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Java : Here is from HashMap：I wonder why not use member variable values directly ? Why create the local variable named vs ? How is that better than : <code> transient Collection < V > values ; public Collection < V > values ( ) { Collection < V > vs = values ; if ( vs == null ) { vs = new Values ( ) ; values = vs ; } r... | Why not use values variable directly , the vs variable is not necessary |
Java : Please , tell me difference between the next situations : There is no compilation error in this caseANDThere is compilation error <code> public class Test { private static < T extends Throwable > void doThrow ( Throwable ex ) throws T { throw ( T ) ex ; } public static void main ( String [ ] args ) { doThrow ( n... | What 's the difference between the next situations |
Java : I have the below classWill the iterator ( ) call in the printElement method throw ConcurrentModificationException ? The basic question is if the lock on class object is acquired ( as done in printElement method ) , will it lock the class members/ variables too ? please help me with the answer . <code> public cla... | Does a lock on class , locks class variables too ? - java |
Java : I have a code like this : Why when creating A with no generic type getFiled returns String but getFileds returns List < Object > ? I have to define A as A < String > a = new A < > ( ) for this to work properly.Thanks , <code> public class A < T extends String > { T field ; List < T > fields ; public T getField (... | Why is the base type not returned when no generic type specified ? |
Java : Currently i have code like below . A list embedded with in another list , and i want to get the total count of the embedded list objects.I want to write a quick oneliner for this . Is there an efficient Lambda or FP trick i can do in Java 8 ? <code> int totalNo = 0 ; for ( ClassB classB : listOfClassB ) { totalN... | Accumulate count of list 's within another list |
Java : Suppose I have a simple list : The target is `` test '' and I want to add the value before the target into a new list , so the output would be [ result1 , result2 ] .It 's easy enough to add the `` test '' values with something like listTwo = listOne.stream ( ) .filter ( i - > i.equals ( `` test '' ) ) .collect ... | Find value n steps away from target in List with stream |
Java : I am writing a class to represent time series data , i.e . basically a map of ( Instant , T ) pairs for a generic type TSome of the classes we deal with implement an interfaceand I want to provide a more convenient method in the TimeSeries interface to add such data items without stating the time explicity . Bas... | Generic parameter with additional constraint through intersection types |
Java : I have an mysql query : From this query I am getting no . of Full Day present.I have present_status= 'Half Day ' & present_status = 'Full Day ' in my database records . How to count 'Full Day ' + 'Half Day ' ? <code> SELECT count ( * ) as ` present_days ` FROM tbl_intime_status WHERE employee_status = 'Out ' and... | How to sum records of a single column with different possibilities ? |
Java : I launch a jetty instance indirectly when creating a JAX-RS endpoint using cxfThis works just fine , but how can i configure the size of the jetty threadpool minThreads and maxThreads programmatically when launching it via CXF ? <code> JAXRSServerFactoryBean sf = new JAXRSServerFactoryBean ( ) ; sf.setResourceCl... | Configure jetty that is launched via CXF programmatically |
Java : This question might be considered opinionated but I really ca n't seem to find a straight answer . So either I 'm missing something or I 'm asking the wrong questions.So , I 'm an undergrad student and new in the whole Spring app development and I 'm currently creating an app with React acting as the frontend an... | Is routing API calls through my own RESTful API considered an acceptable strategy ? |
Java : Why in the below code is assigning a value to the static variable acceptable but using that same variable is not ? <code> class Test { static { var=2 ; //There is no error in this line System.out.println ( var ) ; //Why is there an error on this line if no error on the above line } static int var ; } | Static blocks and variables |
Java : What are the norms for creating JPackage installer Java application on Linux ? I have created an installer for Windows , and am now creating one on Linux ( using Ubuntu ) So far I have : for creating a debian installer , it works ( installs not yet running properly ) but I am confused about a number of things , ... | What should linux-menu-group be when creating JPackage installer Java application on Linux ? |
