I am getting a java.lang.NullPointerException error, and even though I checked mInternshipId and it is the same as I was expecting, it does not work.   This is my Firebase Content    This is my Internship Class  public class Internship {     private String internshipId;     private String internshipTitle;     private String internshipDesc;     private String internshipDate;     private String internshipImage;     private String internshipCreatorId;      public Internship() {      }      public Internship(String internshipId, String internshipTitle, String internshipDesc, String internshipDate, String internshipImage, String internshipCreatorId) {         this.internshipId = internshipId;         this.internshipTitle = internshipTitle;         this.internshipDesc = internshipDesc;         this.internshipDate = internshipDate;         this.internshipImage = internshipImage;         this.internshipCreatorId = internshipCreatorId;     }      public String getInternshipTitle() {         return internshipTitle;     }       public String getInternshipId() {         return internshipId;     }      public void setInternshipId(String internshipId) {         this.internshipId = internshipId;     }      public void setInternshipTitle(String internshipTitle) {         this.internshipTitle = internshipTitle;     }      public String getInternshipDesc() {         return internshipDesc;     }      public void setInternshipDesc(String internshipDesc) {         this.internshipDesc = internshipDesc;     }      public String getInternshipDate() {         return internshipDate;     }      public void setInternshipDate(String internshipDate) {         this.internshipDate = internshipDate;     }      public String getInternshipImage() {         return internshipImage;     }      public void setInternshipImage(String internshipImage) {         this.internshipImage = internshipImage;     }      public String getInternshipCreatorId() {         return internshipCreatorId;     }      public void setInternshipCreatorId(String internshipCreatorId) {         this.internshipCreatorId = internshipCreatorId;     } }   This is where I am using it. It shows that mInternship is not been initialized. Thank you everyone in advance for your time.  //Get The Internship ID     Intent intent = getIntent();     mInternshipId = intent.getStringExtra(INTERNSHIP_ID);      //Initialize the Database Reference     databaseReference = FirebaseDatabase.getInstance().getReference().child("Internships").child(mInternshipId);     databaseReference.addValueEventListener(new ValueEventListener() {         @Override         public void onDataChange(@NonNull DataSnapshot dataSnapshot) {              //Initialize Useful Variables             mInternship = dataSnapshot.getValue(Internship.class);             organizationId = mInternship.getInternshipCreatorId();             databaseReference = FirebaseDatabase.getInstance().getReference().child("Users").child("Organizations").child(organizationId);             databaseReference.addValueEventListener(new ValueEventListener() {                 @Override                 public void onDataChange(@NonNull DataSnapshot dataSnapshot) {                     internshipLocation = (String) dataSnapshot.child("location").getValue();                 }                  @Override                 public void onCancelled(@NonNull DatabaseError databaseError) {                 }             });         }          @Override         public void onCancelled(@NonNull DatabaseError databaseError) {         }     });
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 to approach a student with bad hygiene? I teach engineering at a community college in the US. I currently have a student with very poor hygiene. He stinks pretty badly, has obviously greasy hair, doesn’t change his clothes frequently, and I usually seat him in the back of the room (during exams and labs, when I have power over seating arrangements) so I don’t have to smell his (relatively strong) body odor.  This student has also spoken with a colleague of mine about his low self-esteem. He’s worried that he isn’t making friends, and doesn’t know if the people he hangs out with are hanging out with him because they want something from him (help with classwork) or because they are truly friends.   In my opinion, this student follows me around like a puppy, and he tries too hard to impress people (students and faculty alike). I am a young-ish female faculty member and I try to create very large boundaries, especially with my male students. As an example, he frequently finds the need to explain to me (in way too much detail) why he gets questions wrong on exams (I don’t care, and I don’t need to know, which I’ve told him several times with no success).  So, I would like to mention to this student that his hygiene is off-putting and isn’t helping him out in the friends department. However, because he already follows me around like a puppy dog, I don’t want to encourage any more interaction from him. Additionally, it frankly embarrasses me to have to bring up hygiene issues with somebody in their late teens / early twenties. How can I bring this issue up while still maintaining my boundary as a female faculty member who doesn’t want her male students following her around and asking her for advice all the time?  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They take 21 damage and their maximum HP is reduced to 5.  