in Line 7 i get nullpointerexception, how can i fix that ? any ideas?  private void updateHeights(BSTreeNode v) {   BSTreeNode u = v;    while (u != null) {     int bfc=updateNodeHeight(u);     u = u.parent;      if (bfc&lt;=-2) {        if( getHeight(u.left.left) &gt;= getHeight(u.left.right) ) { // Null Pointer Exception         u = rotateRight(u);        } else {         u=LR(u);       }     }   } }
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?
Drawing text and line-dasharray Is it possible with TileMills and CartoCSS? Do I need a transit visa for a layover in the United Arab Emirates? Intel Corporation Device [8086:0d4f] is not supported on Ubuntu 18.04.3 I am currently unable to install ubuntu server 18.04.03 LTS on the latest intel NUC10i7FNH.  Ubuntu always states both network adapters as unclaimed. The previous version (NUC8i7BEH) has the same network controller I219-V and worked like a charm.  *-network:0 UNCLAIMED      description:  Network controller      product: Intel Corporation      vendor: Intel Corporation      physical id: 14.3      ...   Without network it is not even possible to follow most suggestions how to get it enabled, because it is impossible to fetch new packages from internet.  Here are some more information as requested:  The output from: modprobe -v e1000e &amp;&amp; dmesg | grep e10   [ 3447.889394] e1000e: Intel(R) PRO/1000 Network Driver - 3.2.6-k [ 3447.889395] e1000e: Copyright(c) 1999 - 2015 Intel Corporation.   The output from: sudo lspci -knn  00:1f.6 Ethernet controller [0200]: Intel Corporation Device [8086:0d4f]     Subsystem: Intel Corporation Device [8086:2081] 01:00.0 PCI bridge [0604]: Intel Corporation JHL7540 Thunderbolt 3 Bridge [Titan Ridge 2C 2018] [8086:15e7] (rev 06)    For me this looks somehow, as the kernal driver would not be in use :-/  Here are a few more information i got from playiung around with 19.10 desktop version.  [    0.000000] Linux version 5.3.0-29-generic (buildd@lcy01-amd64-024) (gcc version 9.2.1 20191008 (Ubuntu 9.2.1-9ubuntu2)) #31-Ubuntu SMP Fri Jan 17 17:27:26 UTC 2020 (Ubuntu 5.3.0-29.31-generic 5.3.13)   output from lshw:    *-network:0        Beschreibung: Kabellose Verbindung        Produkt: Intel Corporation        Hersteller: Intel Corporation        Physische ID: 14.3        Bus-Informationen: pci@0000:00:14.3        Logischer Name: wlp0s20f3        Version: 00        Seriennummer: c8:09:a8:9c:cd:e0        Breite: 64 bits        Takt: 33MHz        Fähigkeiten: pm msi pciexpress msix bus_master cap_list ethernet physical wireless        Konfiguration: broadcast=yes driver=iwlwifi driverversion=5.3.0-29-generic firmware=48.4fa0041f.0 ip=192.168.178.109 latency=0 link=yes multicast=yes wireless=IEEE 802.11        Ressourcen: iomemory:600-5ff irq:16 memory:6023114000-6023117fff   The output from: modprobe -v e1000e &amp;&amp; dmesg | grep e10  [    2.357430] e1000e: Intel(R) PRO/1000 Network Driver - 3.2.6-k [    2.357430] e1000e: Copyright(c) 1999 - 2015 Intel Corporation. [    2.357616] e1000e 0000:00:1f.6: Interrupt Throttling Rate (ints/sec) set to dynamic conservative mode [    2.562796] e1000e 0000:00:1f.6 0000:00:1f.6 (uninitialized): registered PHC clock [    2.634139] e1000e 0000:00:1f.6 eth0: (PCI Express:2.5GT/s:Width x1) 1c:69:7a:60:44:f0 [    2.634140] e1000e 0000:00:1f.6 eth0: Intel(R) PRO/1000 Network Connection [    2.634258] e1000e 0000:00:1f.6 eth0: MAC: 13, PHY: 12, PBA No: FFFFFF-0FF [    2.634991] e1000e 0000:00:1f.6 eno1: renamed from eth0 [    5.103285] checking generic (4000000000 e10000) vs hw (4000000000 10000000) [   15.806697] e1000e: eno1 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None    output from lspci:  00:1f.6 Ethernet controller [0200]: Intel Corporation Ethernet Connection (10) I219-V [8086:0d4f]     DeviceName:  LAN     Subsystem: Intel Corporation Ethernet Connection (10) I219-V [8086:2081]     Kernel driver in use: e1000e     Kernel modules: e1000e Scale Insetted Characters to Plot I'm struggling with my lab report. I have a questionnaire which contains Likert responses (1-7) as well as questions that require only yes or no answers. I want to see if there is a correlation between higher scores on the likert scale and responses to the binary answers to the other questions.   