Java : Given that 2 strings : I want to find out whether each character in stringB H A T S exists in stringAIn a junior approach , the process can be done within a nested for-loop which its computation complexity is O ( n^2 ) .I am looking for a faster solution to solve this problem . <code> String stringA = `` WHATSUP... | Find whether each character in 1 string is exist in another string , faster than O ( n^2 ) |
Java : C # 's extension methods are great for adding syntactic sugar . Java extension methods are great for allowing library developers to add methods to their interfaces.I am a non-library Java developer and know I will reap a lot of benefits from getting new functionality from libraries , but I would still like to ha... | Will Java have a way for non-library developers to use extension methods ? |
Java : I am writing my own Array List . Here is the remove method of the same , Now i will perform some remove operationNow this will result in the following output , But when i use the ArrayList from the API , i will get the output asAm i missing something ? Can someone please explain me where i went wrong . <code> pu... | remove ( ) in ArrayList |
Java : I need to extend an abstract class which I can not modify : With a generic class like this : My question is obvious : what should be returned by VerticalCheckBoxSelect : :getType to be compilable ( and correct ) ? <code> public abstract class CustomField < T > extends AbstractField < T > implements HasComponents... | Class abstraction and generics |
Java : Let 's say I have simple class : I have multiple pojo classes in my project and I want to be able to serialize each object to json . So I created new Serializer class ( gson used to serialize ) : And my example class extends Serializer : And I am able to serialize any object of class extending Serializer by call... | Java - pass type to superclass static method |
Java : Recently I was reading the following piece of code from oracle collection tutorial when i came across this piece of code.I was not able to understand why the returned value is something <code> public static < E > Set < E > removeDups ( Collection < E > c ) { return new LinkedHashSet < E > ( c ) ; } < E > Set < E... | generic return object |
Java : I would like to pass a reference to a primitive type to a method , which may change it.Consider the following sample : The output running the sample is : Which means int_ref was past to the function by value , and not by reference , despite my optimistic name.Obviously there are ways to work around this particul... | A reference to primitive type in Java ( How to force a primitive data to remain boxed ) |
Java : I was experimenting on initialization order in Java and I came across something really confusing : As you can see , we can not reference a field that was not declared yet , hence the compile error on System.out.println ( staticField ) ; in the first static block : Can not reference a field before it is defined.H... | Why does assignment in static init block compile without error ? |
Java : I 'm trying to figure out the whole Java generics topic.More specifically this issue : How can I add an `` extends '' wildcard specifying that the set method can receive E or any inheriting class of E ( in which case the Node will hold a upcasted version of the parameter ) .Or will it work even if I leave it the... | Parameters of a Java generic method |
Java : case 1 : it can work when using for-each loop：orcase 2 : it will catch compile-time errorIn case 2 , I know the variable i is not effectively final because its value changed between loop iterations . But I can not understand why the lambda can work in case 1 . <code> private void m10 ( String [ ] arr ) { for ( S... | Why is the loop variable effectively final when using for-each ? |
Java : I have to `` translate '' codes with a conversion table like this : My first idea was to use a Map associating each symbol to its translation and to load the table from a database or a text/xml file . Is there a better way ? Does n't have to be lightning fast , just easy to maintain and test.TIA . <code> | symbo... | How to convert/translate information ? |
Java : Java supports pass by value ( always works on a copy ) but when you pass a user defined object then it changes the actual object ( kind of pass by reference but no pointer changes ) , which I understand but why the changeObject2CLEAR method below is actually changing the value of the object ? Instead it has to w... | Issue with pass by value in java |
Java : In a program I was working on , I ran into a data storage issue , specifically related to ArrayLists . This is not the actual code I was testing , but it provides an example of what I mean.If you run it , you get , true , true , and false . The code recognizes that both are equal to 129 but for some reason retur... | Does == comparison use byte in ArrayList comparisons ? |