Are they unconscious because the 11 excess damage is less than 26 or dead because it's greater than 5? I want to run a script on all files with two specific extensions on a disk with a hierarchy of multiple nested folders.  My script works fine when I choose a folder further down the line with fewer subfolders but I'd like to run it on an entire archive with over a thousand folders.  The AppleScript takes forever to get all the files and then exits without returning anything and without executing the operations after getting the files.  No timeout message, no error message.  And the Finder becomes unresponsive (and remains stuck after the script exits).   set myFolder to choose folder with prompt "Choose a folder:"     tell application "Finder"         try             set eafFiles to (every file in entire contents of myFolder whose name ends with ".eaf") as alias list         on error             try                 set eafFiles to ((every file in entire contents of myFolder whose name ends with ".eaf") as alias) as list             on error                 set eafFiles to {}             end try         end try         try             set pfsxFiles to (every file in entire contents of myFolder whose name ends with ".pfsx") as alias list         on error             try                 set pfsxFiles to ((every file in entire contents of myFolder whose name ends with ".pfsx") as alias) as list             on error                 set pfsxFiles to {}             end try         end try         set myFiles to eafFiles &amp; pfsxFiles     end tell      repeat with CurrentFile in myFiles         set CurrentFile to CurrentFile as string          do shell script "perl /path/to/perl/script.pl " &amp; quoted form of CurrentFile     end repeat I'm looking into using Named Credentials (spring '15) to simplify apex callouts to an external web service.  I actually thought, based on the documentation, that this would help, and I'm referring correctly to the Named Credential in my code and have also given my profile access to the NC, but I'm faced with this error when I do the callout:     System.UnexpectedException: You don't have permission to view this   data. Ask your administrator to set up authentication for the external   data source   This seems to say that NC are tied to the use of External Data Source, which is absolutely unrelated to what I want to do, and the documentation doesn't mention that they are a requirement.  Have any of you run into this error when testing out Named Credentials? Is $\int_a^b f(x) dx = \int_{f(a)}^{f(b)} f^{-1}(x) dx$? I'm trying to do an incremental backup using cpio but it seems that the busybox version doesn't work the same as the normal one? This is what I've got so far:  find data/Backup -mtime -2 | cpio -cm media/USB_FLASH_2  I origianlly used:  find . -mtime -2 | cpio -cm /media/USB_FLASH_2  However, I've seen people say busybox doesn't like definitive paths while using cpio. Unsure about that though.   It returns an error that basically says I'm using cpio wrong. I can't find anyone using the busybox cpio to do things like this, does that mean i can't do it? I've looked at using rsync as well but again, it doesn't do what i would expect.  For reference I'm using PuTTY to connect through SSH to a ReadyNAS 102.  After using find . -mtime -2 | cpio -o | { cd /media/USB_FLASH_2 &amp;&amp; cpio -imd; }  i get the output:   BusyBox v1.20.2 (Debian 1:1.20.0-7) multi-call binary.  Usage: cpio [-dmvu] [-F FILE] [-H newc] [-tio] [EXTR_FILE]...  Extract or list files from a cpio archive, or create an archive using file list on stdin  Main operation mode:         -t      List         -i      Extract EXTR_FILEs (or all)         -o      Create (requires -H newc)         -d      Make leading directories         -m      Preserve mtime         -v      Verbose         -u      Overwrite         -F FILE Input (-t,-i,-p) or output (-o) file         -H newc Archive format I'm a trainee teacher and I need to pass a skills test in maths, but I'm having trouble in this particular area of algebra in finding the nth term of any sequence. I've been given a series of questions to answer one of them is:  Find the nth term of the sequence 3, 8, 15, 24.  I not only need to know the answer but more importantly the technique. This is GCSE level. I am doing exercise 3.24 of Marcus which is the following.           Let $L,K$ be number fields with $L/K$ a finite extension (of degree $[L:K] = n$) with $R = \mathcal{O}_K$ and $S = \mathcal{O}_L$. A  prime $P$ of $R$ is said to be totally ramified in $L$ iff $PS = Q^n$ for some prime $Q$ of $S$.           (a) Show that if $P$ is totally ramified in $L$ then it is totally ramified in $M$ for any intermediate field $M$, $K \subseteq M \subseteq L$.          (b) If $P$ is totally ramified in $L$ and unramified in another extension $L'$ of $K$ then $L \cap L'= K$.           (c) Give a new proof that $\Bbb{Q}(w)$ where $w = e^{2\pi i/m}$ has degree $\varphi(m)$ over $\Bbb{Q}$ (First do it for $m = p^r$ by using the fact that $(p) = (1- w)^{\varphi(m)}$ and then build up to any $m$ by using (b) above.      Now I have done (a) and (b) but when I come to (c) I fail to see how the problem is essentially circular. Even in the case $m = p^r$, I would have to use the fact that the ring of integers of $\Bbb{Q}(w)$ is $\Bbb{Z}[w]$. The proof of this fact already uses knowledge of $[\Bbb{Q}(w) : \Bbb{Q}]$ being equal to $\varphi(m)$. Am I missing something here?  