I have a code like this, but I don't know why result variable have false value after execution the code  int x = 234; boolean result = (x&lt;0250);   and also why the following code doesn't work properly?  System.out.println(0250);   it prints 168 !! why?!
4461
This prints 83  System.out.println(0123)   However this prints 123  System.out.println(123)   Why does it work that way?
19697
Can any one tell the bit size of boolean in Java?
57062
Today I needed a simple algorithm for checking if a number is a power of 2.  The algorithm needs to be:   Simple Correct for any ulong value.   I came up with this simple algorithm:  private bool IsPowerOfTwo(ulong number) {     if (number == 0)         return false;      for (ulong power = 1; power &gt; 0; power = power &lt;&lt; 1)     {         // This for loop used shifting for powers of 2, meaning         // that the value will become 0 after the last shift         // (from binary 1000...0000 to 0000...0000) then, the 'for'         // loop will break out.          if (power == number)             return true;         if (power &gt; number)             return false;     }     return false; }   But then I thought, how about checking if log2 x is an exactly round number? But when I checked for 2^63+1, Math.Log returned exactly 63 because of rounding. So I checked if 2 to the power 63 is equal to the original number - and it is, because the calculation is done in doubles and not in exact numbers:  private bool IsPowerOfTwo_2(ulong number) {     double log = Math.Log(number, 2);     double pow = Math.Pow(2, Math.Round(log));     return pow == number; }   This returned true for the given wrong value: 9223372036854775809.  Is there a better algorithm?
33779
I came across some very strange behaviour when working with a Map with Decimal keys today. It seems like the Decimal type can't handle Integer assignments properly, but allows them nonetheless. I've written some example code demonstrating the problem:  Map&lt;Decimal, String&gt; m = new Map&lt;Decimal, String&gt;(); m.put(1234, 'Integer key');  m.put(1234.0, 'Decimal key'); m.put(1234.5, 'Decimal Unique key');  System.debug(m.get(1234));      // =&gt; Integer key, why was this not overwritten if 1234 == 1234.0? System.debug(m.get(1234.0));    // =&gt; Decimal key System.debug(m.get(1234.5));    // =&gt; Decimal Unique key  System.debug(m);        //Order of insertion matters, newest value does not override existing one but is not shown on map printout... for(Decimal d : m.keySet()){     System.debug(d);    //...unless you print it out yourself, because this loop shows all the keys }  //Sanity check System.debug(1234 == 1234.0); //True  //Digging deeper Decimal fake_d = 1234; Decimal real_d = 1234.0; Integer real_i = 1234; //Integer fake_i = 1234.0; //Illegal assignment, typechecking only works one way, it seems  //More sanity checks System.debug(fake_d == real_d); //True (Except when used in a Map, apparently) System.debug(fake_d == real_i); //True  System.debug(m.get(real_i)); // =&gt; Integer key System.debug(m.get(fake_d)); // =&gt; Integer key, even with fake_d explicitely declared as a Decimal type, it still pretends to be an Integer. System.debug(m.get(real_d)); // =&gt; Decimal key   I found this behaviour when I tried to fetch a value from a map using a Decimal sObject field, only to find that the keys I used to populate the Map (coming from a different Decimal field) were interpreted as Integers since they had no real decimal digits.  Maybe using Decimals as Map keys is not supported for some reason? Is it expected behaviour for 1234 and 1234.0 being distinct values in this case or is this an oversight in the Map implementation?
27078
I noticed for a while now the following syntax in some of our code:  if( NULL == var){    //... }   or  if( 0 == var){   //... }   and similar things.  Can someone please explain why did the person who wrote this choose this notation instead of the common var == 0 way)?  Is it a matter of style, or does it somehow affect performance?