Java : First , a bit of context code : The above represents the data structure I am dealing with . I have an outer map ( key type is irrelevant ) , that contains inner `` property maps '' as values . These inner maps use strings to lookup different kind of data . In the case I am working on , each v1 , v2 , ... represe... | Is there a way to collect a map using `` groupingBy '' for MULTIPLE elements within a nested structure ? |
Java : when I am runnig the code in unix system.exit ( Integer.parseInt ( e.getMessage ( ) ) ) is giving 254 output : <code> System.out.println ( Integer.parseInt ( e.getMessage ( ) ) ) ; System.out.println ( e.getMessage ( ) ) ; System.exit ( Integer.parseInt ( e.getMessage ( ) ) ) ; -2 -2 254 | why I am getting two different values from system.out.println ( ) and system.exit ( ) ? |
Java : Here are three sample lines from my dataset : I am trying to come up with a pattern matcher which would capture the following : feature namethe relation ( = , > = , < ) feature value ( could be a mix of numbers and/or characters , but never contains a colon ) result ( the value that comes after the colon and bef... | Java - Pattern matches but fails to capture |
Java : I change a value that is used to determine when a while-loop terminates in a seperate thread . I do n't want to know how to get this working . If I access the variable test only through synchronized getters/setters it works as expected..I would have expected , if some read/write commands are lost due to concurre... | Strange behavior in Java with unsyncronized access in a multithreading program |
Java : How can I get type safety for a set of classes when there are cyclic relationships . I have 3 classes , Router , Interactor and Component such thatI want to ensure that a specific router is tied to a specific component and specific interactor.Edit The architecture of the app ensures that we have exactly 1 router... | Java Cyclic Generics |
Java : My code : As you see , in line x , T have to be String.class and returns String . But compile failed without casting the result to T. Change line x to return new String ( `` abc '' ) ; results Incompatible types . <code> private static < T > T get ( Class < T > clazz ) throws IllegalAccessException , Instantiati... | Why I must cast to Generic Type T even if I know it returns correctly ? |
Java : I have this code : I know I can declare a function which hold lambda : I want to make this function to hold implementation of Runnable from new Thread.But I do n't know what to put between < > of Function . <code> new Thread ( ( ) - > { //do things } ) .start ( ) ; new Thread ( ( ) - > { //do same things } ) .st... | Function which hold implementation of Runnable |
Java : I was posting an answer to a different question , when I came across a little mystery . The class definition ( slightly modified from the original questioner ) is here : In main , we then create a new Playground , Playground < String > animals = new Playground < String > ( 5 ) ; and put some animal Strings in it... | Array return can be used in assignment , but not in loop |
Java : I encountered the following behavior while using a ByteBuffer . It looks like a bug to me , but perhaps I 'm using the libraries incorrectly.Code : Output : What 's the deal with the leading space ? Am I doing something wrong ? Is this expected behavior ? If so , why ? <code> public static void main ( String [ ]... | Why is the first character in the CharBuffer returned by ByteBuffer : :asCharBuffer always a space ? |
Java : If multiple fields are declared in a single statement using a field annotation , does the annotation apply to all of the fields ? For example , will the following result in x , y , and z all having the @ Nullable annotation ? I 'm looking for an official specification on this , but have had trouble finding one .... | Do annotations apply to all variables in a declaration statement ? |
Java : Should defensive copies always be made for object references of mutable objects passed to constructors ? If yes , then how 'deep ' should I go in making copies . In the following example should I make deep copies inside copy constructors of all classes involved ? Eg:3.. What if some class forgets to implement de... | How deep should copy constructors get |
Java : How could I parse the following String to a LocalDateTime-Object ? 20200203092315000000I always get the following exception but I did n't understand it : My application code looks like : <code> java.time.format.DateTimeParseException : Text '20200203092315000000 ' could not be parsed at index 0 at java.time.form... | How do I parse an ISO-8601 formatted string that contains no punctuation in Java 8 ? |