Thanks. Without using sudo, preferably? Summation by parts (finite calculus) of $\sum\limits_{i=0}^{n}i\cdot a^i$ I'm studying the calculus of finite differences and have read about summation by parts:  $\sum f(x)\Delta g(x) = f(x)g(x) - \sum g(x+h)\Delta f(x)$.  The tutorials I'm using go a bit woolly at the point of introducing this technique: they use examples where they set $\Delta g(x)$ to $2^x$, and don't really show how to use it for anything a bit harder. I'm at a loss for basic examples.  I wondered if it is possible to determine  $S.n = \sum\limits_{i=0}^{n}i\cdot a^i$  using summation by parts?  If so, how is it done?  Thanks in advance. -> 683  -> 678  ???  (Doesn't really bother me too much but figured I'd report the bug...) How big an RSA key is considered secure today? I think 1024 bit RSA keys were considered secure ~5 years ago, but I assume that's not true anymore. Can 2048 or 4096 keys still be relied upon, or have we gained too much computing power in the meanwhile?  Edit: Lets assume an appropriate padding strategy. Also, I'm asking both about security of signatures and security of data encryption. Do I need to have antivirus software installed? Horizontal scroll bar occludes text I've been running into this lately.  The scroll-bar gets stuck and makes it difficult to read the text.  I'm running Chrome Version 56.0.2924.87 (64-bit) on macos. Why do the Walking Dead Zombies only show intelligence in the very first episode? I enjoy The Walking Dead, however one question keeps nagging me. The 'Walkers' are always shown to not have any intelligence or memory of having been human. This is for all seasons except the very first one.  In the very first scene of Season One, Episode One, we see a little zombie girl stop to deliberately pick up a teddy bear from the ground.   Later in the same episode we see a zombie apparently try to turn the door knob to get into Morgen Jones' house.  Also at Atlanta they can climb fences and used rocks to break glass.  After season 1 I do not recall seeing any such intelligence demonstrated by a zombie again.  My question is: are these initial displays of intelligence a discrepancy in the story, or is there a plausible explanation why the Walkers performed these actions? I was making a scene in blender and I wanted to change the texture from "Material_1" to "Material_2". It lets me change it but when I go to rendered view the part looks the same. can someone please help me By 18 years of age, I want a brand new car that's $43,668 I'm from Arizona and I will be 18 in 4 months. I make about $1,200 a month from my job. I have $600 in my bank account and I don't plan to  spend any of it until I'm  18.     I'm looking to get a brand new Jeep Wrangler Rubicon that costs about  $43,000. The down payment is 10% (about $5,000) with an APR of  4.28%. The duration is 60 months with a monthly payment of  $800.  I don't have any credit. My friend suggested that I ask my parents to put my name on one of their credit cards so that I can build some credit. I'm not sure how that works. Can someone suggest a good way of going about this so I can get this car on or around my birthday?  My mom does finance work  for a big company and she told me that I should get a cheaper car. I really want this one and I'm willing to work for it. I'm getting a second job to get more money rolling in. My mom said that the only way that this would work is if I have a down payment of $15-20k. She also said that not everyone qualifies  for a car like this one. What can get me to qualify ASAP when I turn 18? Importance of Representation Theory Representation theory is a subject I want to like (it can be fun finding the representations of a group), but it's hard for me to see it as a subject that arises naturally or why it is important. I can think of two mathematical reasons for studying it:   The character table of a group is packs a lot of information about the group and is concise. It is practically/computationally nice to have explicit matrices that model a group.   But there must certainly be deeper things that I am missing. I can understand why one would want to study group actions (the axioms for a group beg you to think of elements as operators), but why look at group actions on vector spaces? Is it because linear algebra is so easy/well-known (when compared to just modules, say)?  I am also told that representation theory is important in quantum mechanics. For example, physics should be $\mathrm{SO}(3)$ invariant and when we represent this on a Hilbert space of wave-functions, we are led to information about angular momentum. But this seems to only trivially invoke representation theory since we already start with a subgroup of $\mathrm{GL}(n)$ and then extend it to act on wave functions by $\psi(x,t) \mapsto \psi(Ax,t)$ for $A$ in $\mathrm{SO}(n)$.   claims that if our physical system has $G$ as a symmetry group, then there is a correspondence between particles and representations of $G$. I'm not sure if I understand this correspondence since it seems to be saying that if we act an element of G on a state that corresponds to some particle, then this new state also corresponds to the same particle. So a particle is an orbit of the $G$ action? Anyone know of good sources that talk about this?