Without any plugins:

You just need to enable highlight: (Idea v.2016, 2017 and 2018, previous versions may have same or similar settings) 

&gt;File -&gt; Settings -&gt; Editor -&gt; Inspections -&gt; Java -&gt; Serialization issues -&gt; Serializable class without &#39;serialVersionUID&#39; - set flag and click &#39;OK&#39;.
(For Macs, Settings is under IntelliJ IDEA -&gt; Preferences...)

Now, if your class implements `Serializable`, you will see highlight and alt+Enter on class name will ask you to generate `private static final long serialVersionUID`.

UPD: a faster way to find this setting - you might use hotkey `Ctrl+Shift+A` (find action), type `Serializable class without &#39;serialVersionUID&#39;` - the first is the one.

Easiest method: `Alt`+`Enter` on

    private static final long serialVersionUID = ;

IntelliJ will underline the space after the `=`. put your cursor on it and hit `alt`+`Enter` (`Option`+`Enter` on Mac). You&#39;ll get a popover that says &quot;Randomly Change serialVersionUID Initializer&quot;. Just hit enter, and it&#39;ll populate that space with a random long. 

Install [GenerateSerialVersionUID][1] plugin


  [1]: http://plugins.jetbrains.com/plugin/185-generateserialversionuid

IntelliJ IDEA Plugins / GenerateSerialVersionUID
https://plugins.jetbrains.com/plugin/?idea&amp;id=185

very nice, very easy to install. you can install that from plugins menu, select install from disk, select the jar file you unpacked in the lib folder. restart, control + ins, and it pops up to generate serial UID from menu. love it. :-)

How can I transform a big `object` to `array` with lodash?

    var obj = {
      22: {name:&quot;John&quot;, id:22, friends:[5,31,55], works:{books:[], films:[],}
      12: {name:&quot;Ivan&quot;, id:12, friends:[2,44,12], works:{books:[], films:[],}
    }

    // transform to 
    var arr = [{name:&quot;John&quot;, id:22...},{name:&quot;Ivan&quot;, id:12...}]

             



transform object to array with lodash

I am beginning to learn `swift` by following the iBook-`The Swift Programming Language` on Swift provided by Apple. The book says to create an empty dictionary one should use `[:]` same as while declaring array as `[]`:

I declared an empty array as follows :

    let emptyArr = [] // or String[]()

But on declaring empty dictionary, I get syntax error:

    let emptyDict = [:]

How do I declare an empty dictionary?



Swift: declare an empty dictionary

When I used ***Eclipse*** it had a nice feature to generate serial version UID.

But what to do in IntelliJ? 

***How to choose or generate identical serial version UID in IntelliJ?***

And what to do when you modify old class?

If you haven&#39;t specify the `id`, it is generated at runtime...

How to generate serial version UID in Intellij

When I used Eclipse it had a nice feature to generate serial version UID.
But what to do in IntelliJ?
How to choose or generate identical serial version UID in IntelliJ?
And what to do when you modify old class?
If you haven't specify the <code>id</code>, it is generated at runtime...

Is there any way to trigger the `SwipeRefreshLayout` programmatically? The animation should start and the `onRefresh` method from the `OnRefreshListener` interface should get called.

SwipeRefreshLayout trigger programmatically

I have two `java.util.Optional` instances and I want to get an `Optional` that either:

- Has the value of the first Optional, if it has a value.
- Has the value of the second Optional, if it has a value.
- Is empty of neither Optional has a value.

Is there a straight-forward way to do that, i.e. is there already some API to do that?

The following expressions will do that, but I have to mention the first optional twice:

    firstOptional.isPresent() ? firstOptional : secondOptional

This is exactly what `com.google.common.base.Optional.or()` does, but that method is not present in Java 8&#39;s API.

---

The accepted answer by _aioobe_ lists a few alternative approaches to overcome this omission of the `Optional` API right where such a value has to be computed (which answers my question). I&#39;ve now opted to add a utility function to my codebase:

	public static &lt;T&gt; Optional&lt;T&gt; or(Optional&lt;T&gt; a, Optional&lt;T&gt; b) {
		if (a.isPresent())
			return a;
		else
			return b;
	}


Get value from one Optional or another

Why does

    char ch = &#39;4&#39;;
    ch = &#39;4&#39; + 2;

 work, but

    char ch = &#39;4&#39;;
    ch = ch  + 2;
doesn&#39;t?

Why can&#39;t you add an int and a char in some cases?

While browsing the code for the Java 8 version of ForkJoinPool(which has a few interesting changes from Java 7) I ran across this construct ([here][1]):


    do {} while (!blocker.isReleasable() &amp;&amp;
                 !blocker.block());

I&#39;m struggling with why you would write it like this instead of just

    while (!blocker.isReleasable() &amp;&amp;
           !blocker.block());

Is it just a semantics/readability choice, since you could read the first construct as `do &quot;nothing&quot; while &quot;conditions&quot;`? Or is there some additional benefit I&#39;m missing?

