(This question may be a duplicate but I really didn't understand the other answers)  You have the following code:  String str ="football"; str.concat(" game"); System.out.println(str); // it prints football   But with this code:  String str ="football"; str = str + " game"; System.out.println(str); // it prints football game   So what's the difference and what's happening exactly?
Assuming String a and b:  a += b a = a.concat(b)   Under the hood, are they the same thing?  Here is concat decompiled as reference. I'd like to be able to decompile the + operator as well to see what that does.  public String concat(String s) {      int i = s.length();     if (i == 0) {         return this;     }     else {         char ac[] = new char[count + i];         getChars(0, count, ac, 0);         s.getChars(0, i, ac, count);         return new String(0, count + i, ac);     } }
Why my U.S. B1 Visa got refused under 214 (b)? How do I install Java, including in my browser, so websites with Java work? I met an interesting issue about C#. I have code like below.  List&lt;Func&lt;int&gt;&gt; actions = new List&lt;Func&lt;int&gt;&gt;();  int variable = 0; while (variable &lt; 5) {     actions.Add(() =&gt; variable * 2);     ++ variable; }  foreach (var act in actions) {     Console.WriteLine(act.Invoke()); }   I expect it to output 0, 2, 4, 6, 8. However, it actually outputs five 10s.  It seems that it is due to all actions referring to one captured variable. As a result, when they get invoked, they all have same output.  Is there a way to work round this limit to have each action instance have its own captured variable? GameJolt is a gaming platform/website that offers API access with features like achievements tracking for users, etc. I can use the API no problem on my tests but what I'm concerned about is the private key that is issued to my game. How do I ensure that it's protected from people that want to decompile my game? Once  they get the API private key, they will be able to do anything with it. To prove that if $n$ is odd, then $8 \mid n^2−1$, observe that as $n$ is odd either $n = 4k+1$ for some integer $k$ or $n=4k+3$ for some integer $k$. In the first case $n^2 -1=8(2k^2+k)$ and in the second case $n^2-1 = 8(2k^2 + 3k + 1)$.  Given an odd integer $a$, establish that $a^2 +(a+2)^2 +(a+4)^2 + 1$ is divisible by $12$. Solve by consideration of six cases. The only things I've found so far are a cart method (which ceased working in 1.6), a dispenser method (utilizing the decay on dropped items, but this requires occasional feeding), and a binary counter (which won't work for a single input but rather a fluctuating one).  I want to have a circuit that when I apply an input signal, the output signal doesn't change for 2 to 5 minutes.  When the input turns off, I again want a 2 to 5 minute delay.  I could accomplish this with (roughly) 240 to 600 redstone repeaters, but this is far in excess of being useful.  The only method I can think of, but would require a XOR gate (on the button-input and final output) to start and stop a clock attached to a binary counter.  While I can make room for a device of this size, I was hoping for something simpler. "Questions like this" or "questions like these" Jutifying: irrational + rational = irrational I am not sure how to show this. This is what I tried.   Proposition: If x is rational number and y is an irrational number then x+y is an irrational number.  Logically speaking this is  P=x is rational  Q= Y is irrational  R= x+y is irrational  $P\wedge Q \rightarrow R$  Explanation: What I did  $x=\frac{p}{q}$ P and Q integer  Y cannot be written as the a rational by definition  So therefore  $x+y=\frac{p}{q}+y$  Will not be a rational number as there cannot be a common denominator. This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, including more unit test resources, navigate to the  tag.  This canonical question is intended to address several classes of common questions by providing a quick summary and links to comprehensive resources:   How do I start writing my first unit test?  How do I unit test this code?  I need help writing this unit test.   Salesforce Stack Exchange looks for detailed, specific questions that the community can help you with, and can't write tests on your behalf. We feel that working with the resources below can help you get started, and we encourage you to make an attempt to write your test and return to SFSE with your specific questions when you encounter challenges you can't resolve. Will Windows 10's reset delete my Linux partitions? When should we use proximity rule in "either/or", and "neither/nor"? According to this , if at least one of the nouns involved is plural then it should take the plural form of the verb. Otherwise, it should take the singular form of the verb. But in the last part it says not all grammars agree to those rules thus proximity rule applies. However, it doesn't explain when to apply the proximity rule and when not to use the former rules. remove oldest files I`m trying to delete old files from directory and leave only 3 newest files.   cd /home/user1/test  while [ `ls -lAR | grep ^- | wc -l` &lt; 3 ] ; do      rm `ls -t1 /home/user/test | tail -1`     echo " - - - "  done   something is wrong with conditional statement. Box around single element in list Is there any way in latex to create a simple box around one item in a list?  I tried both \framebox, and \fbox, none of them worked  \begin{enumerate}[label=\Alph*),ref=\Alph*] {\color{red}\item null.}  \item lik vektdifferansen $GT - GK$. \item lik vektsummen $GT + GK$. \item lik vekten av $K$. \end{enumerate}   Works, but   \begin{enumerate}[label=\Alph*),ref=\Alph*]  {\color{red}  \fbox{ \item null.} }   \item lik vektdifferansen $GT - GK$. \item lik vektsummen $GT + GK$. \item lik vekten av $K$. \end{enumerate}   Does not. So yeah, any way to box a single entry in a list? Hide some fields in the NewForm.aspx for a custom list Is VGA port hot-pluggable? In meetings, I often see people detaching the VGA connector from one running laptop and connecting it to another, while the projector is still on. Is this 100% risk free, and OK by design of the VGA standard? If there's a risk involved in hot-plugging VGA, can it be removed by turning off or suspending either laptop, display, or both? I see this being done all the time without causing disaster, so clearly I'm not interested in answers stating &quot;we do it all the time, so it should be OK!&quot;. I want to know if there's a risk - real or in theory - that something breaks when doing this. EDIT: I did an internet search on the topic, and I never found a clear statement as to why it is safe or unsafe to hot swap VGA devices. The typical form is a forum question asking basically the same question as I did, and the following types of statements  Yes it's hot swappable! I do it all the time! It involves some kind of risk, so don't do it! You're some kind of moron if you think there's a risk, so just do it!  But no explanation as to why it safe or not... Joe Taylors answer below contains a link to a forum post and answers that basically give me the same statements as mentioned above. But again, no good explanation why. So I looked for an actual manual for a projector, and found . It states on page 3-1:  Connecting devices Computers and video devices can be connected to the projector at the same time. Check the user’s manual of the connecting device to confirm that it has the appropriate output connector. [image] Attention: As a safety precaution, disconnect all power to the projector and devices before making connections.  But again, no good explanation. I would like to know if the same Minecraft account used on a computer can be used on a different platform like the Xbox 360? I am not asking about playing on each simultaneously as each platform has been purchased - I am asking if you can cross play on multiple platforms with the same account. Basically I would like to know if all the saved stuff and settings from one platform will carry over to another. checking apt-get update lock file Methods to work around the problem of missing data in machine learning How do I create silhouettes in a studio environment? The trick to creating silhouettes in the field, as far as I know, is to use spot-metering and to expose for the background. However, this is a bit more difficult in a studio environment. What is the key to creating "artificial" silhouettes?  One solution that I'm considering is placing a bright flash directly behind the subject - would that work? I know there a lot of posts about ram but I'm still confused about it. I'm building a new system and because it was cheaper, I bought a 6GB kit from Corsair. So I'm wondering if I would be better off just using 4GB of it in a dual channel configuration or just add all 6GB (3 DIMMS) in a single channel configuration.   Thanks