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Java : I want to select the first row in a table , order by time ( ascending ) , then delete that row . I do n't want to use two queries since there 's a possibility that another client could select that row before it gets deleted ( there will be several machines connected at once from different networks ) .I was think... | SELECT and DELETE |
Java : Hi I have a question regarding a log4j logger.There is a part of the logger text I do n't quite follow.The line looks as followsI had a look but I ca n't seem to find this as a regular expression , it smells strongly like it could be though and I suspect that it will be replaced by the returned value of someObje... | log4j regular expression ? [ { } ] |
Java : Id like to improove continuous delivery . I am using a Tomcat 8 and maven.I use mvn tomcat : redeploy to deploy the webapp.In tomcat documentation I found this part : Deploy A New Application Archive ( WAR ) RemotelyIf installation and startup is successful , you will receive ( ... ) Otherwise , the response wil... | Optimize continuous deployment ( cancel throu chain-of-responsibility ) |
Java : I have a rather central class responsible for some Utility methods . I wanted to provide an additional overload for a method which was declared as follows : Now since I do n't really like Rawtypes , I specified the collections out into the least common denominator I can expect : So far so good , this got rid of ... | Erasing Collections generics and conflicting overloads |
Java : We currently use Beyond Compare 3.0 and I am quite pleased with it . However , it would be great if I could easily specify an exclusion for a specific one-time case . This is needed when I am doing a code review of some refactoring . For instance : Old codeNew code : In this case , I have hundreds of changes tha... | Is there a file diff tool that allows for exceptions ? |
Java : I have integrated some HTML/JS Code into my Vaadin WebApplication by creating an AbstractJavaScriptComponent . The Component almost works as intended.How do I call the passInfo ( ) method defined in the `` connector.js '' without having to manually click the Button defined in the innerHTML of the `` chessControl... | JavaScript Scope of Vaadin 's `` AbstractJavaScriptComponent '' |
Java : I am trying to use putextra ( ) and getextra ( ) but my program is crashing after implementing itGo through my code and let me know my mistakeIf I am not using getextra ( ) and putextra ( ) the code is working flawlessly This is 1st class from where I am getting the valueNow the Second class where I am trying to... | Implementing Getextra ( ) and Putextra |
Java : I 've written a streams implementation that performs four simple reductions ( + and < ) on the lines of a file.At first I performed four streams , but I decided to write my own accumulator and combiner so that I could perform all four reductions in one stream . On small data sets ( 10,000,000 lines ) this reduce... | Can Java 8 streams cause a O ( 1 ) memory reduction on unbounded data to become O ( n ) memory because of the underlying ForkJoin implementation |
Java : Since I could n't find a standard implementation of it I created this little class , but I think something simple as this should exist somewhere already : The purpose of it is to exchange a value between two threads ( main thread + EDT in my case ) . From the code using the getValue ( ) method it looks almost li... | How do you call this kind of concurrency related class ? And is there a standard implementation ? |
Java : I have a rollback exception with hibernate on my service `` duplicateContract '' The problem is , I just ca n't debug that , there is an error with the persisted object somewhere but I have no clue ( it 's not a timeout or missing @ Transactional ) . How can I get more details for this exception ? ( maybe somewh... | How to get the SQL error origin of an UnexpectedRollbackException |
Java : I found code examples in internet for reading the data from the latest version of Google Sheet as below : But I can not find any examples , to access a particular version of the Google Sheet and get a cells value in that revision.Also please let me know , if the above requirement can be completed using google sp... | How to read data from a specific version of Google Sheet ? |
Java : I´m developing an application for Liferay 6.1 EE GA3.Under the control panel , we have the section Private plugin installer where we can install / deploy new portlets . I was using the panel and the section was workng correctly.Then i tried to install a custom portlet . For some reason the installation failed an... | Liferay 6.1 - Private Plugin installer `` disapear '' or is disabled in Control panel |
