1) I am unable to read the elements from the list Column Wise because the size of the Column is variable.  2)I have 10 Database and have stored each of these 10 database information in a list.Each list in the database can have variable length.  having variable data.  I am able to insert the elements in the list. But I am not able to read the elements from the list Column Wise but the rows are fixed.  For Example:Let's say the elements can be any.  1 2 3  1 2 3 4 5  1 2  1 2 4   I need the output as 1,1,1,1,2,2,2,2,3,3,4,4,5     Can anyone guide me How can I get?   MyUnderstanding  I tried the following approach and Coded like this  I  MyCode:      int ar[][] = new int[10][]; //Created a 2Dimensional Array     //The Size of the row is fixed but not for Columns(as it is variable)      ArrayList&lt;Object&gt; al = new ArrayList&lt;Object&gt;();       ArrayList&lt;&lt;Object&gt; al1 = new ArrayList&lt;Object&gt;();      ArrayList&lt;Object&gt; al4 = new ArrayList&lt;Object&gt;();      for (int j = 0; j &lt; ar.length; j++) //This loop is for generating each database         {         System.out.println("Enter the Size of the list" + j);         String s1 = sc.next();         int i = Integer.parseInt(s1);         for (int k = 0; k &lt; i; k++)  //This loop is for generating the elements size inside each database {             System.out.println("Enter the Elements of the list" + j);             String s2 = sc.next();             al1.add(s2); //I store these elements in a list             ar[i] = new int[al1.size()];             al.add(al1);    //Finally store a list in a SeperateList          }      }        System.out.println("Reading each elements of the ArrayList");   MAIN PROBLEM      ListIterator ltr = al.listIterator(); // Used ListIterator to extract                                             // each                                             // List from the 10 list.      for (int i = 0; i &lt; 10; i++)      {         for (int l = 0; l &lt; ar[i].length; l++)          {             while (ltr.hasNext()) // A list AL having 10 Databases.             {                 ArrayList a0to9 = (ArrayList) ltr.next();// I have taken 1 listfrom the 10 Databases.                 ListIterator ltr1 = a0to9.listIterator(); // Used ListIterator to extract each Element from the List.                  while (ltr1.hasNext()) // If the first List contains the elements (the elements are stored in the form of list)                 {                     ArrayList elements = (ArrayList) ltr1.next(); // If the list has elements we can extract that Object                     al4.add(elements); //And store the elements in another list                     break;                 }              }         }     }      But I am getting the folloing Output   Output:  Exception in thread "main" java.lang.NullPointerException at LockWaitTimeoutTest.main(LockTest.java:48)      Can anyone guide me how can I solve this problem.   Thankx in Advance :)
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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?
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When i create new User Account and login with that credentials, it gives me this problem if admin doesnt have set thier values yet !!!**  AllotmentList = [select id, Days_Remaining__c from PTO_Allotment__c where Year__c =:year and Employee__c=:EmployeeList[0].id LIMIT 100]; //access only Current user Allotment details                 //to handle Listoutof Bound Exception wrote if-else          if(AllotmentList.size()&gt;0)         {         requests.PTO_Allotment__c=AllotmentList[0].id;         requests.Days_Remaining__c=AllotmentList[0].Days_Remaining__c;         }         else         {             //write a code when AllotmentList is empty ....         }
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I've been told that code such as:  for (int i = 0; i &lt; x.length(); i++) {     // blah }   is actually O(n^2) because of the repeated calls to x.length(). Instead I should use:  int l = x.length(); for (int i = 0; i &lt; l; i++) {     // blah }   Is this true? Is string length stored as a private integer attribute of the String class? Or does String.length() really walk the whole string just to determine its length?
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I am creating a hosted app in SharePoint. I want to retreive all the custom list from SharePoint and then from the custom lists I want to fetch column values. I got 2 columns with the names title and link. Link is a hyperlink column containing urls. My question is some of my custom lists doesnt have the column name "link" and some has. But I want to retreive those list that has that column. And title column is in every custom list. Some of the list has the column name "link" but with no values.  Error message: 0x800a138f - Runtime errors in JavaScript: Unable to retrieve the property get_url for a reference that is undefined or null      function onSuccessItemFetch() {     // Now you can access the array of SP.ListItemCollection     for (var i = 0, length = listItemsCollection.length; i &lt; length; i++) {         var items = listItemsCollection[i];         var enumerator = items.getEnumerator();          while (enumerator.moveNext()) {             var listItem = enumerator.get_current();             if (typeof listItem.get_item('Link') != "undefined" &amp;&amp; typeof listItem.get_item('Link') != null) {             itemString += listItem.get_item('Title') + "&amp;nbsp" + "&amp;nbsp" + "&amp;nbsp" + "&amp;nbsp" + "&amp;nbsp" + "&amp;nbsp" + "&lt;a href='" + listItem.get_item('Link').get_url() + "'&gt;" + "öppna formulär" + "&lt;/a&gt;" + "&lt;/br&gt;";  //oListItem.get_item('Datum')             $('#divAllaListItems').html(itemString);             }         }     } }   It works fine when I want to retrieve all the custom list titles and the title column values.
