This is my code for the Powers superclass:  import java.util.*;  public abstract class Powers implements Sequence {    private ArrayList&lt;Double&gt; powers;     public Powers()    {       powers = new ArrayList&lt;Double&gt;();     }     public abstract List&lt;Double&gt; firstTenTerms();    public abstract List&lt;Double&gt; firstNTerms(int n);      public void setPowers(ArrayList&lt;Double&gt; newlist)    {       powers = newlist;    }     public List&lt;Double&gt; getPowers()    {       return powers;    } }   And below is my code for PowersofTwo Subclass (well, part of it, since the code is quite long):     import java.util.*;  public class PowersOfTwo extends Powers {       public PowersOfTwo()    {       super();    }     public List&lt;Double&gt; firstTenTerms()    {       if(Powers.getPowers().size()!=0)       {          while(Powers.getPowers().size()&gt;0)          {             Powers.getPowers().remove(powers.size()-1);          }       }        for(int k=0; k&lt;10; k++)       {          Powers.getPowers().add(Math.pow(2.0,(double) k));       }       return Powers.getPowers();    } }   When I try to compile the subclass, I keep on getting this kind of error message:  PowersOfTwo.java:15: error: non-static method getPowers() cannot be referenced from a static context  Or, if I just try "powers" rather than "Powers.getPowers()", I still get this:  PowersOfTwo.java:19: error: powers has private access in Powers  The problems I had encountered in classes were usually solved by using the getters, and now I am really stumped as to what to do to try fix this error. Any help would really be appreciated!
The very common beginner mistake is when you try to use a class property "statically" without making an instance of that class. It leaves you with the mentioned error message:     You can either make the non static method static or make an instance of that class to use its properties.   Why? I am not asking for solutions. I would be grateful to know what is the reason behind it. The very core reason!  private java.util.List&lt;String&gt; someMethod(){     /* Some Code */     return someList;             }  public static void main(String[] strArgs){                // The following statement causes the error. You know why..     java.util.List&lt;String&gt; someList = someMethod();          }
What are all the correct answers to the Squirrel's questions, and what is the reward when I get them all correct? I encountered The Squirrel at "A tree."              |   |                                                                         |   |                     "   Hello, I'm The                        |             |                        Squirrel. I can                        |             |                      provide you candies,                     |             |                      and lots of things.                                    |                      I know how much you                                    |        _.-'''-,      love candies. But I                                    |      .'        `\     feel alone in this                                    |     /           /          forest.       "                         |        |    /      .--^_^                                                   |        |    |     /  C ,,\                                                           |    |    |   \  _.)                           ___                            |     \   |   /  \                   ____.----'.-'                            |      '-, \./ \)\)               .-' --  __.-'                   |            \        `-/   );/           ___/  - _.-'                        |             \_________''--'-'________.-' --    /                            |              -   --        -  -     -     __.-'                                              -    --    -     --   --  /                                                 _________________________.-'                                 He asks you some questions. What are the correct answers, and what is the reward for getting them correct? OS volume shows as type 'FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF' When exactly does combat start and surprise take effect? So say I'm going to ambush an orc. I successfully sneak up on him and I attack. The DM determines that the orc is surprised. The orc happens to get an initiative roll of 19, while I get a 10. How would this work? I can only think of two reasonable resolutions to this.   The orc, having a higher initiative, goes first. Since he's surprised, he does nothing. Then it's my turn. If the orc survives my attack, it is now his turn, and being that the orc has already gone through his round of surprise, he can now attack me or whatever, and combat proceeds as normal. I, having started the combat, go first. If the orc survives my attack, but he is surprised, so he does nothing. It is now my turn again, I attack again. If the orc survives my second attack, it is now his turn, and being that the orc has already gone through his round of surprise, he can now attack me or whatever, and combat proceeds as normal.   Which one of these is correct? neither? Does starting combat secure me a turn/action at the start of initiative order like in option 2? If option 1 is correct, could I ready an action to shoot the orc, effectively granting me a similar first attack as in option 2?  