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Java : I am building some static analysis tools to help manage the architecture of a large project . For this I am doing a couple of regexes to parse information from Java files . One of these regexes is used to scan for an @ WebService ( ... ) annotation . I was wondering if there is a situation possible where there a... | Is there ever a reason to have parentheses within an @ Webservice ( ... .. ) annotation in Java EE ? |
Java : I 'm debug ( Shift + F9 ) the method offer ( E e ) of JDK8 API 's java.util.concurrent.ConcurrentLinkedQueue , i found IntelliJ IDEA will change the field head of this queue soundlessly in the process of debugging , but the run schema ( Shift + F10 ) will not change the field , why ? and there 's no code change ... | Why my object has been changed by IntelliJ IDEA 's debugger soundlessly ? |
Java : I would like to split a string into several substrings , and I think using regular expressions could help me.Note that the curly brackets and comma 's are just a visual aid . It does n't really matter what the final form is , just that the values are seperately accessible/replacable . Thanks in advance . <code> ... | Split a string into several substrings using regex . Both matches and non-matches should be returned |
Java : Here 's the code : It 's a snippet from the book Java Concurrency in Practice , and I 'm thinking about that maybe the counter reservations is unnecessary as we could simply use queue.size ( ) to get the number of elements in queue.Am I right ? <code> public class LogService { private final BlockingQueue < Strin... | Can I use Collection.size ( ) to replace the counter in this code ? |
Java : This might be a really elementary question but it puzzles me at this stage of my Java learning.I have got the following piece of code : If I move the line that instantiates the ArrayList object and the calls on that object outside the method , the line that creates the object is fine but the add ( ) method calls... | Calling a method on an Object from within a Class vs from within a method |
Java : I just noticed that binaries in bin in an old JRockit JDK 6 on CentOS 6 , OpenJDK 8 on Ubuntu 18.10 and Oracle JDK 11 on Windows 11 have approximately the same size.This seems odd since they nothing in common in the tasks they fulfill ( e.g . wsimport and xjc ) . Diffing a hexdump shows that the binaries only di... | Why do almost all Java binaries have the same size |
Java : How can I do that ? <code> public class ActivityTest extends Activity { public EditText edtText ; @ Override public void onCreate ( Bundle savedInstanceState ) { super.onCreate ( savedInstanceState ) ; setContentView ( R.layout.test ) ; WebView webView = ( WebView ) findViewById ( R.id.webView ) ; webView.loadUr... | Change text of the edit text by html |
Java : I 'm making a billiards game in Java . I used this guide for collision resolution . During testing , I noticed that there is more velocity between the two collided pool balls after collision . The amount of extra velocity seems to be 0 % -50 % . About 0 % on a straight shot and 50 % on an extremely wide shot . I... | combined velocity is larger than initial velocity |
Java : How can I get the values of an `` enum '' in a generic ? On the other hand , I can query the values ( ) for Enum class : <code> public class Sorter < T extends Enum < ? > > { public Sorter ( ) { T [ ] result = T.values ( ) ; // < - Compilation error } } enum TmpEnum { A , B } public class Tmp { void func ( ) { T... | How can I get the values of an `` enum '' in a generic ? |
Java : I m not getting the whole data sometimes while reading the inputStream like this ( somtime full data is recieved ) .should i read the input Stream until inputStream.available ( ) is zero.. ? Data in inputStream is large.Plz Suggest some altenative with Sample code <code> private String readInputStream ( InputStr... | Not getting whole data while using available ( ) |
Java : We recently faced a bug in our code which was basically related to OOPs concepts . Output : ABC @ 642c39d2Should n't this raise a run time exception ? Can someone point me to the correct direction as to why does n't this code raise an exception ? <code> class ABC { String a ; ABC ( ) { a = `` abc '' ; } } public... | Type casting an object to any Collection type |
Java : Suppose I have a class called CommandLineOperation . This class accesses API resources . Thus I have defined one instance member of type APIAccessor.The operations in CommandLine , are infrequent , is it a better approach to instantiate APIAccessor under every operations or create once using constructor of Comma... | Coding Pattern for use instance member |