58103
I was answering a question and this little inconsistency popped up.  Just wondering if anyone has come across it before, or if anyone knows why this happens.  A variable that is declared within some form of scoped element (if, for loop, etc.) shouldn't be available outside that scope.  i.e.  {     // accountNames variable is not available outside this scope     Set&lt;String&gt; accountNames = new Set&lt;String&gt; {'Test Account'}; }  system.debug(accountNames);   This debug statement fails with the message:      Variable does not exist: accountNames   However, if this is part of a query string being generated, the Database.query() call somehow has access to it.  String queryString = 'SELECT Id, Name FROM Account';  if(true) {     // accountNames variable is not available outside the `if` statement     Set&lt;String&gt; accountNames = new Set&lt;String&gt; {'Test Account'};     queryString += ' WHERE Name IN :accountNames'; }  // this debug will fail if you uncomment it // system.debug(accountNames);  // however the query somehow has access to it. // create an account called Test Account to prove it.  system.debug('queryString: ' + queryString); system.debug('queryString result: ' + database.query(queryString));   But, Salesforce is smart enough to know that it's not just some random string, so the following will fail:  // Alternatively, use a random string as the variable name, and salesforce  // is smart enough to know it's gibberish String queryString2 = 'SELECT Id, Name FROM Account';  if(true) {     queryString2 += ' WHERE Name IN :randomString'; }  try {     system.debug('queryString2 result: ' + database.query(queryString2));     system.assert(false); } catch (QueryException qe)  {     system.debug(':randomString is gibberish: ' + qe.getMessage()); }     Edit:  Interestingly, the :randomString is definitely calculated only when the query is executed.  String queryString3 = 'SELECT Id, Name FROM Account'; String queryString4 = 'SELECT Id, Name FROM Account';  if(true) {     // assign to query 3 before it has a value     queryString3 += ' WHERE Name IN :randomString';      // assign to query 4 after it has been declared     Set&lt;String&gt; randomString = new Set&lt;String&gt;{'Test Account'};     queryString4 += ' WHERE Name IN :randomString'; }  // both queries return correct results, regardless of when the variable was declared system.debug('queryString3 result: ' + database.query(queryString3)); system.debug('queryString4 result: ' + database.query(queryString4));   But it's not an open slather.  The following throws an error:  String queryString = 'SELECT Id, Name FROM Account WHERE Name = :someField'; someMethod(); system.debug('queryString result: ' + database.query(queryString));  void someMethod() {     String someField = 'Test Account';     system.debug('someField: ' + someField); }     Does anyone know why this is the case, or have an explanation why this would work?  As far as I can tell, at the time that the accountNames variable is in scope, no part of the code knows that it's anything other than a string.
81621
If I write the following class:  public class Example {        int j;       int k;        public Example(int j, int k) {            j = j;            k = k;       }        public static void main(String[] args) {            Example exm = new Example(1,2);            System.out.println(exm.j);            System.out.println(exm.k);       }  }   The program compiles, but when I run the program, the main method will print out two 0s. I know that in order to say that I want to initialize the instance variables in the constructor I have to write:  this.j = j; this.k = k;   But if I don't write it, then which variable is evaluated (or considered) in the constructor (on the left and on the write hand side of the expressions)? Is is the argument or the instance variable? Does it make a difference?  Are there other cases where the use of this is obligatory?
9683
Hey all I asked this over  =) and I got a good answer but I still have no idea whats going on. I want to know how the expression got to the answer and maybe the math behind how it was reasoned.. the steps if you would be so kind. The likelihood is I don't understand the equation.   I'm not a big maths person please be gentle :p     For all those playing along at home I'm reading Absolute Java 5th   Edition by Walter Savitch (Chapter 2 Page 66).      The Expression  double d = 12345.123456789; System.out.printf("START%12.5e END %n", d);       The Answer  START 1.23451e+04END       I understand the basic principles of this printf method's arguments   for example I know the '%' represents the start of the parameters.   '12' is the number of spacing, '.5' is the times the decimal point   will move.... I see the decimal point has moved 4 places towards the   left... can someone explain the principles of e-notation. Also how   this expression came to this answer =).      As far as e-notation go's its meant to be scientific notation;      So like 5.89e-4 would mean 0.000589 (move the decimal place if minus   left if not move the decimal place right).
