I come across one scenario where swapping is not working when I am using a method to swap two collections.   public static void main(String[] args) {     Stack&lt;Integer&gt; one= new Stack&lt;&gt;();     Stack&lt;Integer&gt; two= new Stack&lt;&gt;();     one.push(1);     one.push(2);     swap(one, two);     two.forEach(System.out::println); }  //swap two stack private static void swap(Stack&lt;Integer&gt; one, Stack&lt;Integer&gt; two) {     Stack&lt;Integer&gt; temp = new Stack&lt;&gt;();     temp = one;     one = two;     two = temp;  }   But When I swap two collections using below code, it does swap two collections.  public static void main(String[] args) {     Stack&lt;Integer&gt; one= new Stack&lt;&gt;();     Stack&lt;Integer&gt; two= new Stack&lt;&gt;();     one.push(1);     one.push(2);     Stack&lt;Integer&gt; temp = new Stack&lt;&gt;();     temp = one;     one = two;     two = temp;     two.forEach(System.out::println); }   I would really appreciate the help. Let me know if you want more clarification.
I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?
Can the determinant of a matrix can be made $0$? An entry of an $n \times n$ matrix with nonzero determinant is defined as interesting if by changing this entry (and only this entry) the determinant of the matrix can be made $0$.   Is it true that each entry of every matrix with nonzero determinant is interesting? Is it true that there is an interesting entry in each row of a matrix with nonzero determinant? Does each imply the other? If not, does one imply the other? Why/why not?  This issue came up in response to a comment on an answer I posted .  Although google searching the relevant terms didn't produce anything that seemed particularly useful, I did notice  on the math stackexchange. However, I thought that this question was appropriate for this site too.  EDIT after reading the comments  Relative to the math.stackexchange answer I was after something more in depth, covering some of the issues dealt with in . Also, as I see it the math.stackexchange question shows that consistency doesn't imply asymptotically unbiasedness but doesn't explain much if anything about why. The OP there also takes for granted that asymptotic unbiasedness doesn't imply consistency, and thus the sole answerer so far doesn't address why this is. Error: j_id0:j_id1:j_id28:j_id30: Validation Error: Value is required Will my Chinese visa still be valid if I renew my passport? If so how does that work?  I have heard that you can travel with your new passport and just show the old passport with the valid visa when entering China. Has anyone done that? Recently?   I have also been told that you have to get a new visa, which seems somewhat logical but frustrating, especially when my Chinese visa is only a few months old.  My Chinese visa was issued in late Nov 2014 and I heard the rules changed between the US and China. My visa says it's good for 10 years and my US passport expires in 5. Show rigorously that the sum of integrals of $f$ and of its inverse is $bf(b)-af(a)$ Suppose $f$ is a continuous, strictly increasing function defined on a closed interval $[a,b]$ such that $f^{-1}$ is the inverse function of $f$. Prove that,   $$\int_{a}^bf(x)dx+\int_{f(a)}^{f(b)}f^{-1}(x)dx=bf(b)-af(a)$$   A high school student or a Calculus first year student will simply, possibly, apply change of variable technique, then integration by parts and he/she will arrive at the answer without giving much thought into the process. A smarter student would probably compare the integrals with areas and conclude that the equality is immediate.  However, I am an undergrad student of Analysis and I would want to solve the problem "carefully". That is, I wouldn't want to forget my definitions, and the conditions of each technique. For example, while applying change of variables technique, I cannot apply it blindly; I must be prudent enough to realize that the criterion to apply it includes continuous differentiability of a function. Simply with $f$ continuous, I cannot apply change of variables technique.  Is there any method to solve this problem rigorously? One may apply the techniques of integration (by parts, change of variables, etc.) only after proper justification.  The reason I am not adding any work of mine is simply that I could not proceed even one line since I am not given $f$ is differentiable. However, this seems to hold for non-differentiable functions also.  I would really want some help. Pictorial proofs and/or area arguments are invalid. NSDictionary with ordered keys I have an NSDictionary (stored in a plist) that I'm basically using as an associative array (strings as keys and values).  I want to use the array of keys as part of my application, but I'd like them to be in a specific order (not really an order that I can write an algorithm to sort them into).  I could always store a separate array of the keys, but that seems kind of kludgey because I'd always have to update the keys of the dictionary as well as the values of the array, and make sure they always correspond.  Currently I just use [myDictionary allKeys], but obviously this returns them in an arbitrary, non-guaranteed order.  Is there a data structure in Objective-C that I'm missing?  