Java : Sorry for really stupid question , I 'm learning a new language and taking this code : Why the output does not produce `` ] '' character ? Has it something to do with Unicode ? PostEdited : the variable E.c was not initialized for experimentation purpose . <code> public class Exercise01 { int i ; char c ; public... | First Ever Java Program Incorrect Output |
Java : I have the following code : This works fine on my computer and on my Android device . I get strings like 0product0 etc.BUT in production , on users ' Android devices , I get strings like : Does String.format ( ) not work OK when starting with a number ? <code> int color = 0 ; int number = 0 ; // ... s = String.f... | String.format fails to format numbers on some devices ? |
Java : I 'm using removeNumbers to remove all numbers in a given string with the regex '' ( ^| ) \\d+ ( $ | ( \\d+ ) + ( $ | ) | ) '' Here 's the code : Output : Is there any better way to do this ? Edit : As suggested by @ mbomb007 in his previous answer , the regex `` ( |^ ) [ \\d ] + ( | $ ) '' works as well : <code... | Regex to find numbers in a string |
Java : Just trying a hands-on the java.lang.Record . I have gone through the documentation and the JEP-359 for some understanding . So upon reading about the implicit declaration of the constructor I thought of mixing it up with an existing code generation library - Lombok ! Now what I 've ended up creating as a minima... | Java Records and Lombok annotation - IntelliJ |
Java : my Splash activity does n't change , it only changes if I change the name to another.For example : '' SplashActivity '' - Start with a ModificationIf I change the theme to another color , I need to rename the activity to : '' SplashActivityy '' or some other name than it was.If I go back to the name `` SplashAct... | Activity Theme is not changing |
Java : i just stumbled onto this comment . in the 1.5 java source.what does this comment mean ? is it a reference to a book ? a spec ? <code> public static int lowestOneBit ( int i ) { // HD , Section 2-1 return i & -i ; } | cryptic comment in jdk source : // HD , Section 2-1 |
Java : Primitives are at it again , breaking rules , I learned before . Well not technically primitive but composed of them.I learned that whenever there 's no method more specific than rest , compile time error occurs as it happens here.Now comes primitives into the picture.Expected compile time errors occurs here.Now... | Primitive vararg parameters in method overloading |
Java : Recently , I 've noticed , it is possible to have : Is there a reason for this ? <code> class Test { public enum Season { WINTER , SPRING , SUMMER , FALL } Season field = Season.WINTER.SPRING ; // why is WINTER.SPRING possible ? } | In Java , why is it possible to qualify an Enum Constant with another Enum Constant ? |
Java : Each time our new android app released , I need to update app info on our website . So I try to update the app info automatically , by read the AndroidManifest.xml in the apk when uploaded to server.I use AXMLResource and jdom2 to get the AndroidManifest.xml and parse it.But I always get , The prefix “ data ” fo... | Java parse xml with undeclared namespace |
Java : I have a simple sticker widget that allows the user to select one of the stickers upon placing the widget . My problem is that once the device is restarted , the sticker reverts to the default one . How can I ensure that the user selected sticker remains regardless of whether the device is restarted or not ? An ... | How to ensure user selected image does n't change after restart Android ? |
Java : Is there any guarantee that an object will not be garbage collected while a thread holds its monitor ? e.g.In this case concretely , is there any guarantee that b will be non-null if thread2 ( ) is called while another thread is sleeping in thread1 ( ) ? Let 's just assume the whole of thread2 ( ) is executed wh... | Does Java guarantee that currently synchronized objects are not garbage collected ? |
Java : I need to implement current formula.It is for scoring the nodes in a taxonomy . Basically , the score of a node depends on the amount of child nodes and their scores ( ( nodes ( h+1 ) ) is the amount of nodes on the next level and Cl ( concept ) is a set of children ) .In my usecase term frequencies are only def... | Mathematical formula to a recursive method |
Java : I have some code that uses the Swing/AWT printing functionality that I want to unit test . It uses the systems native print dialog , but is there any way to get the JVM to intercept that and replace it with a mock during unit testing so that I can get a copy of the image that would be printed ? My code for print... | Unit tests for printing in Java Swing |