Java : Fianlly , the console prints a NullPointerException error . The CoreJava says that we should n't modify the Collection which will return back to the stream after modified . And I do n't have a clear understanding of the principle . <code> List < String > list = new ArrayList ( ) { { add ( `` apple '' ) ; add ( `... | Transfer a List into a Java Stream , and then delete a element of the List.Some errors occur |
Java : I 'm installing a production Crafter 3.0 instance built from source , using the current documentation as guidance . However , I 'm having issues at this point : I ca n't find the INSTALL_DIR/apache-tomcat/solr-crafter/conf/solrconfig.xml file , and solr itself seems to be in different path . <code> Change the pa... | In CrafterCMS , how do I configure Solr in Crafter 3.0 ? |
Java : Is there any difference among case1 , case2 and case3 ? Is there any advantage or disadvantage related to performance ? <code> public class Test { private String name ; public void action ( ) { name = doSome ( ) ; // case 1 setName ( doSome ( ) ) ; // case2 this.name =doSome ( ) ; // case3 } public String doSome... | Java Variable setting |
Java : My code is : '' solveIt '' method returns after 30 seconds and until it returns , frame is n't installed properly but after solveIt method returns , the frame gets installed properly but what i want is that before going into solveIt method , the frame should be properly on the screen . Is there any method that c... | JFrame is loaded late |
Java : I am new to OODP , I am trying to have a method that is able to take in any kind of List data so that I can abstract things out . How can i do this ? <code> public abstract class CommonClass { abstract void send ( < what should i put here ? ? ? > ) { } } public class ClassA extends CommonClass { void send ( List... | Abstract method with different parameters Java |
Java : Consider the following visitor for a simple language interpreter.For completeness I add some code that gives necessary implementation details ( you can skip and read directly the question ) .a var statement is defined like that : a valid language instanceAn abstract way to represent the VarStat node is the follo... | Is skipping `` accept '' where type is known , a valid optimization for the Visitor pattern ? |
Java : Can the AdditionalBound described in JLS8 cast expression be used for casting anything except that a lambda expression or a method reference ? It is said , that it could be : and that : The target type for the casting context ( §5.5 ) introduced by the cast expression is ( ... ) the intersection type denoted by ... | Using of AdditionalBound in cast expressions |
Java : A new feature of Java 9 is that it can not only forcefully kill processes ( in the meaning of SIGKILL ) it had created but it may also support to send a SIGTERM ( in Java called `` normal termination '' ) .According to the documentation of Process one can query if the implementation supports this : public boolea... | Any VM supporting Process.supportsNormalTermination==true ? |
Java : I 'm trying to teach myself Java Networking . I tried to write a little WebChat-Application and it runs just fine when I 'm trying to run it in Eclipse , but when I 'm trying to run it in Debug-Mode I keep getting this error : I tried to fix it but I failed many times ... This is my code : <code> Thread [ AWT-Ev... | NullPointerException at Thread AWT-EventQueue-0 ( File. < init > ) |
Java : Say I have this : my question is - how can I define the thread that 's used in the pool , specifically would like to override the interrupt method on thread ( s ) in the pool : <code> class Queue { private static ExecutorService executor = Executors.newFixedThreadPool ( 1 ) ; public void use ( Runnable r ) { Que... | Override interrupt method for thread in threadpool |
Java : I am creating JDBC Statements and ResultSets.Findbugs rightly points out that I do n't close these if an exception is thrown.So now I have : ( Only I have rather more result sets and prepared statements and so on open ... so my nesting of finallys is rather deeper ) There has to a better way to ensure a large nu... | Ensure objects are closed if an exception is thrown |
Java : I have a generic class with this definition : Where AntColony goes this way : And Ant goes like this : I was hoping to extend AntColony in this fashion : But Eclipse is showing an error on the FlowShopAntColony parameter class : Which confuses me , since FlowShopAntColony is defined this way : And AntForFlowShop... | Java generics : Bound mismatch |
Java : In Java , is giving 4 as an output and notas expected by me . <code> 4 % -8 -4 | Why is 4 % -8 equal to 4 ? |