Does anyone have any suggestions on how to more elegantly do this? Split Java String by New Line I'm trying to split text in a JTextArea using a regex to split the String by \n However, this does not work and I also tried by \r\n|\r|n and many other combination of regexes. Code:  public void insertUpdate(DocumentEvent e) {     String split[], docStr = null;     Document textAreaDoc = (Document)e.getDocument();      try {         docStr = textAreaDoc.getText(textAreaDoc.getStartPosition().getOffset(), textAreaDoc.getEndPosition().getOffset());     } catch (BadLocationException e1) {         // TODO Auto-generated catch block         e1.printStackTrace();     }      split = docStr.split("\\n"); } Searching for words in question titles I'm trying to search for questions that have specific words in their titles using the  search feature, but it seems that it does not return any search results.  Using this feature, I tried to search for questions on Stack Overflow with , but this search query returns no results.  Is it still possible to filter the search results based on words in question titles? DateTime "null" value I've been searching a lot but couldn't find a solution. How do you deal with a DateTime that should be able to contain an uninitialized value (equivalent to null)? I have a class which might have a DateTime property value set or not. I was thinking of initializing the property holder to DateTime.MinValue, which then could easily be checked. I guess this is a quite common question, how do you do that? TV series from 70s or 80s - 1 female pilot was cloned from the other pilot's fingernail This was a tv show that aired in the US in the '70s or early '80s, possibly on Saturday mornings. Since I was a child, I'm assuming it was a kids program? It was comic science fiction and set on a spaceship. The only 3 specific details I remember are:   The crew traveled between ship levels by using open "jump tubes" that were similar to a giant vacuum tube message system, only without any "container" for the passenger. They just stepped into an alcove with a big hole in the floor and ceiling, then shot up or down. Frequently the show would use this as a source of slap-stick comedy.  The captain was male. The 2 pilots were female, and 1 had been cloned from the other's fingernail cell. They often disagreed about which one was the clone. How to calculate the number of days you can stay in Taiwan on a tourist visa? Tourist visas to Taiwan have an associated "maximum stay" of 30 days. For those visas, how are the days counted? Does the stay begin on the partial day that the traveler arrives or the first full day spent in the country? Does it end on the last full day spent in the country, or the actual day the traveler departs? I read a novel where several enemy alien species were stranded together on an interdicted planet.  They had to recycle everything and keep hidden. By "keep hidden" I mean make sure there is no evidence of their presence visible from space. They recycled everything and lived in camouflaged dwellings.  The younger generation was building a mixed culture community until the older home species showed up.  One of the alien races had a body made of rings or donuts of gases that mixed to express itself. Members of this species could be taken over and controlled by rings transferred from another member of the species.  The book may be 20 years old or more. Too many blanks between summation symbol and its associated expression Unable to correct problems, you have held broken packages I'm not a resident of USA. But I work on a cruise ship which required me to have C-1/D visa. I am leaving USA and traveling to Mexico but I will have a connecting flight somewhere in another US airport with 1-2 hours waiting for connecting flight to Mexico.   Do I need B1/B2 visa for that? Or my transit visa C-1/D will be enough as long as I am leaving USA? Sometimes I create Material Groups to be used as appendable reusable assets. Unfortunately sometimes parameters I want to control using a Group Node's slider are not available for routing to a Group Node's input socket. Some examples of these are the Color Ramp and the Mapping Node.  So here's what I want to do:    Can this be done? If so, how?  Thanks! Splitting all polygon features in a shapefile into smaller equal width polygons I have a shapefile of thousands of polygon features, that i would like to break up into smaller pieces (i.e. break a square into 8 equal pieces). I have read all over these boards for the right solution and haven't found one yet unfortunately. I've tried parcel editor but that only allows you to manually edit one feature at a time, and I've tried fishnet but that doesn't run through each individual feature it just processes across the entire extent of the shapefile. I have the full license for ArcGIS so all options are game. Ultimately I would like to be able to split this initial shapefile of features into a specified amount of equal width slots that each would be their own feature in the resulting shapefile.  Any thoughts? Use feature as module? Does anyone have experience with using a feature as a module? The usage I am talking about is strictly placing hooks inside the .module file. Can that trigger any sort of bug? How do I copy Team Fortress 2 to other computers? Need to find the recurrence equation for coloring a 1 by n chessboard