Specifically - the likert response is about anxiety levels. The binary (yes/no) answer is about negative consequences due to alcohol use. I want to just run the one ordinal likert item with all the negative consequence responses to see if there is a relationship. Can anyone help me?     Thanks so much for the fast comments. It definitely assures me that Spearman's Rho can be used but my main problem is the fact that i am mixing binary and ordinal variables together in the one correlation matrix.  I have one ordinal variable (anxiety - 1-7 on likert scale) crossed with 13 dichotomous (0 or 1 representing yes or no) to answers ("have you ever been hospitalised due to your alcohol use?). I get statistically significant answers (&lt;.05 and &lt; .01 but the Correlation coefficients are tiny (i.e o.2) at best.   the hospitalisation is the DV an the anxiety levels the IV.   I just think i'm doing something wrong here. should i collapse the 13 binary variables in to one some how?   i can't see how SPSS will recognise the values between 1-7 when correlating with binary answers. i keep thinking it will just read that there is something in that box (ordinal) but not recognise the value (i.e 1-7) . but people keep saying that SPSS does in fact recognise this difference and account for it. Can't connect to wireless networks on a Dell Latitude D430 As stated above, I can't connect to my home wi-fi with natty but can with Windows 7. The strange thing is I that I have gotten it to connect to other password protected networks with natty, it's just mine that it dosn't like.   I am using a WPA2 pass-code with AES Encryption and all other devises work fine on my network. Laptop used is a Dell Latitude D430. Why does bash say No such file or directory when the file is on the path Fix Accessibility of the sites on the leagues (and other pull downs that share the same code path) please The  site picker seems to be ordered on-site statistics instead of alphabetically:  This makes it very hard to find Photography, Physics, and Philosophy (for example) since they are nowhere near each other in the list. I’m open to a better solution, but as it stands, this feels a little too user-hostile to assume everyone is only interested in the first 3 to 5 top visible hits in the ordered list.  Scanning pages of unorganized contents is not optimal Keyboard input should filter and not just jump around  It also breaks accessibility when someone wishes to access the list from a keyboard (or a slower input control) as opposed to a mouse and visually. How can latex and pdflatex be both symbolic links to same executable (pdftex) and not behave the same? When I run  $ latex my_doc.tex   and   $ pdflatex my_doc.tex   it works, and when I run  $ pdftex my_doc.tex   it doesn't work.  The thing is I noticed that both LaTeX and pdflatex commands are symbolic links to the same pdftex executable. That is,  $ which latex pdflatex pdftex   yields  /usr/bin/latex /usr/bin/pdflatex /usr/bin/pdftex   and   $ ls -l /usr/bin/latex /usr/bin/pdflatex /usr/bin/pdftex   yields  /usr/bin/latex -&gt; pdftex /usr/bin/pdflatex -&gt; pdftex /usr/bin/pdftex   So how is it possible that commands being symbolic links to a same executable do not behave in the same way ?  Thanks.  I have Ubuntu 12.10 with TeXLive-full 2012.20120611-4 installed. How should a physics student study mathematics? How can I do development on my Android device? I have a pretty long commute to work and own an android phone. I figure it would be nice to do some simple programming on the way. I'm not picky on which language to code on. I usually have an internet connection on the train.  