There are default implementations within [Comparator][1] you can use: `nullsFirst` or `nullsLast`:

    Comparator.comparing(YourObject::getStartDate, 
      Comparator.nullsFirst(Comparator.naturalOrder())
    )


  [1]: https://docs.oracle.com/javase/8/docs/api/java/util/Comparator.html

I have `HeroMockService` that will return mocked data and `HeroService` that will call back end service to retrieve heroes from database.

Assuming Angular2 has build environment, I&#39;m planning to inject `HeroMockService` to `AppComponent` if current build environment is `&quot;dev-mock&quot;`.  If current build environment is `&quot;dev-rest&quot;`, `HeroService` should be injected to `AppComponent` instead.

I would like to know how can I achieve this?

How to inject different service based on certain build environment in Angular2?

I&#39;m using arch linux and I&#39;ve installed Anaconda as per the instruction on the Anaconda site. When I&#39;m attempting to run `conda info --envs
` I get the following error:

&gt; bash: /home/lukasz/anaconda3/bin/conda:
&gt; /opt/anaconda1anaconda2anaconda3/bin/python: bad interpreter: No such
&gt; file or directory

I&#39;ve tried looking for the directory `/opt/anaconda1anaconda2anaconda3/bin/python:` but it simply doesn&#39;t exist. 

Furthermore, when I run python from the terminal it runs as normal with the following displayed at the top

    Python 3.5.2 |Anaconda custom (64-bit)| (default, Jul  2 2016, 17:53:06) 
    [GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux
    Type &quot;help&quot;, &quot;copyright&quot;, &quot;credits&quot; or &quot;license&quot; for more information.

for completeness my `.bashrc` file resembles:

    #
    # ~/.bashrc
    #

    # If not running interactively, don&#39;t do anything
    [[ $- != *i* ]] &amp;&amp; return

    alias ls=&#39;ls --color=auto&#39;
    PS1=&#39;[\u@\h \W]\$ &#39;

    # added by Anaconda3 4.0.0 installer
    export PATH=&quot;/home/lukasz/anaconda3/bin:$PATH&quot;

    # python startup for up keys
    export PYTHONSTARTUP=$HOME/.pythonstartup

I&#39;ve tried following [this](https://stackoverflow.com/questions/35246386/conda-command-not-found) and making the the appropriate changes but nothing, I&#39;ve also attempted to do [this](https://stackoverflow.com/questions/33946829/conda-command-not-found-path-is-in-bashrc) but there really isn&#39;t a solution posted. 

I would like to try to fix this without having to remove Anaconda and reinstalling it.

conda command will prompt error: &quot;Bad Interpreter: No such file or directory&quot;

I&#39;ve implemented a sorting on a collection using a lambda expression for the comparison. I have to check for null values, so I came up with this solution for the comparator


    (a,b)-&gt;(
    	(a.getStartDate() == null) 
    		? ( (b.getStartDate() == null) ? 0 : -1)
    		: ( (b.getStartDate() == null)?1:a.getStartDate().compareTo(b.getStartDate()) )
    );


I&#39;ve already checked some questions, like [this][1], but they all refer to pre-lambda code.

Do java lambda expressions give me the chance to avoid the two &#39;if&#39; statements? Can I perform the task in a cleaner way?


  [1]: https://stackoverflow.com/questions/2401606/comparator-with-null-values

Java 8 lambda comparator with null value check

I've implemented a sorting on a collection using a lambda expression for the comparison. I have to check for null values, so I came up with this solution for the comparator
<pre><code class="hljs language-css">(a,b)->(
	(a.getStartDate() == null) 
		? ( (b.getStartDate() == null) ? 0 : -1)
		: ( (b.getStartDate() == null)?1:a.getStartDate().compareTo(b.getStartDate()) )
);
</code></pre>
I've already checked some questions, like <a href="https://stackoverflow.com/questions/2401606/comparator-with-null-values" target="_blank" rel="noopener noreferrer">this</a>, but they all refer to pre-lambda code.
Do java lambda expressions give me the chance to avoid the two 'if' statements? Can I perform the task in a cleaner way?

I am looking at the new implementations in [**C# 7.0**][1] and I find it interesting that they have implemented local functions but I cannot imagine a scenario where a local function would be preferred over a lambda expression, and what is the difference between the two.

I do understand that lambdas are `anonymous` functions meanwhile local functions are not, but I can&#39;t figure out a real world scenario, where local function has advantages over lambda expressions 

Any example would be much appreciated. Thanks.




  [1]: https://blogs.msdn.microsoft.com/dotnet/2016/08/24/whats-new-in-csharp-7-0/

Local function vs Lambda C# 7.0

I&#39;m using a third-party library that has a function that takes functions as arguments. I&#39;m doing some conditional checks to decide whether or not to add a particular function as a parameter and in some cases I don&#39;t want to provide a function. Providing null in that cases throws an error.