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Conditions: do not modify the original lists; JDK only, no external libraries. Bonus points for a one-liner or a JDK 1.3 version. Is there a simpler way than: List&lt;String&gt; newList = new ArrayList&lt;String&gt;(); newList.addAll(listOne); newList.addAll(listTwo);
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A weird bug was occurring in production which I was asked to look into. The issue was tracked down to a couple of variables being declared within a For loop and not being initialized on each iteration. An assumption had been made that due to the scope of their declaration they would be &quot;reset&quot; on each iteration. Could someone explain why they would not be)? (My first question, really looking forward to the responses.) The example below is obviously not the code in question but reflects the scenario:  Please excuse the code example, it looks fine in the editor preview?? for (int i =0; i&lt; 10; i++) {     decimal? testDecimal;     string testString;      switch( i % 2  )     {         case 0:         testDecimal = i / ( decimal ).32;         testString = i.ToString();             break;         default:             testDecimal = null;             testString = null;             break;     }      Console.WriteLine( &quot;Loop {0}: testDecimal={1} - testString={2}&quot;, i, testDecimal , testString ); }   EDIT: Sorry, had to rush out for child care issue. The issue was that the prod code had was that the switch statement was huge and in some &quot;case&quot;'s a check on a class' property was being made, like if (myObject.Prop != null) then testString = myObject.Stringval... At the end of the switch, (outside) a check on testString == null was being made but it was holding the value from the last iteration,hence not being null as the coder assumed with the variable being declared within the loop. Sorry if my question and example was a bit off, I got the phone call about the day care as I was banging it together. I should have mentioned I compared IL from both variables in and out the loop. So, is the common opinion that &quot;obviously the variables would not be reinitialized on each loop&quot;? A little more info, the variables WHERE being initialized on each iteration until someone got over enthusiastic with ReSharper pointing out &quot;the value is never used&quot; and removed them.  EDIT: Folks, I thank you all. As my first post I see how much clearer I should be in the future. The cause of our unexpected variable assignment can me placed on an inexperienced developer doing everything ReSharper told him and not running any unit tests after he ran a &quot;Code Cleanup&quot; on an entire solution. Looking at the history of this module in VSS I see variables Where declared outside of the loop and where initialized on each iteration. The person in question wanted his ReSharper to show &quot;all green&quot; so &quot;moved his variables closer to assignment&quot; then &quot;Removed redundant assignment&quot;! I don't think he will be doing it again...now to spend the weekend running all the unit tests he missed! How to do mark a question as answered?
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It seems that a List object cannot be stored in a List variable in C#, and can't even be explicitly cast that way.  List&lt;string&gt; sl = new List&lt;string&gt;(); List&lt;object&gt; ol; ol = sl;   results in Cannot implicitly convert type System.Collections.Generic.List&lt;string&gt; to System.Collections.Generic.List&lt;object&gt;  And then...  List&lt;string&gt; sl = new List&lt;string&gt;(); List&lt;object&gt; ol; ol = (List&lt;object&gt;)sl;   results in Cannot convert type System.Collections.Generic.List&lt;string&gt; to System.Collections.Generic.List&lt;object&gt;  Of course, you can do it by pulling everything out of the string list and putting it back in one at a time, but it is a rather convoluted solution.
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I have a list of integers, List&lt;Integer&gt; and I'd like to convert all the integer objects into Strings, thus finishing up with a new List&lt;String&gt;.  Naturally, I could create a new List&lt;String&gt; and loop through the list calling String.valueOf() for each integer, but I was wondering if there was a better (read: more automatic) way of doing it?