Java : I made a Java agent which is attached to a JVM during runtime and instruments all the loaded project classes and inserts some logging statements . There are 11k classes in total . I measured the total time taken by the transform method of my ClassFileTransformer and it was 3 seconds . But the duration of the who... | How to speed up runtime Java code instrumentation ? |
Java : I have one repository in two different folders ( folder1 and folder2 ) . Within repositories has a `` oldFile '' fileIn the folder1 I do the following steps : After that , in the folder2 I do next steps : In this case I want to get a merge conflictAnd I want to see pulled files . I got the example from here.In p... | JGit get pulled files |
Java : I want to use CoreNLP in my Android project . But when I create a CoreNLP instance like this : The project links to the following .jar files : ejml-0.23.jar stanford-corenlp-3.4.1.jarstanford-corenlp-3.4.1-models.jarOn my desktop java environment with java 1.8.0_92 , this code runs correctly , but when running t... | 'Ca n't return head of null or leaf Tree ' with CoreNLP on Android |
Java : In the documentation for public Object get ( Object obj ) method in the Field class it is stated that The value is automatically wrapped in an object if it has a primitive type.and for public void set ( Object obj , Object value ) that If the underlying field is of a primitive type , an unwrapping conversion is ... | Whats the purpose of the primitive getter/setter in Field ? |
Java : So , lets say I have some game , take Pong for example . Obviously , you generally speaking do n't want to mix game-logic into graphics classes , so the class for Ball or Paddle is sepearte from the JPanel which actually draws them . Ball has the movement logic for the ball , its current location , hit detection... | Is it bad practice to use swing and awt classes for my non-graphics related classes in my programs ? |
Java : I have the following as AppCompatSpinner 's entries : Upon selecting Pick a time.. , a TimePickerDialog is opened and the user is allowed to choose a time . Here 's how : Upon selecting Pick a time.. the first time , TimePickerDialog is successfully opened and the chosen time is shown but when I choose it again ... | AppCompatSpinner 's entries not opening TimePickerDialog on selecting it second time . Please see details |
Java : I had a coding interview over the phone and was asked this question : Given a String ( for example ) : `` aksdbaalaskdhfbblajdfhacccc aoudgalsaa bblisdfhcccc '' and an expression ( for example ) : `` a+b+c- '' where : + : means the char before it is repeated 2 times - : means the char before it is repeated 4 tim... | Finding the Number of Times an Expression Occurs in a String Continuously and Non Continuously |
Java : I am designing a game engine in Java.At the core of this engine exist the two classes Asset and Attribute , where an Asset has a list of Attributes . Most Attributes need no link back up to their Attribute , meaning that Attributes can and often do appear in the lists of more than one Asset . However , there is ... | Java : Enforcing doubly linked objects |
Java : I have a question about Java generics . Say I have the following interface : An example of usage : I would also like to be able to add Something < Integer > , Something < Double > , ... to the a Manager < Number > . I would say I have to change the signature of the add-function : So far , so good . Let 's look a... | Java - generics & wildcards & interface versus implementation |
Java : What 's the sense of this class definition , what 's kind of class is that ? <code> class Node < K extends Comparable < ? super K > , V > | Class definition class name < > |
Java : I 'm currently exploring Guice capabilities and faced a strange behaviour - when I declare variable asinjection works as expected , but when I want to declare dragon2 as interface ( it implements Creature ) , i. e. I get an error No implementation for warlock.rincewind.creatures.Creature annotated with @ com.goo... | @ Provides with @ Named does n't work for supertype declared variables |
Java : Using ZeroMQ .Context and .Socket instances , I am able to push/pull messages for example below my code for a Queue like setup : My questions are : Q1 : How to implement an active / standby mode in queues ? I mean there will be 2 queues , created for one host and port , if one queue ( the active ) fails , anothe... | How to implement an active & standby queue job-processing system in JeroMQ ? |
Java : I am new to java . I had a doubt . <code> class ArrTest { public static void main ( String args [ ] ) { int i = 0 ; int [ ] a = { 3,6 } ; a [ i ] = i = 9 ; System.out.println ( i + `` `` + a [ 0 ] + `` `` + a [ 1 ] ) ; // 9 9 6 } } | Why the following code does not throw IndexOutOfBoundsException , and print out 9 9 6 ? |