Sorry if this makes no sense. Where do I find out how a command/environment is defined? Say I want to redefine the itemize environment, or make a modified version of it. I want to know how it is currently defined. Where do I find this information? If it's some particular package command, I can just look at the .sty file for that package, but if it's something more basic, I don't know where to look...  Is there a reference manual of where all this stuff is explained? Or is there a file in the depths of my texmf tree I should poke around in? The question I'm asking is pretty much:  How do you convert PSI to Velocity?  Everywhere I look it says You can't, but can you?  And what would you need to know to do so if there is no direct way to convert?  My homework is to convert 0.14 PSI into m/s.  EDIT Sorry guys my teacher does like being tricky, no clue why. Sorry for any inconvenience this may have caused. Evolutionarily speaking, why do humans have 46 chromosomes Django - specify which model manager Django admin should use Square root of an inverse gamma distributed random variable I work on the grouped t copula and try to replicate part of the following paper: &quot;The t copula with Multiple Parameters of Degrees of Freedom: Bivariate Characteristics and Application to Risk Management&quot;, Luo &amp; Shevchenko (2010). My Question: I need the distribution of the following random variable: $$ Y = \sqrt{\frac\nu X} $$ where X is Chi square distributed with v degrees of freedom. I found out that the following random variabe Z is inverse gamma distributed with alpha = v/2 and beta = v/2, $$ Z = {\frac\nu X} $$ So, basically I am looking for the distribution of the square root of an inverse gamma distributed random variable. Do you have any ideas? Can you contract the main verb '[I] have' in a sentence? Documents required by Indian citizens wishing to travel to Nepal I'm a citizen of India and I'm travelling to Nepal by air. Is an Aadhaar Card a valid document used for travelling to Nepal by air? I have noticed for a few months that my mouse will randomly jerk across the screen. I'm super paranoid about security. But this is just silly!  Has anyone else experienced this, and found out what causes it? It happens to me every couple of days. The cursor will jump across the screen about 1000+ pixels. I thought it was my mousepad - changed it, and that's not it.  I imagine it's just a hardware issue.  This is on a PC with a Razer Naga, wired mouse. The mouse worked for about a year before I started noticing these issues. They have persisted even after a reformat / reinstall. We often get questions on bicycles.stackexchange about identifying a bicycles manufacturer, model, make, and year.  Often these questions are downvoted or closed -- usually with a comment attached to them that it's not necessary to know the exact model/make/year of a bicycle if you want to fix, repair, or ride your bike. Why should owners not care about the model/make/year of their bicycle? Especially when it comes to less expensive bikes (aka BSOs) and BMX bicycles? This is intended as a canonical question that we can point closed questions to. Also see      (generally not helpful for identifying a brand/model) Find count of all combination of numbers whose sum is x Proof of Neumann Lemma Prove that if $\|A\| &lt; 1$, then $I-A$ is invertible. Here, $\|\cdot\|$ is a matrix norm induced by a vector norm.  This lemma is referred to as Neumann Lemma.  Any ideas on how to go ahead with this?  Thanks. Are there difference between those sentences?        Alex is getting married next month.     Alex will get married next month.      Seems that the first one is expressed in present continues, and the second on in future tense. Am I correct? Possible Duplicate:          The square root of a number squared is equal to the absolute value of that number. Why is $\sqrt{x^2} = |x|$? Why not just $x$? Please give me a reason and also help me prove it. What is the maximum size of a web browser's cookie's key? What is the maximum size of a web browser's cookie's key?  I know the maximum size of a cookie is 4KB, but does the key have a limitation as well? Android app intermittently shows blank body in questions and answers (multiple sites) I'm working through Rotman (1994). It's the 2nd chapter where my curiosity lead me to a question that is not from the book. Here's the problem that inspired the question:      2.8. Imbed $S_n$ as a subgroup of $A_{n+2}$, but show, for $n\ge2$, that $S_n$ cannot be imbedded in $A_{n+1}.$    Since the alternate subgroup has the property of even parity, I thought that a little investigation of parity for the second and third symmetric groups was in order. So I constructed a table for each of them, grouped by even and odd number of disjoint products.   I'll forego writing the actual table and simply provide the answers. In symmetric groups with an even idegree, two even permutations come together under composition to produce an even permutation. Two odds also make an even. Two different parities produce odd elements.   When the symmetric group has an odd degree, e.g. $S_3$, two odds make an odd, two evens make an odd, and two different parities make an even element. Exactly the opposite results from the symmetric groups with even index.   Two questions: is this enough to prove the $A_{n+1}$ case? And can this be generalized modulo 2 e.g. $A_{2n+1}$? Round double to 3 points decimal