Java : For some reason I do n't understand why this code prints true and false , what is special about array that it does not include that annotation here ? It works as expected if you use getParameters instead . <code> import java.lang.annotation . * ; @ Retention ( RetentionPolicy.RUNTIME ) @ Target ( { ElementType.T... | Why getAnnotatedParameterTypes does not see annotations for array type ? |
Java : My mystery begins like this . Consider this bit of code : If you look past most of the scaffolding ( I just wanted to make sure it 's minimally complete and you can run your compiler on it ) , you 'll see in the middle there 's an annotation , and it takes a String array initializer , and there 's a comma after ... | Java : ever seen a compiler or tool that REJECTS a final comma in array initializer ? |
Java : It 's not exactly as the title says , but close to . Consider these Spring beans : Important note : I 'm using JDBC transaction manager that supports savepoints.What I 'm expecting this to do is , when EvilException is thrown , the transaction of the BeanA is rolled back , which with this setup happens to be the... | Rollback for doubly nested transaction bypasses savepoint |
Java : I have two separate entities : and Where andGenericValidator is an abstract class having a number of subclasses I would not like users to access directly . How should I handle those things better ? I do n't understand when it 's better to create a class likeinstead of implementing the Validatable interface as I ... | Using FactoryMethod pattern |
Java : Which are the default modifiers for x and m in ? I suppose that the code above is equivalent to : where the modifiers public and public static final are redundant , but I did n't find an official explanation for this.I was looking here : https : //docs.oracle.com/javase/8/docs/technotes/guides/language/annotatio... | Which are the default modifiers for fields and methods in a Java annotation ? |
Java : Just to give you a background which probably has nothing to do with the question . Trying to use the JAHMM library to build and score HMM's.One of the parameters to the functions mentions the above as the datatype and I have no idea what it means.From what I understand with help from a friendList < ? extends Obs... | Confused by the following data type |
Java : Why when I use reference this in a variable declaration , illegal forward reference does n't appear ? What 's the difference between declaration with this and without it ? The following example fails to compile because of the illegal forward reference : By qualifying the use of b by this the compilation error go... | Problem with illegal forward reference in Java |
Java : In String functions like substring ( ) returns helwhereas 0-3 index includes helland in regex Matcher 's end ( ) methodreturns 4 whereas first match ends at index 3I 'm just curious about why java works in this way <code> `` hello '' .substring ( 0 , 3 ) mat = Pattern.compile ( `` test '' ) .matcher ( `` test ''... | Why Java uses one past index for upper bound in string operations ? |
Java : I am recently started using java stream and write a one User service , which returns a stream of users . Using that user stream , I process other logic . Following is the piece of code that I am dealing with stream and it works fineBut when I start writing Junit then it fails with following error message.Here is... | How to write Junit for Java Stream |
Java : I needed to dig into the specifics of method invocation in Java , and while reading the section Choosing the Most Specific Method in The Java Language Specification ( Java SE 12 Edition ) , I found that ( 1 ) during invocation multiple methods can be maximally specific and that ( 2 ) having multiple maximally sp... | Example of multiple maximally specific methods that does not result in a compile-time error |
Java : If i change the byte to int I get a compiler error . Could you explain the problem ? <code> public class A { protected int xy ( int x ) { return 0 ; } } class B extends A { protected long xy ( int x ) { return 0 ; } //this gives compilor error //protected long xy ( byte x ) { return 0 ; } // this works fine } | Why do I get a compilation error when I try to have two methods with the same name and parameter type ? |
Java : Why is it that trying to catch an exception that will not occurr , will give a compilation error , whereas I can throw any Exception , it wo n't give an error ? Both can be checked at compile time , so it would just make more sense to me if the behavior is the same ? In the given example , the catch-block will g... | Why can you throw a non occurring exception but not catch it |
Java : I am creating an Android application . I am new to android . I want to create a label like in the image below . Here is the below code that I have tried.I have labels over the images . Any help will be appreciated . Thanks <code> < FrameLayout android : layout_weight= '' 1 '' android : layout_gravity= '' center ... | android custom user interface |