Java : i was working on the basic java program and i found verry funny thing which i am sharing with you . foo ( ) gives output ( s==s1 ) = false and bar gives ( s==s1 ) = true.I want to know why this happens . <code> public class StringTest { public static void main ( String [ ] args ) { foo ( ) ; bar ( ) ; } public s... | Why do I get different results when comparing strings after using different concatenation in Java ? |
Java : I have a code where my client send an excel file to the server . The server ( SpringBoot ) needs to 'translate ' the MultiplartFile to an excel File.From then , the data needs to be inserted into a database.However , I never need to generate an excel but rather should insert the data from the spreadsheet into th... | Save uploaded excel in database |
Java : I 'm using a PostUpdateEventListener registered viaand a few other listeners in order to track changes made by Hibernate . This works perfectly , however , I see a problem there : Let 's say , for tracking some amount by id , I simply executeon every POST_COMMIT_UPDATE ( let 's ignore other operations ) . The pr... | Reliably tracking changes made by Hibernate |
Java : Is it good programming practise , when dealing with multiple classes that need the same instance of variables , to create one central one ? For example : I have a class with a set amount of variablesI have another class that needs the same variablesAnd another that needs the same variables as the firstSo I have ... | Good programming practices with centralizing variables |
Java : Suppose you start with an auto-generated methodAnd write a test for itThen 3 month from now you decide that a more appropriate name for the method would be changeKeyTo . You refactor your production code and end up with : Life is good , however , your test name remained unchangedHow do you deal with something li... | How to refactor test code together with production code ? |
Java : Our application sends strings which then shall be localized on client side . Sometimes those are whole strings , sometimes only substring , so we have to mark them . It would be the best if it only used Unicode as it would n't require any protocol changes.Example : where 10 is length in cm but it should be conve... | Which subset of Unicode symbols should I use to mark special substrings in text ? |
Java : I use two Interfaces : My problem that I want to register a Distributor in a Distributor e.g.Distributor < Object > ==register== > Distributor < String > My first thought was to change the register method to register ( Receiver < ? extends T > receiver ) . But if I want to get the Classes the receiver is intrest... | Generic Chaos Java |
Java : Here is the original link , http : //electrotek.wordpress.com/2008/08/06/singleton-in-java-the-proper-way/I am asking why we can call the function doStuff this way in Java . <code> public enum YourSingleton { INSTANCE ; public void doStuff ( String stuff ) { System.out.println ( `` Doing `` + stuff ) ; } } YourS... | Singleton – the proper way |
Java : I am implementing a Java application using the Swing GUI framework on macOS . When using the system look and feel and a screen menu bar , Swing automatically inserts a search field called Spotlight for Help into the first menu labelled `` Help '' of the menu bar of a frame : As my application is localized , the ... | How to insert Spotlight for Help into localized macOS applications in Java ? |
Java : While investigating the subtler consequences of generational garbage collectors on application performance , I have hit a quite staggering discrepancy in the performance of a very basic operation – a simple write to a heap location – with respect to whether the value written is primitive or a reference.The micro... | What can explain the huge performance penalty of writing a reference to a heap location ? |
Java : I 'm making my very own version of Java 's Stream library for fun . Here 's my class signature : Also , I wrote a basic infinite stream iterator that would generate an infinite list based on the given function : The function generate is a special case of iterate that repeats a given element forever . In the func... | Filter Function Not Lazy |
Java : I have the sample code below : and the following exception was thrown My question is why I am not able to add new string to my list ? <code> String [ ] patternArray = { `` 1 '' , '' 2 '' , '' 3 '' } ; List < String > patternCheck = Arrays.asList ( patternArray ) ; patternCheck.add ( `` 4 '' ) ; Exception in thre... | List throwing UnsupportedOperationException |