  [1]: http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/687fd7c7986d/src/share/classes/java/util/concurrent/ForkJoinPool.java#l3207

Do &quot;nothing&quot; while &quot;condition&quot;

`Collectors.toMap` throws a `NullPointerException` if one of the values is `null`. I don&#39;t understand this behaviour, maps can contain null pointers as value without any problems. Is there a good reason why values cannot be null for `Collectors.toMap`?

Also, is there a nice Java 8 way of fixing this, or should I revert to plain old for loop?

An example of my problem:

    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;
    import java.util.stream.Collectors;
    
    
    class Answer {
    	private int id;
    
    	private Boolean answer;
    
    	Answer() {
    	}
    
    	Answer(int id, Boolean answer) {
    		this.id = id;
    		this.answer = answer;
    	}
    
    	public int getId() {
    		return id;
    	}
    
    	public void setId(int id) {
    		this.id = id;
    	}
    
    	public Boolean getAnswer() {
    		return answer;
    	}
    
    	public void setAnswer(Boolean answer) {
    		this.answer = answer;
    	}
    }
    
    public class Main {
    	public static void main(String[] args) {
    		List&lt;Answer&gt; answerList = new ArrayList&lt;&gt;();
    
    		answerList.add(new Answer(1, true));
    		answerList.add(new Answer(2, true));
    		answerList.add(new Answer(3, null));
    
    		Map&lt;Integer, Boolean&gt; answerMap =
    		answerList
    				.stream()
    				.collect(Collectors.toMap(Answer::getId, Answer::getAnswer));
    	}
    }

Stacktrace:

    Exception in thread &quot;main&quot; java.lang.NullPointerException
    	at java.util.HashMap.merge(HashMap.java:1216)
    	at java.util.stream.Collectors.lambda$toMap$168(Collectors.java:1320)
    	at java.util.stream.Collectors$$Lambda$5/1528902577.accept(Unknown Source)
    	at java.util.stream.ReduceOps$3ReducingSink.accept(ReduceOps.java:169)
    	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1359)
    	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)
    	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
    	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
    	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
    	at Main.main(Main.java:48)
    	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    	at java.lang.reflect.Method.invoke(Method.java:483)
    	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)

This problem still exists in Java 11.

NullPointerException in Collectors.toMap with null entry values

I have a problem converting `Object` instances to JSON:

    ob = Object()

    list_name = scaping_myObj(base_url, u, number_page)
    
    for ob in list_name:
       json_string = json.dumps(ob.__dict__)
       print json_string

In `list_name` I have a list of `Object` instances.

`json_string` return, for example:

    {&quot;city&quot;: &quot;rouen&quot;, &quot;name&quot;: &quot;1, 2, 3 Soleil&quot;}
    {&quot;city&quot;: &quot;rouen&quot;, &quot;name&quot;: &quot;Maman, les p&#39;tits bateaux&quot;}

But I would like just 1 JSON string with all the info in a list:

    [{&quot;city&quot;: &quot;rouen&quot;, &quot;name&quot;: &quot;1, 2, 3 Soleil&quot;}, {&quot;city&quot;: &quot;rouen&quot;, &quot;name&quot;: &quot;Maman, les p&#39;tits bateaux&quot;}]

List of objects to JSON with Python

With **django-rest-framework 3.0** and having these simple models:

    class Book(models.Model):
        title = models.CharField(max_length=50)
    
    
    class Page(models.Model):
        book = models.ForeignKey(Books, related_name=&#39;related_book&#39;)
        text = models.CharField(max_length=500)

And given this JSON request:

    {
       &quot;book_id&quot;:1,
       &quot;pages&quot;:[
          {
             &quot;page_id&quot;:2,
             &quot;text&quot;:&quot;loremipsum&quot;
          },
          {
             &quot;page_id&quot;:4,
             &quot;text&quot;:&quot;loremipsum&quot;
          }
       ]
    }

How can I write a nested serializer to process this JSON and for each `page` for the given `book` either create a new page or update if it exists.

    class RequestSerializer(serializers.Serializer):
        book_id = serializers.IntegerField()
        page = PageSerializer(many=True)
    

    class PageSerializer(serializers.ModelSerializer):
        class Meta:
            model = Page

I know that instantiating the serializer with an `instance` will update the current one but how should I use it inside the `create` method of nested serializer? 

django-rest-framework 3.0 create or update in nested serializer

I&#39;m implementing a RESTful web service where user has to send a signed verification token along with the request so that I could ensure that the request has not been tampered by a middle man. My current implementation is as follows.