Java : I 'm solving a Project Euler Problem 14 using java . I am NOT asking for help solving the problem . I have already solved it , but I ran into something I ca n't figure out.The problem is like this : The following iterative sequence is defined for the set of positive integers : n = n/2 , if n is even n = 3n + 1 ,... | Use of integers and doubles give different answers when they should n't |
Java : Suppose I am modelling different animals in Java . Every animal has some combination of these abilities : walk , swim and fly . For the example , the ability set is constant . I can store this information as getters that return constants . For example : The run-time check is then : Or I can use `` tagging '' int... | In Java , should I use getters or interface tagging for constant properties ? |
Java : I would like to know how can I get all the elements from a collection containing a specific value.Like this : But I would like to filter the collection directly . I read that I can do this using LAMBDA , example : But I Do n't know how to apply this example.Thank you . <code> @ Overridepublic Collection < Sale >... | How can I filter directly a collection based on a value ? |
Java : I found this in some code I wanted to optimize . Here is the snipet : Then I decided to use the regex wisely and I did this : Then a friend told me to do this instead : Since I like to know the result of my changes I did a test to verify if it was a good optimization . So , the result with ( java version `` 1.6.... | Is this normal Java regex behavior ? |
Java : why my thread ca n't be stopped ? ? ? if i use rp.num == 0 , the thread can be stopped immediately . But , why when i changed the rp.num == x ( x is any number greater than 0 ) the thread can not stop ? please help me solve this thing ... thanks for any helps . <code> class Threadz { class runP implements Runnab... | Thread can not stop |
Java : While going through the libgdx source code for a Stage , I encountered this segment : ( Link on GitHub . ) What interested me was this line : Batch batch = this.batch ; My first guess was some caching improvement . Am I right , or is there another reason to avoid using the instance variable directly ? <code> pub... | Java Local reference over instance variable |
Java : Can anyone explain how this code snippet works ... The actual code itself is not relevant as it was from a short tutorial on using an MVP pattern for Android.My main question is how this code structure works and whether this is an inner class , of sorts , or maybe a transaction.. I have n't seen a code structure... | Is this an Inner Class |
Java : Given AGenericClass declared as below : What are the differences between variables a , b , and c ? a b and c all are declared without complaint from the IDE , but they all behave differently when setSubject is called . <code> public class AGenericClass < T > { T subject ; public void setSubject ( T subject ) { t... | How do these three parameterized variables differ ? |
Java : Same regex , different results ; JavaJavaScriptI ca n't understand why this is the case ? <code> String regex = `` Windows ( ? =95|98|NT|2000 ) '' ; String str = `` Windows2000 '' ; Pattern p = Pattern.compile ( regex ) ; Matcher m = p.matcher ( str ) ; System.out.println ( m.matches ( ) ) ; // print false var v... | Same regex have different results in Java and JavaScript |
Java : I am trying to call a java method which takes List < Class < ? > > from scala . The compilation fails with I tried using JavaConverters but get the same error.Java method : Calling from Scala : <code> type mismatch ; found : java.util.List [ Class [ T ] ] where type T < : Person.type required : java.util.List [ ... | How to call java method taking parameter as List < Class < ? > > from Scala |
Java : The question might be foolish as intern has no major usage here , still I am confused about the fact , why does b == c results true.Whenis executed , String b references to object having `` bc '' Does b.intern create the literal `` bc '' in String Constant pool , even if it does , how come b==c result in true ? ... | How does intern work in the following code ? |
Java : At first glance I thought the following makes sense : And it compiles properly so everything seems A-OK.But then I thought about it some more , in the context of erasure , and it seems to me that the Test interface gets erased to this : So how is Impl still able to implement Test ? <code> interface Test < T > { ... | Why does erasure still allow overriding/implementation ? |