Java : There many ways to get a good security for REST ( easy ) services . I tried already . In this case only is a Basic Authentication needed . So , not based on login , RequestFilters , etc . Please focus on this example . While adding security to one RestEasy 'post ' method , I keep on getting 401 exceptions . How ... | Handling a basic/base64 security 401 exception in RestEasy and Tomcat |
Java : I added this recursive BubbleSort algorithm to my game which runs on lwjgl . I 'm trying to sort an ArrayList of `` Cloud '' objects by a float which is the speed of this cloud.For some reason sometimes I get a `` java.lang.StackOverflowError '' at the line I invoke the method in itself.Here 's the code : And he... | BubbleSort StackOverflowError |
Java : I have a static function with the following signature for a generic type Twhich should return a list of map keys with some property.Now I want to pass a generic HashMap of type Sin calling the static function within a generic class , which has the map as a member variable.I have listed a minimal code example bel... | Inferring a generic type from a generic type in Java ( compile time error ) |
Java : What is the reason of the exception message complains about duplicate key but shows the value instead ? Instead of show `` John '' as the duplicated key , it show `` 40 '' <code> List < Employee > employees = new ArrayList < > ( ) ; employees.add ( new Employee ( `` John '' , 40 ) ) ; employees.add ( new Employe... | Duplicate Key - misleading exception information ? |
Java : Apologies that is probably the worst Title I 've used but I ca n't quite think how to word it.I 'm calling a method table.getColData ( COL_1 ) which returns a genericI am calling it twice and getting two lists of strings . I want to concatenate these and have ended up with this - which works nicely I think . I c... | casting & generics to enable list concatenation in Java 8 |
Java : I am trying to develop an ObjectPool , which can be used with any Object without changing the source of neither the Pool nor the Object - but I can´t find any way to write the get ( ) -function ( `` Maincode '' getting some Object from Pool ) as there is a Type-Mismatch ( Can not convert from Object to TestObjec... | Generic ObjectPool - how to return a generic class ? |
Java : I was going through the Martin Odersky 's book Programming in Scala with it 's section on abstract modules , and his paper Scalable Component Abstractions : http : //lampwww.epfl.ch/~odersky/papers/ScalableComponent.pdfMy takeaway is that by making your modules abstract classes instead of objects ( or classic st... | Scala-style abstract modules in C # or other languages ? |
Java : In my Java 8 app , I am scanning for whitespaces in text passed in . But \s in my Regular Expression does n't capture all whitespaces . The one whitespace that I 've found that it does n't capture so far in my testing is Non-breaking Space ( Unicode 00A0 ) . This was my regular expression that was running into t... | \s does n't actually capture all whitespace characters |
Java : I come from an Actionscript3 background and this is my first time writing any Java in my life . Hashtables seem to be similar to Dictionaries in Flash , but I want to make sure I am using them correctly . I believe the Hashtable is typed to accept Strings as keys and Typefaces as objects . Is this correct ? Is t... | Is Hashtable appropriate for storing assets ? |
Java : I 'm trying to understand Generic types in Java , and in theory it looks understandable , but when I need to apply it to real code I have problem . I want to declare abstract method which will return generic type . Let 's assume that I have some empty interface called Magicable and 2 class implements it : Magica... | Difference between using wildcards and declaring generic type in abstract method in Java |
Java : I 'm trying to ingest a mp4 file and make it a timelapse . It works with the code attached below . However , the output file has frame rate of 16*originalFrameRate . Since I do n't intend to play it as a slow motion video I 'd prefer to drop those redundant frames to make the output file smaller.I was unable to ... | mp4parse timelapse frame rate |
Java : I 'm trying to solve the multithreaded bank account problem* without using locks but using multiversion concurrency control . It 's working . It 's just a bit slow . How can I speed it up ? ( * ) I have 5 users , each starting with 200 - each randomly withdrawing 100 and depositing 100 into another bank account ... | Is it possible to solve the multithreaded bank account problem fast without locks ? |
Java : I have very simple thing to do , i have list of persons like this : Result of this array should be : Adam ( true ) , John ( false ) So i need to return list of latest entries from users , in this case John first confirmed that he is attending , then he changed his mind and told that he is not attending so i 'm r... | Good way to filter list distincted by property and ordered by date |
