I am getting two type of responses from the server the first one in case of the routes is being sent to the server with the JSOn string then I get as response {"status":230,"routes":[1,9,3]} or not being sent then I get {"status":201}. Currently the app crashes if the response is {"status":201} and I am getting:     Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference   How can I prevent that? I want to do nothing if that the server response?              Gson gson = new Gson();             StopsJSON data = gson.fromJson(sb.toString(), StopsJSON.class);              routes = data.getRoutes();  @Override     protected void onPostExecute(Void result) {         // Intent with Conetxt of the Asyntask class and         Intent intent = new Intent(mContext, MainActivity.class);         intent.putIntegerArrayListExtra("stop_route", routes);         intent.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);         mContext.startActivity(intent);      }   In MainActivity:  @Override     protected void onNewIntent(Intent intent) {         // TODO Auto-generated method stub         super.onNewIntent(intent);          // getIntent() should always return the most recent         setIntent(intent);          Bundle extras = getIntent().getExtras();         if (extras != null &amp;&amp; extras.containsKey("stop_route")) {              final ArrayList&lt;Integer&gt; routeList = extras                     .getIntegerArrayList("stop_route");             int routeListSize = routeList.size();             if(routeListSize &gt; 0){       } }
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?
I've noticed in the last couple of days that there have been a few occasions when there's been a sudden surge of questions in the SO "Reopen" review queue.  Normally there's either no questions at all to reopen or at most three or four, and that's still the case, except that for the last couple of days I've gone to the review page and seen about fifty-odd questions in the queue, where just moments before there had been none.  I've gone through the reviews and the questions themselves seem reasonably legitimate (including the occasional audit), so I'm not questioning that... it just seems odd that there would be so many more than usual all of a sudden, and that they'd all appear at once.  Anyone got any insights, or should I just chalk this down as "one of those things"? Best Place to put Feature Requests? Why is my multimeter stopping device from booting when measuring current? I am using a BK Precision 2709B multimeter and attempting to measure the current of a device that runs off of a ~3.7V battery. The device boots up, initializes and then goes into its lower power state. If I use the 10A setting, my device boots up just fine but I need to measure uA or mA. When I attempt to use the mA setting, the device attempts to boot and then continuously reboots. Its not able to finish its initialization process before it cuts off. The current reading on the meter is ~30mA before the device cuts off and attempts to boot up again. The meter says 400mA max, so it doesn't seem like it is over the maximum allowed current for the mA setting. Is there anything I can do to get past the initialization so I can measure the lower power state? Syntax of Using Math Mode: Empty Lines (Beginner Question) I'm just starting to learn LaTeX. I tried typing \begin{equation*}  (math goes here)  \end{equation*}  and I got a whole bunch of errors. It seems LaTeX interpreted the empty line as the equation: when it saw nothing there, I guess it just ended math mode? It then said my other commands needed $'s so I assume that's what happened. When I typed \begin{equation*} (math goes here) \end{equation*}  everything was fine. So I'm confused. If LaTeX sees an empty line in an environment, does it just interpret this as me changing my mind, and deciding not to use the declared environment? How do I restore the Unity 7 Ctrl-Alt-Numpad combination behaviour on Gnome 3? By default, instead of doing something useful, the Ctrl-Alt-Numpad key combination in Gnome 3 shoves a window in the specified direction across the entire workspace. These shortcuts do not show in the Gnome 3 keyboard settings panel; they're just there, and they're in the way.  How can I get this behavior back in Ubuntu 17.10? How do I diagnose the source of focus problem in a camera? Probably a novice question, but how do I correctly diagnose from a photo for what reason that camera wasn't able to focus properly?  It can be any 1 of the following   Unsteady hand Lens issue Metering Re-Calibration required in camera or ...   Is there a set of unsaid protocols that needs to be followed by a photographer?  Goal is to get a sharp and crisp image prior to editing.  [PS: I own a Nikon D5200.] How does one determine ladder operators systematically? In textbooks, the ladder operators are always defined," and shown to 'raise' the state of a system, but they are never actually derived.  Does one find them simply by trial and error? Or is there a more systematic method/approach to obtain them? Stone-Weierstrass theorem with $p(1/x)$ This is what happens when I launch the terminal  There was an error creating a child process  So I have been using the Ubuntu terminal on my Raspberry Pi 4 model B 8 GB with Ubuntu for a couple moths when Ubuntu 20.10 came out for the Pi. But now I have a problem where I launch the terminal and it gives that message. I have gone for alternatives and tried to fix it but all the solutions were outdated or they were on a different distro. Also the Ubuntu commands did not fix the issue because it only triggers upon a certain command. Why does the 'b' in absorb change to a 'p' in absorption? Can I still use a usb flash drive after spilling water on it? So a few months ago I accidentally spilled a little water on a few of my usb flash drives. I really want to test and see if they work, but before I do, I just want to make sure that there's no risk of damaging my computer. I'm pretty sure it's fine, but I just got a new laptop and would hate to ruin it over something stupid. Do I have to do any configuration to start brace expansion? When I run mkdir {1..10}, it just creates a dir naming {1..10}. Is it ethical to use a recommendation letter from a deceased professor? She was a really nice professor and she wrote me a good recommendation letter that resulted in a lot of good results with applications. Recently, this professor died from brain cancer, which was a fast and shocking death for me.  Tomorrow is the deadline for a grant. What should I do? Is it professional to use letters from the deceased? Generic constraints, where T : struct and where T : class Is there a clever way to show that  $$|x| - |y| \leq |x-y|$$  I believe I can think of a way to solve this using cases, but the book I'm working out of said that "A very short proof is possible if you write things in the right way" which has motivated me to figure out this quick way, but I've failed thus far and any help would be appreciated Problem writing aux file I want to show for $x\in\mathbb{R}$, the following inequality holds. $$ \left|\sin x\right|+\left|\sin (x+1)\right|+\left|\sin (x+2)\right|&gt;8/5. $$ This trigonometric inequality has been verified by Mathematica using the Plot commend. However, using the sum formula for the sine function seems doesn't work, and I cannot give a rigorous proof of it. Any suggestion, idea, or comment is welcome, thanks! How do I change the command that a launcher item launches? Execute PowerShell Script from C# with Commandline Arguments I need to execute a PowerShell script from within C#. The script needs commandline arguments.  This is what I have done so far:  RunspaceConfiguration runspaceConfiguration = RunspaceConfiguration.Create();  Runspace runspace = RunspaceFactory.CreateRunspace(runspaceConfiguration); runspace.Open();  RunspaceInvoke scriptInvoker = new RunspaceInvoke(runspace);  Pipeline pipeline = runspace.CreatePipeline(); pipeline.Commands.Add(scriptFile);  // Execute PowerShell script results = pipeline.Invoke();   scriptFile contains something like "C:\Program Files\MyProgram\Whatever.ps1".   The script uses a commandline argument such as "-key Value" whereas Value can be something like a path that also might contain spaces.  I don't get this to work. Does anyone know how to pass commandline arguments to a PowerShell script from within C# and make sure that spaces are no problem? If $[\cdot]$ denotes greatest integer function, then what is the value of natural number $n$ satisfying the equation $$[\log_21]+[\log_22]+[\log_23]+\dots[\log_2n]=1538 ?$$   My try:  Note that  $$0+1\times2+2\times2^2+3\times2^3+4\times2^4+5\times2^5+6\times2^6+7\times2^7=1538$$  But the answer is $$n=\sum_{i=0}^72^i=255.$$  How is it derived?