Verification token is a VerifData object serialized into a String and then hashed and encrypted.

    class VerifData {
        int prop1;
        int prop2;
    }
In my service, I put data to be serialized into an instance of VerifData and then serialize it using Jackson ObjectMapper and passed along to the verification engine along with the verification token.

    VerfiData verifData = new VerifData(12345, 67890);
    ObjectMapper mapper = new ObjectMapper();
    String verifCodeGenerated = mapper.writeValueAsString(verifData);

But it seems that each time the application container is started, the order of properties being mapped into a string by ObjectMapper changes.
    
Ex: one time it would be

    {&quot;prop1&quot;:12345,&quot;prop2&quot;:67890}
and another time it would be

    {&quot;prop2&quot;:67890,&quot;prop1&quot;:12345}

So if client has serialized the VerifData instance as into the first String, there is 50% chance of it being failed even though it is correct.

Is there a way to get around this? Can I specify the order of properties to map by ObjectMapper (like in ascending order)? Or is there any other way to best implement this verification step. Both client and server implementations are developed by me. I use Java Security API for signing and verifying.

Jackson ObjectMapper - specify serialization order of object properties

How would you explain the workflow of Passport&#39;s serialize and deserialize methods to a layman.

1. Where does `user.id` go after `passport.serializeUser` has been called?&lt;br&gt;

2. We are calling `passport.deserializeUser` right after it where does it fit in the workflow?

        // used to serialize the user for the session
        passport.serializeUser(function(user, done) {
            done(null, user.id); 
           // where is this user.id going? Are we supposed to access this anywhere?
        });

        // used to deserialize the user
        passport.deserializeUser(function(id, done) {
            User.findById(id, function(err, user) {
                done(err, user);
            });
        });

I&#39;m still trying to wrap my head around it. I have a complete working app and am not running into errors of any kind.

I just wanted to understand what exactly is happening here?

Any help is appreciated.

Understanding passport serialize deserialize

Is it possible to get the current user in a model serializer? I&#39;d like to do so without having to branch away from generics, as it&#39;s an otherwise simple task that must be done.

My model:

    class Activity(models.Model):
        number = models.PositiveIntegerField(
            blank=True, null=True, help_text=&quot;Activity number. For record keeping only.&quot;)
        instructions = models.TextField()
        difficulty = models.ForeignKey(Difficulty)
        categories = models.ManyToManyField(Category)
        boosters = models.ManyToManyField(Booster)
    
        class Meta():
            verbose_name_plural = &quot;Activities&quot;

My serializer:

    class ActivitySerializer(serializers.ModelSerializer):
    	    
    	class Meta:
    		model = Activity

And my view:   

    class ActivityDetail(generics.RetrieveUpdateDestroyAPIView):

        queryset = Activity.objects.all()
        serializer_class = ActivityDetailSerializer

How can I get the model returned, with an additional field `user` such that my response looks like this:

    {
        &quot;id&quot;: 1, 
        &quot;difficulty&quot;: 1, 
        &quot;categories&quot;: [
            1
        ], 
        &quot;boosters&quot;: [
            1
        ],
        &quot;current_user&quot;: 1 //Current authenticated user here
    }

Get current user in Model Serializer

Running JDK 1.7 on Mac OS X and suddenly breakpoints on my project are not working, and they are appearing greyed out.  They were working earlier today, so not sure what I have done to cause this.  I am using Intellij 13.1.3.  Why would breakpoints stop working like this?



![Grey, non-functioning breakpoint in Intellij 13][1]




  [1]: http://i.stack.imgur.com/TdYYH.png


Intellij IDEA: Breakpoint not being hit, and is shown greyed out

I have many different versions of my app.  Each one is a separate IntelliJ project. Every time I open a new one, the list of configurations starts blank:

![enter image description here][1]

The annoying thing about this is I deploy to 1 VM and I have to copy and paste the debug configurations each time I want to test a different version.  IntelliJ makes this dialog modal per IntelliJ Instance, so I can&#39;t copy and paste the fields between Project Instances.  

I end up taking a screenshot of one configuration and copying the fields by hand into the other project.  It&#39;s a pretty primitive solution.  Is there a more convenient way to get a run configuration from one project to another?

I&#39;m using IntelliJ 13 on Windows 7.

---

https://stackoverflow.com/questions/5313946/can-i-share-settings-for-intellij-idea-across-different-projects may have the answer to this, but the question is different.  It&#39;s about window layout.  Therefore I don&#39;t consider it a duplicate.


  [1]: http://i.stack.imgur.com/d81Ev.png


How do I share IntelliJ Run/Debug configurations between projects?

I already know that question has been already asked very often and answers, but no one of the answers i found fixed my problem.