Java : given the interfaces ( which are very large and generated out of language definitions ) : Now compiling the interface VisitorA ( containing of about 2.000 overloaded methods ) needs about 10s.Compiling the interfaces VisitorB and VisitorC needs each about 1.5 min.But when we try to compile the interface VisitorD... | Java8 slow compiling for interfaces with thousands of default methods with the same name |
Java : The following code for Integer uses object interning : It is not clear from API documentation whether this code for Boolean also uses interned object : Obviously , it may . But does it have to ? UPDATEI agree that source code can explain what actually happens ( BTW , thanks for the answers ) . To make the questi... | Is boolean interned in Java ? |
Java : I have a method to rotate images but I always receive an OutMemoryError , but my images in the gallery iare taken from camera and size width is 5000~ from phone I resized photo to width 1280 and height 960my first method for show and resize image is And my method for rotate image is where is my error ? * -- -- -... | Android image resize error memory |
Java : My IDE ( IntelliJ IDEA ) is telling me that I have the option to remove the braces on this if statement : To become : I understand how this makes sense , and it 's tempting to lose the indent , but my concern is that readability may suffer . The latter looks cleaner , but is the space saved worth the potential c... | Should multiple if statements like `` if ( condition ) if ( condition ) ... '' be avoided in Java ? |
Java : I have a BigDecimal List such as : Then , I have another List of Integers : These integers refer to the index by which I want to reorder the first list . So , I would like to reorder the first list to be : I 'm using Java 8 . <code> [ 50.0,26.2,29.3 ] [ 2,1,0 ] [ 29.3,26.2,50.0 ] | How to Order one list by the index values stored in another list |
Java : I am creating a custom class to set the max height of a NestedScrollView , based on the answer provided in this StackOverflow question : How to set the Maximum Height for a NestedScrollView in Android ? However , when I include the custom class ( MaxHeightNestedScrollView ) in my activity_main.xml code layout , ... | Android : Custom class for setting the max height of a NestedScrollView does not work ( there is no scrollbar ) |
Java : Due to a bug in the sigar library version I am using ( returns bogus values for swap ) , I tried using com.sun.management.OperatingSystemMXBean instead . This worked fine and gave me the desired results ( on Windows ) .However this breaks with java 9 . Is there another way to query swap file / partition informat... | Querying swap space in java 9 |
Java : & & is a short-circuit operator evaluated from left to right , so if the operand on the left side of & & operator is evaluated to false , evaluation should not continue . BUT I expected that the ++ should be evaluated before & & because it has higher precedence , and ( from the link ) : Operators with higher pre... | Java operator precendece confusion & & and ++ |
Java : I 'm a Java programmer . I have little knowledge on C # . But from the blogs I have read , Java supports only pass-by-value-of-reference whereas in C # the default is pass-by-value-of-reference but the programmer can use pass by reference if needed . I have penned down my understanding of how a swap function wor... | how does a swap method work in C # at a memory level ? |
Java : I 'm looking for a java api that will correctly identify if a given ip address is private or local . This code seems to work for most ipv4/ipv6 addresses : Particularly , it identifies `` fec0 : : '' as a local/private type address but it does not identify , for example , `` fc00 : : '' or `` fd00 : : '' as loca... | Is there a java api that will identify the ipv6 address fd00 : : as local/private ? |
Java : I am working on a bytecode instrumentation project . Currently when handling objects , the verifier throws an error most of the time . So I would like to get things clear concerning rules with objects ( I read the JVMS but could n't find the answer I was looking for ) : I am instrumenting the NEW instruction : o... | Bytecode and Objects |
Java : While making up some arrays I noticed that prints out but only prints the stack location . I know char and String are both very different , but how come the JVM knows to output chars for the first and only a stack location for the second ? I am using IntelliJ and the command System.out.println ( javaArray ) ; <c... | Java Array Char And String Difference In Array |