35975
The variable BUILDNUMBER is set to value 230. I expect 230_ to be printed for the command echo $BUILDNUMBER_ but the output is empty as shown below.  # echo $BUILDNUMBER_  # echo $BUILDNUMBER 230
24750
I've just encountered a weird problem, I'm trying to printf an integer variable, but I forgot to specify the variable name, i.e.  printf("%d");   instead of  printf("%d", integerName);   Surprisingly the program compiles, there is output and it is not random. In fact, it happens to be the very integer I wanted to print in the first place, which happens to be m-1.  The errorneous printf statement will consistently output m-1 for as long as the program keeps running... In other words, it's behaving exactly as if the statement reads  printf("%d", m-1);   Anybody knows the reason behind this behaviour? I'm using g++ without any command line options.  #include &lt;iostream&gt; #define maxN 100 #define ON 1 #define OFF 0  using namespace std;  void clearArray(int* array, int n); int fillArray(int* array, int m, int n);  int main() {     int n = -1, i, m;     int array[maxN];     int found;      scanf("%d", &amp;n);      while(n!=0)     {         found=0;         m = 1;         while(found!=1)         {             if(m != 2 &amp;&amp; m != 3 &amp;&amp; m != 4 &amp;&amp; m != 6 &amp;&amp; m != 12)             {                 clearArray(array, n);                 if(fillArray(array, m, n) == 0)                 {                     found = 1;                 }             }             m++;         }          printf("%d\n");          scanf("%d", &amp;n);     }      return 0; }  void clearArray(int* array, int n) {     for(int i = 1; i &lt;= n; i++)         array[i] = ON; }  int fillArray(int* array, int m, int n) {     int i = 1, j, offCounter = 0, incrementCounter;      while(offCounter != n)     {         if(*(array+i)==ON)          {             *(array+i) = OFF;             offCounter++;                }         else          {             j = 0;             while((*array+i+j)==OFF)             {                 j++;             }             *(array+i+j) = OFF;             offCounter++;                    }         if(*(array+13) == OFF &amp;&amp; offCounter != n) return 1;         if(offCounter ==n) break;          incrementCounter = 0;                while(incrementCounter != m)         {             i++;             if(i &gt; n) i = 1;             if(*(array+i) == ON) incrementCounter++;          }            }      return 0; }
121
I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?
27
Consider the following code:   0.1 + 0.2 == 0.3  -&gt;  false   0.1 + 0.2         -&gt;  0.30000000000000004   Why do these inaccuracies happen?
77376
var i : integer;  i := 1234567;   Given the above, I want the string "1,234,567" as output (assuming UK locale). IntToStr just gives me "1234567". I'm sure there's a one-liner for this, but I can't find it...
71281
Is this considered bad style  $$2 = \sqrt{4} &lt; \sqrt{16} = 4?$$  It seems as though this is not strictly correct, since $2 = \sqrt{4}$ is a logical proposition which represents boolean value (true or false). A boolean value cannot be less than $\sqrt{16}$.  On the other hand, I am sure that most people will correctly interpret this as shorthand for $2 = \sqrt{4},$ $\sqrt{4} &lt; \sqrt{16},$ and $\sqrt{16} = 4$
1260
I am trying to print a simple value for $AR1_p1 but the variable $i is not evaluating. for i in 1 2 3 4 do     AR1_p1=22     AR1_p2=23     AR1_p3=24     AR1_p3=25     echo $AR1_p$i done   It's like concatenating dynamically. Any suggestions on how to fix this?.
40162
Please demonstrate how the ternary operator works with a regular if/else block. Example:  Boolean isValueBig = value &gt; 100 ? true : false;     Exact Duplicate:
6852
What is the difference between below variables assignments?   var=23 var =23 var= 23 var = 23   Is there any difference in space around the assignment operator?