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Lets say I have this array,  int[] numbers = {1, 3, 4, 9, 2};   How can I delete an element by "name"? , lets say number 4?  Even ArrayList didn't help to delete?  string strNumbers = " 1, 3, 4, 9, 2"; ArrayList numbers = new ArrayList(strNumbers.Split(new char[] { ',' })); numbers.RemoveAt(numbers.IndexOf(4)); foreach (var n in numbers) {     Response.Write(n); }
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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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.NET offers a generic list container whose performance is almost identical (see Performance of Arrays vs. Lists question). However they are quite different in initialization.   Arrays are very easy to initialize with a default value, and by definition they already have certain size:  string[] Ar = new string[10];   Which allows one to safely assign random items, say:  Ar[5]="hello";   with list things are more tricky. I can see two ways of doing the same initialization, neither of which is what you would call elegant:  List&lt;string&gt; L = new List&lt;string&gt;(10); for (int i=0;i&lt;10;i++) L.Add(null);   or  string[] Ar = new string[10]; List&lt;string&gt; L = new List&lt;string&gt;(Ar);   What would be a cleaner way?  EDIT: The answers so far refer to capacity, which is something else than pre-populating a list. For example, on a list just created with a capacity of 10, one cannot do L[2]="somevalue"  EDIT 2: People wonder why I want to use lists this way, as it is not the way they are intended to be used. I can see two reasons:   One could quite convincingly argue that lists are the "next generation" arrays, adding flexibility with almost no penalty. Therefore one should use them by default. I'm pointing out they might not be as easy to initialize. What I'm currently writing is a base class offering default functionality as part of a bigger framework. In the default functionality I offer, the size of the List is known in advanced and therefore I could have used an array. However, I want to offer any base class the chance to dynamically extend it and therefore I opt for a list.
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What is the difference between using  on the array element as opposed to using ?   For example:  myArray = ['a', 'b', 'c', 'd'];  delete myArray[1]; //  or myArray.splice (1, 1);   Why even have the splice method if I can delete array elements like I can with objects?
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If you are creating a 1d array, you can implement it as a List, or else use the 'array' module in the standard library.  I have always used Lists for 1d arrays.  What is the reason or circumstance where I would want to use the array module instead?  Is it for performance and memory optimization, or am I missing something obvious?
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I've got a multidimensional associative array which includes an elements like  $data["status"] $data["response"]["url"] $data["entry"]["0"]["text"]   I've got a strings like:  $string = 'data["status"]'; $string = 'data["response"]["url"]'; $string = 'data["entry"]["0"]["text"]';   How can I convert the strings into a variable to access the proper array element? This method will need to work across any array at any of the dimensions.
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I have a file (called "number.txt") which I want to read to an array in Java. How exactly do I go ahead and do this? It is a straight-forward "1-dimensional" file, containing 100 numbers.  The problem is that I get an exception every time. Apparently it can't find it (I am sure its spelled correctly). When looking through code examples, it doesn't specify the file's entire file path, only the name of the file itself. How would I go about doing that if its necessary?  Also, when reading the file, will the array automatically contain all the lines of the file, or will I have to make a loop which which copies every line to corresponding subscript i?  I've heard of BufferedReader class, what it's purpose, and how does it corelate to reading input?
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I've been lately trying to learn more and generally test Java's serialization for both work and personal projects and I must say that the more I know about it, the less I like it. This may be caused by misinformation though so that's why I'm asking these two things from you all:  1: On byte level, how does serialization know how to match serialized values with some class?  One of my problems right here is that I made a small test with ArrayList containing values "one", "two", "three". After serialization the byte array took 78 bytes which seems awfully lot for such low amount of information(19+3+3+4 bytes). Granted there's bound to be some overhead but this leads to my second question:  2: Can serialization be considered a good method for persisting objects at all? Now obviously if I'd use some homemade XML format the persistence data would be something like this  &lt;object&gt;     &lt;class="java.util.ArrayList"&gt;     &lt;!-- Object array inside Arraylist is called elementData --&gt;     &lt;field name="elementData"&gt;         &lt;value&gt;One&lt;/value&gt;         &lt;value&gt;Two&lt;/value&gt;         &lt;value&gt;Three&lt;/value&gt;     &lt;/field&gt; &lt;/object&gt;   which, like XML in general, is a bit bloated and takes 138 bytes(without whitespaces, that is). The same in JSON could be   {     "java.util.ArrayList": {         "elementData": [             "one",             "two",             "three"         ]     } }   which is 75 bytes so already slightly  smaller than Java's serialization. With these text-based formats it's of course obvious that there has to be a way to represent your basic data as text, numbers or any combination of both.  So to recap, how does serialization work on byte/bit level, when it should be used and when it shouldn't be used and what are real benefits of serialization besides that it comes standard in Java?
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I have a python list, say l  l = [1,5,8]   I want to write a sql query to get the data for all the elements of the list, say  select name from students where id = |IN THE LIST l|   How do I accomplish this?