move already installed application to SDCARD from phone memory?
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This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, navigate to the  tag. This question and answer is owned by the community! If you can improve it and make it more useful, you're welcome to edit it. I am building a trigger, a unit test, or other Apex code. I'm working with sObject records, and trying to access related record information. For example, I might have a structure like this: Account a = new Account(Name = 'Test'); insert a;  Opportunity o = new Opportunity(Name = 'Donation', AccountId = a.Id); insert o;  System.assertEquals(o.Account.Name, 'Test', 'Correct Account associated'); // Assertion fails!  Or, in a trigger, I might be aiming for something like this: trigger ContactTrigger on Contact (after insert) {     for (Contact c : Trigger.new) {         if (c.Account.Name == 'Test') {             // Take some action here         }      } }  Why doesn't this work? Why am I getting null values, or NullPointerExceptions?
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I am using the following code to play a sound file using the java sound API.      Clip clip = AudioSystem.getClip();     AudioInputStream inputStream = AudioSystem.getAudioInputStream(stream);     clip.open(inputStream);     clip.start();   The method call to the Clip.start() method returns immediately, and the system playbacks the sound file in a background thread. I want my method to pause until the playback has completed.  Is there any nice way to do it?  EDIT: For everyone interested in my final solution, based on the answer from Uri, I used the code below:  private final BlockingQueue&lt;URL&gt; queue = new ArrayBlockingQueue&lt;URL&gt;(1);  public void playSoundStream(InputStream stream) {     Clip clip = AudioSystem.getClip();     AudioInputStream inputStream = AudioSystem.getAudioInputStream(stream);     clip.open(inputStream);     clip.start();     LineListener listener = new LineListener() {         public void update(LineEvent event) {                 if (event.getType() != Type.STOP) {                     return;                 }                  try {                     queue.take();                 } catch (InterruptedException e) {                     //ignore this                 }         }     }; clip.addLineListener(listener ); }
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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.
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I'm getting this error every few days. I won't see the error for a few days then I'll get a flurry of 20 or so all with in a minute or so.  I've been very thorough going throw my code so that I'm using this basic setup for my DB access.  try {   myConnection.Open();   mySqlDataAdapter.Fill(myDataTable);   myConnection.Close(); } Catch (Exception err) {   if (myConnection.State != ConnectionState.Closed) myConnection.Close();   throw err; }   The way I understand it this should execute my queries and immediately release the connection back to the pool but if something goes wrong with the query then I catch the excpetion close my connection then throw the error up, which eventually gets trapped at the application level and logs and emails me the error.  Even using this throughout my code I'm still running across the issue. What can I do to diagnose the root cause of the issue?
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When a Java VM crashes with an EXCEPTION_ACCESS_VIOLATION and produces an hs_err_pidXXX.log file, what does that indicate? The error itself is basically a null pointer exception. Is it always caused by a bug in the JVM, or are there other causes like malfunctioning hardware or software conflicts?  Edit: there is a native component, this is an SWT application on win32.
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I'm attracted to the neatness that a single file database provides. What driver/connector library is out there to connect and use SQLite with Java.  I've discovered a wrapper library, , but are there other more prominent projects available?
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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.
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I'm trying to create an activity that presents some data to the user. The data is such that it can be divided into 'words', each being a widget, and sequence of 'words' would form the data ('sentence'?), the ViewGroup widget containing the words. As space required for all 'words' in a 'sentence' would exceed the available horizontal space on the display, I would like to wrap these 'sentences' as you would a normal piece of text.  The following code:  public class WrapTest extends Activity {     /** Called when the activity is first created. */     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         LinearLayout l = new LinearLayout(this);         LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(                 LinearLayout.LayoutParams.FILL_PARENT,                 LinearLayout.LayoutParams.WRAP_CONTENT);         LinearLayout.LayoutParams mlp = new LinearLayout.LayoutParams(                 new ViewGroup.MarginLayoutParams(                         LinearLayout.LayoutParams.WRAP_CONTENT,                         LinearLayout.LayoutParams.WRAP_CONTENT));         mlp.setMargins(0, 0, 2, 0);          for (int i = 0; i &lt; 10; i++) {             TextView t = new TextView(this);             t.setText("Hello");             t.setBackgroundColor(Color.RED);             t.setSingleLine(true);             l.addView(t, mlp);         }          setContentView(l, lp);     } }   yields something like the left picture, but I would want a layout presenting the same widgets like in the right one.        Is there such a layout or combination of layouts and parameters, or do I have to implement my own ViewGroup for this?