I've been looking through the android market but haven't found any apps that offer a "development environment" or an editor with a compiler. Is any development ON the Android possible? Does an app for this exist? Title does not specify "On Hold" Testing the app, I noticed the title does not specify if a question is "On Hold" ... I haven't checked specifically, but would assume it doesn't specify as "Duplicate" either ... Or am I missing it somewhere? Is it not in the title but located/displayed some other way? If it is, this could be very confusing to users. If it isn't there, it's definitely confusing to users :-)  Using: Version 1.0.1.125 on iPad3 with iOS8 How to prove: if $a,b \in \mathbb N$, then $a^{1/b}$ is an integer or an irrational number? What is a good introductory book on quantum mechanics? Topology induced by seminorms and initial topology Let's say we have a family of seminorms $(\rho_\alpha)_{\alpha \in A}$ on a vector space $V$.  There are two ways to topologize $V$ using those seminorms:   We define topology $\mathcal S$ by a subbasis consisting of sets of the form $$ B_{x, \alpha, \epsilon} =\{v \in V : \rho_\alpha(v - x) &lt; \epsilon \} $$ for some $\epsilon &gt; 0, x \in V, \alpha \in A$. We define topology $\mathcal I$ as the smallest topology in which the seminorms are continuous.   I've showed that the seminorms are continuous in $\mathcal S$, and that  implies $\mathcal I \subseteq \mathcal S$. I'm having trouble with the other direction. It is clear to me that $B_{0, \alpha, \epsilon} = \rho_\alpha^{-1}  ((-\epsilon, \epsilon ))$, so it's enough to show that vector addition is continuous in respect to $\mathcal I$, but I don't know how to do that. Where can I find information about upcoming special issues in a field of study? Help with packages in java - import does not work I'm a C++ developer - not a java developer, but have to get this code working...  I have 2 public classes that will be used by another product.  I used the package directive in each of the java files.    package com.company.thing;  class MyClass ...   When I try to compile a test app that uses that I add   import com.company.thing.*;   The javac compiler fails with errors about com.company does not exist.  (even if I compile it in the same directory as the class files I just made a package of)  I am sure I am doing something bone-headed and silly.  I've read the  pages and tried to set up a directory structure like /com/company/thing  etc, but either I have totally screwed it all up or am missing something else.  EDIT thanks for the suggestions - I had tried the classpath previously.  It does not help.  I tried compiling   javac -classpath &lt;parent&gt; client.java    and the result is:  package com.company does not exist   I have the code I want to import (the two java files) in \com\company\product.  I compile those fine.  (they contain MyClass) I even made a jar file for them.  I copied the jar file up to the parent directory.  I then did (in the parent directory with the client java file)   javac -cp &lt;jarfile&gt; *.java   the result is:  cannot access MyClass bad class file: MyClass.class(:MyClass.class) class file contains wrong class: com.company.product.MyClass Please remove or make sure it appears in the correct subdirectory of the classpath.   EDIT  I got the client code to compile and run if I used the fully qualified name for MyClass and compiled it in the parent directory.  I am totally confused now.    compiled with no classpath set - just   javac *.java    in the parent directory - and it worked fine.  I can get a test app to compile, but that is not going to cut it when i have to integrate it into the production code.  Still looking for help.  EDIT:  Finally - not sure why it didn't work before - but I cleaned up all the files all over the directory structure and now it works.    Thanks I'm going down my huge backlog of unplayed Steam games and I'm thinking the best way to tackle the list is to go through the shortest games first and then concentrate on the 20+ hour ones. I'm wondering if there's a website or something else that has an estimated amount of gameplay time for games.   Is there anything like that? Minecraft Survival Mode keyboard hard remap keys?