Is there a way I can store the value retrieved from the Firebase to be stored in a String Variable? Here is my code retrieving the Value of "rface":  ref.addListenerForSingleValueEvent(new com.google.firebase.database.ValueEventListener() {                 @Override                 public void onDataChange(com.google.firebase.database.DataSnapshot dataSnapshot) {                     rface = dataSnapshot.child("face").getValue(String.class);                 }                  @Override                 public void onCancelled(DatabaseError databaseError) {                 }             });   And I want to implement and if condition:  if (rface=="0") {     do this }   The rface contains a string value in my Firebase Database. When I try to use this If condition Android Studio says:      Operator "==" can not be applied to 'java.util.Objects','java.lang.String'
I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?
Related (but not the same):         Earlier today I asked a question about aligning equations in an enumerate environment and got an answer that seemed to work for the example I gave, but it turns out I wasn't really specific enough for my problem.  I'm using align* environments, often as the only part of a list item. (If you're wondering why I'm not using more words to introduce the align*, these are mostly homework solutions where most of the work is algebra, etc.)  Here's my code and what it makes (above the middle line):  \begin{enumerate}   \item \begin{align*}     x^2 + y^2 &amp;= x^2 + (iy)^2 \\               &amp;= (x + iy) (x - iy)   \end{align*}   \item \begin{align*}     \frac{1}{n^2-4} &amp;= \frac14 \frac{4}{(n-2)(n+2)} \\                     &amp;= \frac14 \left( \frac{1}{n-2}-\frac{1}{n+2} \right)   \end{align*} \end{enumerate}     I'm trying to make the baseline of the first line of the align* environment the same as the number's baseline—I want the first line of the align* to have the same vertical position (centered horizontally in the same way) relative to its number as in the second half of my picture. (Side question: why is there so much space before the align* starts?) Limits: How to evaluate $\lim\limits_{x\rightarrow \infty}\sqrt[n]{x^{n}+a_{n-1}x^{n-1}+\cdots+a_{0}}-x$ This is being asked in an effort to cut down on duplicates, see here: , and here: .    What methods can be used to evaluate the limit $$\lim_{x\rightarrow\infty} \sqrt[n]{x^{n}+a_{n-1}x^{n-1}+\cdots+a_{0}}-x.$$  In other words, if I am given a polynomial $P(x)=x^n + a_{n-1}x^{n-1} +\cdots +a_1 x+ a_0$, how would I find $$\lim_{x\rightarrow\infty} P(x)^{1/n}-x.$$  For example, how would I evaluate limits such as $$\lim_{x\rightarrow\infty} \sqrt{x^2 +x+1}-x$$ or $$\lim_{x\rightarrow\infty} \sqrt[5]{x^5 +x^3 +99x+101}-x.$$ Make file in linux readonly Annuity notation in LaTeX Modiagram will not compile Differentiable functions satisfying $f'(f(x))=f(f'(x))$ Can a character use the Misty Step spell to escape from the Iron Bands of Bilarro? Can a character escape the  (DMG p. 177, listed in the SRD as the ) with the  spell? To clarify, I am not asking if the bands prevent teleportation. I am asking whether the bands are teleported with the character as he teleports using misty step. How to download all OpenStreetMap highways in a large area? I need to download all highways as line features from OpenStreetMap in a large area (about 10.000km²). Therefore I wanted to use overpass-turbo with the following statement in the wizard:   highway=*   in my chosen bounding box.  Unfortunately it looks like my bounding box is too big, because I get the error:   runtime error: Query run out of memory using about 2048 MB of RAM.   Do I have to change my overpass turbo query or is it not possible to download large datasets in overpass turbo? Which alternative method could I use to download all highways as line features in a larger region. I need to have all attributes, like the type of the highway, "foot=yes/no/...", "access="yes/no/....", etc. and if I use something like geofabrik, these attributes do not appear. Low wifi signal in 14.04 LTS Android and getting a view with id cast as a string Someone flagged my question as already answered, but it's not I asked a question regarding a very specific feature of a program and whether or not it works with a larger program.  Within hours someone had marked it with "This question may already have an answer here of a similar question, but not related to my question.  The question I asked IS NOT ADDRESSED in the referred-to question. It's frustrating to spend half an hour putting together an intelligent and specific question, and then have someone mark it as a duplicate (or possible duplicate), which apparently causes people to skip over my question. I haven't received any more responses since the question was flagged.   Two questions:  (1) How do I get this flagging removed and (2) what's the best way to prevent these "helpful" flaggings in the future? How to prove: if $a,b \in \mathbb N$, then $a^{1/b}$ is an integer or an irrational number? OR operator in C not working The MathJax code in Mathematics Stack Exchange doesn't render after I updated to the new version (It used to):     App Version: 1.6.2.5 Device: iPhone 6s OS Version: Version 9.0 (Build 13A342) What does "\" mean in math In a Linear Algebra textbook I am reading, the following is stated: $b\notin \operatorname{span}(A \cup \{a\})\setminus \operatorname{span}(A)$. It does so without explaining what "$\setminus$" means. I apologize if this question does not belong here but I just want to understand what it means. I can close the question if someone just comments on its meaning. One very convenient property of $\mathbb{R}$ as a ring is that there is an upper bound for the degree of irreducible polynomials in $\mathbb{R}[x]$, as      If $f\in\mathbb{R}[x]$ has degree larger than $2$, then $f$ is reducible.   However, the proof as I know depends highly on the fact that $\mathbb{C}$ is algebraically closed, and the very nice property: $z\in\mathbb{C}$ is in $\mathbb{R}$ if and only if $z=\bar{z}$.  This makes a generalization to other integral domains rather difficult. So the problem is      For what kind of integral domain $R$, we have a finite upper bound on the degree of irreducible elements in $R[x]$?   Some most familiar examples are ruled out: in $\mathbb{Z}[x]$, $\mathbb{Q}[x]$ and $\mathbb{F}_{p}[x]$, there is not such a bound. Unfortunately these exhaust all integral domains about which I have a working knowledge.  Another result might help is , which says if we can find a prime ideal $\mathfrak{p}$ in $R$ such that $\mathfrak{p}^2\neq\mathfrak{p}$, then by picking $a\in\mathfrak{p}^2\backslash\mathfrak{p}$ we have an irreducible $a+x^d$, where $d$ can be arbitrary, and hence the upper bound is not possible.  So we only need to focus on domains where $\mathfrak{p}^2=\mathfrak{p}$ for all prime ideals. This seems to be a quite strong restriction but I am not sure what to make of it.  Can someone give a hint?  Thanks! I would like to see my review audit history What does the author mean by 'back to back' and 'hidden city' ticketing hacks? This is my first post on this forum :)  I've been trying for a while to solve this problem about symmetric difference of two sets:     Given two sets $A$ and $B$, we call symmetric difference of $A$ and $B$ the following:      $$A\mathrel{\triangle}B = (A\cup B)-(A\cap B)$$      Show that if $A\mathrel{\triangle} B = \emptyset$, then $(A\subset B) \vee (B\subset A)$.   I don’t know where to start; thank you very much for the help :) Prove that if $X$ and it's closure $\overline X$ are connected and if $X\subset Y \subset \overline X$, show that Y is also connected. Can anyone give me a proof of the statement that if $X$ and its closure $\overline X$ are connected and if $X\subset Y \subset \overline X$, show that Y is also connected?  Thank you.