Java : I am considering this from the Java Language Specification : If the catch block completes abruptly for reason R , then the finally block is executed . Then there is a choice : If the finally block completes normally , then the try statement completes abruptly for reason R. If the finally block completes abruptly... | Java - detect whether there is an exception in progress during ` finally ` block |
Java : Hi , the code above gives an error like that : Multiple markers at this line - str can not be resolved to a variable - Syntax error on token `` String '' , AssignmentOperator expected after this tokenWhy there is an error like this ? Of course I know str will be unreachable after defined . But java does n't give... | non-braces if block variable definition gives an error |
Java : I am somewhat mystified by the output of this program : Here 's what it outputs : It appears the compiler is `` promoting '' an object of type Integer to Long , just as it would normally promote primitive values . I 've never heard of object promotion and this behavior seems very surprising.My question : is this... | Does the Java JLS specify promotion of primitive wrapper types ? |
Java : I want to make a method that accepts any class T that implements any interface I.Then do something with the class and return the interface I that is implemented.Here 's what I 've tried : I 'm then creating an interface and a class which implements that interface : However , when I 'm calling the method referenc... | How to return interface from generic class implementing the interface ? |
Java : I try to find the current Browser for an specific Hack in GWT.like : ( View-class ) <code> if ( GWT.getBrowserName ( ) .contains ( `` IE '' ) ) { // DOM.setElementPropertyBoolean ( ... Hack } else { // normal stuff } | GWT Browser distinction in Client |
Java : In the book `` Core Java Volume 1 '' that I am reading it says the equality should n't work with inheritance . So , I have the following example which seems to have something wrong going on : http : //ideone.com/PhFBwGIt returns `` Equal '' for both symmetrical comparisons which presumably it should n't . Is it ... | What 's wrong with using Inheritance Equality in Java ? |
Java : In this case , I need to explicitly convert a+b to byte like this : It 's the same with short : Otherwise it gives an error.But in case of integers , it 's not required to convert explicitly : This will work just fine.Why is that ? We do n't need to explicitly cast even in the case of long as well . <code> byte ... | Why is there no need to explicitly cast in case of integers ? |
Java : I am getting below output in following format , which is default I think.But I want to change this format as below.Below code I am using in java class.How can I rearrange the json format ? For more understanding , pasting above method with simple syntax.Sample Code Method.. <code> { `` count '' :100 , '' sum '' ... | How can we customize order of count , avg , sum , min and max in DoubleSummaryStatistics object in java8 |
Java : The traditional way to iterate over an ( integer , in this example ) array of elements is the following : However , does this mean that after each iteration 'array.length ' is re-evaluated ? Would it not be more efficient to do this ? : In this way , ( to my understanding ) the program only has to calculate it o... | Is there a difference in runtime efficiency if I evaluate the size of the array outside the loop ? |
Java : I 've read everywhere that if a field is used at the same time by different threads , some sort of synchronization is needed , and that if it is used by only one thread , it 's not needed . But what if it 's used by different threads , but not at the same time ? Let 's take a code like this : MyRunnable is : Is ... | Is it safe to use an object in different threads , but NOT at the same time ? |
Java : Say I have a method : but sometimes when I run this method , I do n't need to synchronize on anything.What is a good pattern to conditionally synchronize on something ? The only pattern I can think of is a callback , something like this : is there another way to do it , without a callback ? <code> public void ru... | Conditionally define synchronized block |
Java : Straight out from Java concurrency in Practice : The above is a Thread-safe class : since its setters are synchronized.I understand also why the getter does n't individually return x / y but instead returns an array . I have 2 questions .Why ? private SafePoint ( int [ ] a ) public SafePoint ( SafePoint p ) { th... | Multithreading private constructor |
Java : I often find myself doing something like this : where f is a computation intensive function . This requires twice as many evaluations of f as are actually necessary . I 'd prefer to but then I do n't know how to get the original element that this minimum corresponds to.One ugly way around this isand thenIs there... | Find pre-map element in stream corresponding to post-map minimum |
