I wrote a simple code to provide a mini system for a game ticket reservation and while running my project i got some errors in the following function as shown below in the code   Code:   public void reverseTicket(int seatNum,int gameCode,int categ,int price)  {     checkseat(seatNum);     for(int i=0;i&lt;=seat.counter;i++)     {     if(set[seat.counter].available==true)     {       gameCode=gameCode;      set[seat.counter].number=seatNum;      set[seat.counter].category=categ;      set[seat.counter].price=price;         seat.counter++;         break;      }     else     {         System.out.println("is seat number is full");        }       }  }     public void checkseat(int num){  for(int i=0;i&lt; set.length;i++)  {      if(set[i].number==num)      {          System.out.println("Seat is reserved");          set[i].available=false;          break;      }      }  }   the errors appeared:   Exception in thread "main" java.lang.NullPointerException at sports.game.tickt.fans.checkseat(SportsGameTickt.java:199) at sports.game.tickt.fans.reverseTicket(SportsGameTickt.java:170)   How can I fix that please?
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?
How do you open a command line? How do you access the command line or run option to put the commands into the system? series of young adult science fiction books from early 1980s about last of a race of martial experts that sees the destruction of his home planet I remember that the main character is trying to find the group that destroyed his home planet while he was on a mission. His planet was very difficult to live on and the people became expert in martial arts and were the best soldiers in the galaxy. They were mercenaries and often helped against tyrants. There was a very memorable section in at least one book about an initiation task that the main character had to do in that he had to survive in their wilderness for days. He was at some point surrounded in a old building by thousands of poisonous worm/snake creatures that he managed to survive until rescued by the leaders. Windows installer for Ubuntu 14.04 LTS onwards Is there any Windows installer (wubi) for Ubuntu 14.04 LTS?  When I mount the .iso file with Daemon Tools and run wubi.exe, it just asks me if I want to reboot (I think that's useful only when the .iso  is burned on CD), so is there no "real" installation? Will reformatting my hard drive fix bad sectors on it? Divisor function asymptotics Define $\tau_{r}(n) = \sum_{d_1...d_r = n}1$.   One exercise in a book on sieve theory asked for an elementary proof by induction of the fact that   $$\sum_{n\le x}\tau_r(n) = \frac{1}{(r - 1)!}x(\ln x)^{r - 1} + O\left(x(\ln x)^{r - 2}\right)$$  The base case $r = 2$ is easy with reversing the order of summation.  The only other progress that I made was the fact that $\sum_{n\le x}\tau_{r}(n) = \sum_{d\le x}\left\lfloor\frac{x}{d}\right\rfloor\tau_{r- 1}(d)$, but I don't know how to proceed. Find all entire functions $f(z)$ such that $|f(z)|=1$ for $|z|=1$ "not a valid identifier" when I do "export $PATH" When I run export $PATH in bash, I get the error not a valid identifier. Why? Extending from two classes Google Image Search using Android I have an image on my smartphone and I want to paste it into Google Image Search to see if I can get similar images.  I can do this by pasting the image using desktop but not using Android ...  Is there such a possibility? Clone Method not working I am trying to Clone a lead when certain condition is arrived using before trigger but i am not able to see cloned record.   for( Lead ld : Trigger.new ) {                          if(ld.Integration_Source__c == 'Hubspot' &amp;&amp; Trigger.isUpdate){         Lead LeadBeforeUpd = Trigger.oldMap.get( ld.Id );         if(ld.Program__c != LeadBeforeUpd.Program__c ){            Lead ClonedLead = new Lead();            ClonedLead = LeadBeforeUpd.clone(false, false, false, false);         }     }  } Square roots not on same height This part C\frac{1}{\sqrt{G}}\sqrt{\rho} doesn't seem to be on the same height as this part \sqrt{b}\sqrt{l} when compiled. What am I doing wrong?  \begin{flalign*} T=C\frac{1}{\sqrt{G}}\sqrt{\rho}\sqrt{b}\sqrt{l} &amp;&amp; \end{flalign*} Solutions to $a+b+c=12$, $a, b, c \in \mathbb{N}_0$ Let $a, b, c \in \mathbb{N}_0$. If $a+b+c=12$, how many solutions $(a,b,c)$ satisfy the equation?   Is the answer:      $729$ Justifying the Normal Approx to the Binomial Distribution through MGFs Would absolutely love if someone could help me with this question, in a step by step way to help those who are uninitiated to Statistics and Mathematics.   So, I am trying to "prove/justify" through MGFs how as n(the sample size) increases and goes to infinity, a standardized binomial distribution converges to the Standard Normal Distribution. So in the beginning we have $X_n $~$ Bin(n,p)$ then we standardize this $R.V.$ by subtracting the mean $E(X_n)=np$ and dividing by the $SD$ which is $np(1-p)$. After doing this, we get a new $R.V.$ with $mean=1$ and $variance=SD=1$. It is the distribution of this standardized quantity that converges to a fixed distribution, correct? Namely the Standard Normal Distribution. Let's call the standardized version of $X_n$, $Z_n$.   I think what we need to do is to find the MGF of $Z_n$ and show that this MGF becomes the Standard Normal Distribution's MGF as the sample size $(n)$ heads toward infinity. Now $Z_n$ is a function of $X_n$ which we know the MGF of which is $(1-p+pe^t)^n$.   Now I know that $Z_n$ is a linear transform and that we should be able to use this to simply the MGF but I don't understand how the course notes do it, mostly because they skip a lot of steps and it is difficult to follow. There is also a Taylor Series Expansion for the exponential that I am confused about although I do understand the concept of the series expansion.  Help would be greatly appreciated! I would love assistant in exactly how we can prove this via MGF.   Thanks so much in advance :) Git is automatically merging changes from a different branch to master Normally while searching using grep, the command I was using was this:  grep -nri "String"   whereas most of my colleagues do this:  grep -nri "String" *   What does the latter do (the * part)? Is it "legal" to CREATE and DROP #SomeTable more than once? How to display Trash and Home folder icons? What book has criminals wear a ring? I remember reading one of my father's books when I was younger.  It was about a guy who ended up getting in trouble with the law and was required to wear a ring that could not be removed and would shock the wearer any time they committed a crime (No matter how minor.)    The book was probably published in the early to mid 80s.  I thought the name of the book was 'The Ring', but I am unable to locate anything.  The cover had a car with a single wheel driving on a metal I-beam. Can I travel to the UK on different dates from those on my entry clearance? I have a "Standard Visitor Entry Clearance" for the UK and will be traveling there from Saudi Arabia.    Is it necessary to travel on the same date I provided on my application?  Will the Immigration Officer check?  Will it make problems if I travel on a different date? I was very inspired by Michio Kaku's  on the possibilities of quantum computing and also listening to Talia Gershon's  on it.   As I come from a business &amp; analytics background, what materials can I begin exploring to prepare to learn more about the field of quantum computing? Eg. what would I need to study to understand Peter Shor's algorithm,  on physics, etc.