Java : It is said in manual , that if child does not implement Scrollable , then JScrollPane rely on preferredSize properties of it 's content.Apparently this is not true for me . I am increasing preferred height , but JScrollPane does not feel or react on it . <code> package tests ; import java.awt.BorderLayout ; impo... | How to implement JScrollPane child behavior ? |
Java : I am trying to deserialize the following XML : My Jackson classes are : Bar is identical , just a different class name . ( In the real code they are different , this is just an example ) .And the root class isWhen I try to deserialize the XML , using this codeThe result is this ( note the lack of `` AAA '' ) : H... | Jackson XML deserialization skips field when using multiple useWrapping = false |
Java : I need a function which can calculate the mathematical combination of ( n , k ) for a card game . My current attempt is to use a function based on usual Factorial method : It 's working very well but the matter is when I use some range of number ( n value max is 52 and k value max is 4 ) , it keeps me returning ... | Combinatory issue due to Factorial overflow |
Java : I am working on a small java bytecode instrumentation tool . The general idea is to have all of a class methods renamed with a _CONGU suffix , creating then proxy methods with the original method names that will call their _CONGU counterparts . For instance , if a class C contains a int m ( ) { return 1 ; } meth... | Wrong number of arguments in stack when trying to instrument java bytecode |
Java : I replied to a question earlier about thread safety which did not get a definite answer ( I think ) .So I have been trying to convince myself that the design is broken ( visibility ) by having thousands of threads read and write that object - but I have not been able to get anything unexpected . That is obviousl... | How can one break this ( non ? ) thread safe object ? |
Java : Taken from the official Java tutorial by Oracle , see question 2 here ( boilerplate by me ) .The answer says that studentName is not eligible for garbage collection since the array students still references it . However , the final line prints `` Peter Smith '' , so to me it seems wrong that students [ 0 ] refer... | When setting an array element to a String object , does the element reference the object ? |
Java : Using Java 8 , I get a compiler error for the following code : So essentially the compiler says `` I know you return boolean but you should n't , and if you do n't I 'm not sure what method to use '' instead of `` oh you 're returning boolean , you must mean the Predicate version of the method '' ? How does this... | Function and Predicate parameter ambiguous ? |
Java : I am trying to design a data model which can hold a very large amount of data , does anyone with experience in large volumes of data have any feedback on this , ie : Based on what I have read , the only way to get transactional integrity on inserting a Transaction and updating balance is to make it one entity gr... | Transactions over very very large entity group |
Java : I am a bit confused about this method reference syntax.counter ( ) expects a BiFunction however HighTemp : :lessThanTemp is a valid argument despite HighTemp.lessThanTemp ( ) only taking one argument.What exactly is happening in the line : if ( f.func ( vals [ i ] , v ) ) ? MCVE : <code> import java.util.functio... | Confusion about two-argument method reference |
Java : This is somewhat of a follow up on Java8 retrieving lambda setter from class.I 'm trying to get a getter method for a given fieldThis is the underlying method : This does not compile , due to a type mismatch : This however does compile : And , to my surprise , this does work using the getter which was retrieved ... | Ensuring type safety on generic lambda expression |
Java : I 'm reading the source of java.util.concurrent.ArrayBlockingQueue , and found some code I do n't understand : Notice this line : Why it does n't use this.lock directly , but assigns it to a local variable ? <code> private final ReentrantLock lock ; public boolean offer ( E e ) { if ( e == null ) throw new NullP... | Why it does n't use the instance field directly , but assigns it to a local variable ? |
Java : When calling out the function testFunc ( ) , I am not using the syntax Apples.testFunc ( ) . Yet the code runs successfully . How so ? <code> class Apples { public static void main ( String args [ ] ) { testFunc ( ) ; } public static void testFunc ( ) { System.out.println ( `` Hello world ! `` ) ; } } | How a static method call works in Java ? |
Java : I am currently evaluating implementations between Apache StopWatch and Guava 's Stopwatch and the split functionality in the former intrigued me , but I am struggling to understand what exactly it does , and what value it has.According to the documentation for StopWatch : https : //commons.apache.org/proper/comm... | What is the point of Apache Lang3 StopWatch.split ( ) ? |