I found this code which works, but I don&#39;t fully understand what&#39;s happening.

    compose(__DEV__ ? devTools() : f =&gt; f)

Is `f =&gt; f` equivalent to `() =&gt; {}` an empty anonymous function?

What exactly does the anonymous JavaScript function f =&gt; f do?

I&#39;m trying to make something like this:

     private String getStringIfObjectIsPresent(Optional&lt;Object&gt; object){
            object.ifPresent(() -&gt;{
                String result = &quot;result&quot;;
                //some logic with result and return it
                return result;
            }).orElseThrow(MyCustomException::new);
        }

This won&#39;t work, because ifPresent takes Consumer functional interface as parameter, which has void accept(T t). It cannot return any value. Is there any other way to do it ?


Java 8 optional: ifPresent return object orElseThrow exception

    function foo(x) {
       console.log(arguments)
    } //foo(1) prints [1]

but 

    var bar = x =&gt; console.log(arguments) 

gives the following error when invoked in the same way:

    Uncaught ReferenceError: arguments is not defined

Why do arrow functions not have the arguments array?

    auto foo = &quot;You&#39;re using g++!&quot;;
    auto compiler_detector = [foo](auto foo) { std::puts(foo); };
    compiler_detector(&quot;You&#39;re using clang++!&quot;);

 * **clang++ 3.6.0** and newer print out *&quot;You&#39;re using clang++!&quot;* and warn about the **capture** `foo` being unused.

 * **g++ 4.9.0** and newer print out *&quot;You&#39;re using g++!&quot;* and warn about the **parameter** `foo` being unused.


What compiler is more accurately following the C++ Standard here?

[**wandbox example**](http://melpon.org/wandbox/permlink/FFngRM4CwRdtcCBl)

Lambda capture and parameter with same name - who shadows the other? (clang vs gcc)

This was unexpected to me:


    &gt; Clock clock = Clock.systemUTC();

    &gt; Instant.now(clock).minus(3, ChronoUnit.DAYS);
    java.time.Instant res4 = 2016-10-04T00:57:20.840Z

    &gt; Instant.now(clock).minus(3, ChronoUnit.YEARS);
    java.time.temporal.UnsupportedTemporalTypeException: Unsupported unit: Years


As a workaround I have to do this:

    &gt; Instant.now(clock).atOffset(ZoneOffset.UTC).minus(3, ChronoUnit.YEARS).toInstant();
    java.time.Instant res11 = 2013-10-07T01:02:56.361Z

I am curios why Instant does not support YEARS. Did developers just give up on it?

(In my actual code I tried to subtract a `Period.ofYears(3)` but the quoted Instant methods are the ones being called in the end).

Why Instant does not support operations with ChronoUnit.YEARS?

Maybe this is very simple but I&#39;m actually a noob on Java 8 features and don&#39;t know how to accomplish this. I have this simple line that contains the following text:

&gt; &quot;Key, Name&quot;

and I want to convert that line into a String array, separating each value by the comma (,), however, I also want to trim every field before returning  the final array, so I did the following:

    Arrays.stream(line.split(&quot;,&quot;)).map(String::trim).toArray();

However, this returns an Object[] array rather than a String[] array. Upon further inspection, I can confirm that the contents are actually String instances, but the array itself is of Object elements. Let me illustrate this, this is what the debugger says of the returned object:

    Object[]:
        0 = (String) &quot;Key&quot;
        1 = (String) &quot;Name&quot;

 As far as I can tell, the problem is in the return type of the map call, but how can I make it return a String[] array?




Java stream toArray() convert to a specific type of array

I&#39;m trying to write a method to print the time difference between two **ZonedDateTime**s, regarding the difference between time zones.

I found some solutions but all of them were written to work with **LocalDateTime**.

Java 8: Calculate difference between two ZonedDateTime

With java8 we know use `ZoneId.default()` can get system default `ZoneId`, but how to get default `ZoneOffset`?

I see that a `ZoneId` has some &quot;rules&quot; and each rule has a `ZoneOffset`, is that means a `ZoneId` may have more than one `ZoneOffset`?

How to get default ZoneOffset in java8?

I am looking for method that can make stream of collection, but is null safe. If collection is null, empty stream is returned. Like this:
    
 	Utils.nullSafeStream(collection).filter(...);

I have created my own method:

    public static &lt;T&gt; Stream&lt;T&gt; nullSafeStream(Collection&lt;T&gt; collection) {
		if (collection == null) {
			return Stream.empty();
		}
		return collection.stream();
	}

But I am curious, if there is something like this in standard JDK?

Content Type	Original Author	Original Content on Stackoverflow
Question	Gabber	View Question on Stackoverflow
Solution 1 - Lambda	flo	View Answer on Stackoverflow

Java 8 lambda comparator with null value check

Lambda Problem Overview

Lambda Solutions

Solution 1 - Lambda

conda command will prompt error: "Bad Interpreter: No such file or directory"

How to inject different service based on certain build environment in Angular2?

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