It&#39;s the error:

    Error:Gradle: Execution failed for task &#39;:ffcommunity:preDexDebug&#39;.
     com.android.ide.common.internal.LoggedErrorException: Failed to run command:
    	D:\Android SDK\sdk\build-tools\20.0.0\dx.bat --dex --output D:\Users\ReVo\Documents\IntelliJ IDEA\FFCommunity\ffcommunity\build\intermediates\pre-dexed\debug\bananaquery-2ee85432877a057e7414910b8127805535139d5d.jar D:\Users\ReVo\Documents\IntelliJ IDEA\FFCommunity\ffcommunity\libs\bananaquery.jar
    Error Code:
    	1
    Output:
    	UNEXPECTED TOP-LEVEL EXCEPTION:
    	com.android.dx.cf.iface.ParseException: bad class file magic (cafebabe) or version (0034.0000)
    		at com.android.dx.cf.direct.DirectClassFile.parse0(DirectClassFile.java:472)
    		at com.android.dx.cf.direct.DirectClassFile.parse(DirectClassFile.java:406)
    		at com.android.dx.cf.direct.DirectClassFile.parseToInterfacesIfNecessary(DirectClassFile.java:388)
    		at com.android.dx.cf.direct.DirectClassFile.getMagic(DirectClassFile.java:251)
    		at com.android.dx.command.dexer.Main.processClass(Main.java:665)
    		at com.android.dx.command.dexer.Main.processFileBytes(Main.java:634)
    		at com.android.dx.command.dexer.Main.access$600(Main.java:78)
    		at com.android.dx.command.dexer.Main$1.processFileBytes(Main.java:572)
    		at com.android.dx.cf.direct.ClassPathOpener.processArchive(ClassPathOpener.java:284)
    		at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:166)
    		at com.android.dx.cf.direct.ClassPathOpener.process(ClassPathOpener.java:144)
    		at com.android.dx.command.dexer.Main.processOne(Main.java:596)
    		at com.android.dx.command.dexer.Main.processAllFiles(Main.java:498)
    		at com.android.dx.command.dexer.Main.runMonoDex(Main.java:264)
    		at com.android.dx.command.dexer.Main.run(Main.java:230)
    		at com.android.dx.command.dexer.Main.main(Main.java:199)
    		at com.android.dx.command.Main.main(Main.java:103)
    	...while parsing com/comuf/revonline/bananaquery/BananaInsert.class
    	1 error; aborting


The error is `bad class file magic (cafebabe) or version (0034.0000)`.

I builded and execute the application without problems many times in the same day but now this fails everytime with this message.

---

Project SDK is `Android API 19 Platform` and project level is `1.7`.

CompileSDK is `19` and buildToolsVersion is `&#39;20.0.0&#39;`.

Compile options:

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_7
        targetCompatibility JavaVersion.VERSION_1_7
    }

and in `dependencies` i have:

    compile files(&#39;libs/bananaquery.jar&#39;)

---

The library is build with SDK `Android API 19 Platform` with project level `1.7`.

My `.jar` file is inside `libs/` folder.


I use IntelliJ IDEA 14 Preview, it could be the reason? With IntellIJ IDEA 13 it remains stuck at &quot;Gradle sync&quot;

*compile files could be useless since i have `compile fileTree(dir: &#39;libs&#39;, include: [&#39;*.jar&#39;])` too*

Bad class file magic or version

I have a git project at Android Studio and a remote at BitBucket and I changed it to use SSH instead of HTTPS. I can make everything work using Atlassian&#39;s SourceTree, but in Android Studio every time I try to push the project it says 

&gt;Push failed: fatal: Could not read from remote repository.

Does anyone have a clue about what could be happening? 

Android Studio - Push failed: fatal: Could not read from remote repository

In eclipse we use &lt;kbd&gt;Alt&lt;/kbd&gt; + &lt;kbd&gt;↑&lt;/kbd&gt;/&lt;kbd&gt;↓&lt;/kbd&gt; to move a line up or down.


Is there any shortcut in Android Studio to do the same?
Or any quick way to avoid copy &amp; paste?

Content Type	Original Author	Original Content on Stackoverflow
Question	catch23	View Question on Stackoverflow
Solution 1 - Java	Serhii Maksymchuk	View Answer on Stackoverflow
Solution 2 - Java	jeremysprofile	View Answer on Stackoverflow
Solution 3 - Java	Meo	View Answer on Stackoverflow
Solution 4 - Java	Patch Rhythm	View Answer on Stackoverflow

How to generate serial version UID in Intellij

Java Problem Overview

Java Solutions

Solution 1 - Java

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Solution 3 - Java

Solution 4 - Java

Swift: declare an empty dictionary

transform object to array with lodash

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