Java : I have a div that is a save button that has an awesome font symbol . After clicking the div , a new CSS class disabled is added where the opacity is reduced to visually signal the clicking of the button . After the save event the disabled CSS class is removed again and the button is fully visible again . If I tr... | How to listen to CSS change in Selenium ? |
Java : I 'm having an issue with libgdx skin . When the app is paused or goes into the background and then reopens all my scene2d textures are just showing up black . I assume that the underlying textures need to be reloaded.I 'm creating my skin using the following codeMy question is if there any way that I can detect... | Libgdx reload scene2d skin after application hidden |
Java : This is homework . I do not want the solution , just a small number of links or ideas.Simply speaking what I want to do is , Simple example : doThat ( ) is a method that is known to be time consuming , which results in my program blocking until results are back . And I want to use different methods of this Objec... | Remove blocking from a method |
Java : I have a strange problem with variable initialization.There is following code : What ? ? ? Variable is initialized , what is wrong ? also when I change org.junit.Assert.assertFalse to my own local method error disappears.I am using jdk 1.7.0_51 if that matters . Class code is here <code> public void test ( ) { S... | Strange variable initialization error |
Java : I have following code : If fist string equals `` email '' I want to remove first string from the Stream . For other strings from the stream I do n't need this check.How could I acheve it ? P.S.Sure I can transform it to the list , then use old school for loop but further I need stream again . <code> Stream < Str... | Remove first ( with zero index ) element from stream conditionally |
Java : Is there any significant difference ( in performance or best practices ) between those two stream creation methods ? EDITThanks to Stack Community answers I can add some addons to question completeness for new readers : As many pointed out , .boxed ( ) IntStream method is defined as : What basically re-defines i... | Java 8 primitive stream to collection mapping methods |
Java : when I open windows cmd and type jshell , it works , but when I 'm writing something . whenever I press the BackSpace key . for example if I want to delete a letter that is wrong . jshell crashes with bellow error , i 'm using windows 10 , and C : \Program Files\Java\jdk-11.0.1 is my only path in windows System ... | Jshell crashes when i press BackSpace button in windows cmd |
Java : I have defined a function in Kotlin : I have defined a Java method with this signature : I attempt to compose them like so : When I compile I get this error : Error : ( ln , col ) java : unreported exception java.io.IOException ; must be caught or declared to be thrownHow do I define my function parameters to ac... | How do I declare a function parameter to accept functions that throw ? |
Java : I have list of students.I want to return list of objects StudentResponse classes that has the course and the list of students for the course.So I can write which gives me a map Now I have to iterate through the map again to create a list of objects of StudentResponse class which has the Course and List : Is ther... | Flatten a map after Collectors.groupingBy in java |
Java : I have a method which takes String argument . In some cases I want to pass int value to that method . For invoking that method I want to convert int into String . For that I am doing the following : One more option is : Both are correct . I do n't know which is appropriate ? Which gives better performance ? Most... | String conversions in Java |
Java : As of now I have an object that looks similar to the below . Background : The problem is with this last toJSON function . I have two different functions ( listed here as TakesADataObjOrCollectionOfDataObjs and TakesAnObjectOrCollection ) which do different things based on if the object implements JSONable or not... | Java doing different things based on generic type |
Java : I 'm seeing an extremely strange issue with Maven today : it 's trying to build classes that are not in my project , but coming from dependencies . mvn compile crashes with : There is no AppConstants.java in my project , and a search with grep -r AppConstants . gives no results . The class exists in another arti... | How is it possible that Maven builds classes that are not in my project ? |
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