Java : I was answering this question , where I recommended utilizing exports to syntax to prevent external consumers from accessing code that is intended for internal use between modules.But on further reflection , the only real safety checking that modules implement is that it matches the name . Consider this example ... | Securely Export Packages to Java Modules |
Java : I am trying to write the Data Structure for a Hash Table using Chaining . When i remove the keyword `` static '' from the nested class , i get the error that `` Can not create a generic array of SeparateChaining.Node '' ? on the line where i allocate memory to hmap using new.With the static keyword it works fine... | For a Generic outerclass , why do i need to declare the nested class static ? |
Java : I am experimenting with DateFormat and I 've come across an issue where I 'm creating a date , storing it as a string and then parsing it back into a date and somehow ending up with the same date but a different day of the week.I get the output ; If I make the number of milliseconds in d1 smaller then when the d... | Why is there a 1 day difference in these dates ? |
Java : I followed an instruction to trigger the JavascriptInterface from a webview , but it isnt triggered in my case.I have an class QuickTextViewer with following : I also added the following to proguard-rules.pro ( actually public only for testing ) In my case onPageFinished is triggered but resize ( ) not ! Any sug... | triggering JavascriptInterface from a android webview |
Java : I was using LongStream 's rangeClosed to test the performance of the sum of the numbers . When I tested the performance through JMH , the result was as below.The difference between rangedReduceSum and rangedSum is that only the internal function sum ( ) is used . Why is there so much performance difference ? Aft... | Why is there a difference between LongStream reduce and sum performance ? |
Java : We have a Student class as follows : We have a LIST of Students as follows : This List needs to be converted into a HashMap < String , Integer > such that : the map does not contain any duplicate Studentif a duplicate student name is found , his marks shall be added withthe previous occurrence.So the output shou... | Transform a List < Object > to a Map < String , Integer > such that the String is not a duplicate value using Java 8 Streams |
Java : I have the following collection : Here 's sample data : Since I know all enums , I want to convert it to the list of POJO . The definition of the object is as below : I have tried different solutions , like with mapping inside mapping : Unfortuantely , what I am getting is List < List < SomeClass > > . Is there ... | Convert Map < ? , Map < ? , ? > to List of Objects |
Java : I have a question , a little bit theoretical : Assume , I have the following classes : The second report needs an additional parameter release to work properly , but my interface is defined without parameters for execute method , so I work around it with a setter method , so it would look like : So I do n't like... | Java - Getter/Setter , behavior and Interfaces |
Java : What am I looking for ? Let 's consider int a = 5 for exampleIts binary is : 101So when we dothen the rightmost bit , i.e. , 1 in this case , would drop off , I want to catch it in some variable..i.e. , In this case I have a hard-coded value but it can be any arbitrary user input for number.If I do b = a > > 1 t... | Catching the `` dropping '' bit value |
Java : Consider an object which produces data that is consumed by another object to generate a result . The process is encapsulated in a class and the intermediate data is not relevant.In the example below , the process takes place on construction and there is no issue . The type parameter on the constructor ensures co... | Enforce class fields to be same generic type without specifying a class type parameter |
Java : There is a Spring-MVC project in which there are three types of users : Customer , Admin , Cook . All of them are inherited from the class User . Roles are created without ENUM , simply through static String constants ( shown in the User class ) . After I added Spring Security , authorization is successful , but... | Why the application does not see the Roles in Spring Security ( Forbidden ) |
Java : I know that HashSet < String > data structure can store unique strings and say if string is present with O ( 1 ) complexity , because it uses hash code . Can the same complexity be achieved , if I want to ignore letter case ? Next use case should work : Is it possible to implement such data structure ? <code> Se... | Data structure that stores strings and ignores letter case |
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