Java : A service interface declares two methods which apparently do the same processing : The service above is being called like below : Which one of the service methods are going to be called and why the compiler does not complain about an ambiguous call in this context ? <code> interface Service < T > { < R > R proce... | Why Java is not complaining about an ambiguous call ? |
Java : Help me please to undestand why i ca n't call the testSuper ( ) method ? There is compile error : But the testExtends ( ) method OK . However , it looks the same . <code> The method testSuper ( Group < ? super BClass < ? > > ) in the type Group < BClass < String > > is not applicable for the arguments ( Group < ... | Unbounded wildcards with extends and super as parameters |
Java : So someone asked Is the ++ operator more efficient than a=a+1 ? a little while ago . I thought that I analyzed this before and initially said that there was no difference between a = a + 1 and the incremental operator ++ . As it turns out , a++ , ++a and a += 1 all compile to the same bytecode , but a = a + 1 do... | Analysis of various incremental operators vs assignment and incrementing |
Java : I have list of Payments : I created a function that takes in this list and currentDueDate.If paymentDueDate is equal to or before currentDueDate and one that 's closest to currentDueDate , I want to use that row in my calculations.For some reason my sort is not working properly.Can someone shed some light on wha... | Sort List of objects by date and applying filter |
Java : There are many immutable classes in Java like String and primitive wrapper classes , and Kotlin introduced many others like Range subclasses and immutable Collection subclasses.For iterating Ranges , from Control Flow : if , when , for , while - Kotlin Programming Language we already know : A for loop over a ran... | Will immutable objects with const parameters be optimized to be instantiated only once by the Kotlin compiler |
Java : I am trying to collect result of a list and organise them into a Map where the value is a Map : I get java.lang.IllegalStateException : Duplicate key error as getProcessedDate ( ) is same for different values in the list.Is there a way I can merge multiple objects with same processeddate into the map ? e.g say I... | Java 8 Stream function grouping to Map where value is a Map |
Java : Given this Java code : The expressions initializing list , list2 and list3 work fine . However , the expression initializing list4 breaks with this error in Eclipse : and this error in javac : But AbstractMap.SimpleEntry directly implements Map.Entry . So why does type inference break for list4 when it works for... | Why does Java type inference for generic supertypes break here ? |
Java : I need to use lambdas to generate some lists of new objects . These new objects inherit some of the traits from the existing ones . Since it 's hard to describe it without going into too much delicate details , I 'll use an example of a parent and their children . I want to generate a list of kids based on a lis... | Java - getting a list of new objects from a stream based on the list of the existing ones |
Java : I 'm writing a Swing application and trying to make a menu where each menu item has its own action : Here 's how I wanted to solve this : However , I can not use loadGame ( i ) , because it says i would have to be final . I understand the reason for this , but I do not know how to work my way around it . <code> ... | How do I solve local referenced variables inside a for loop ? |
Java : I want to use streams like : but stop the filtering as soon as I have maximum 100 Elements ready to be collected . How can I achieve this without filtering all and calling subList ( 100 , result.size ( ) ) ? <code> List < String > result = myArr .stream ( ) .filter ( line - > ! `` foo '' .equals ( line ) ) .coll... | Java Streams TakeUntil 100 Elements filtered/collected |
Java : Given a class T which is a subclass of U , is it safe to cast Iterator < T > to Iterator < U > ? And assuming that the cast be safe , are there more elegant ( and warning-free ) ways of doing it other than : My reasoning why the cast is not dangerous is this : Iterator < ? > does not support inserting elements ,... | Convert from Iterator < T > to Iterator < U > where T is a subclass of U |
Java : This code : Gives such compilation error : From what I understand , E becomes ? extends Base , something that extends Base . So , why new Base ( ) ca n't be passed ? <code> public class Base < E > { static void main ( String [ ] args ) { Base < ? extends Base > compound = new Base < Base > ( ) ; compound.method ... | Why new Base ( ) can not be passed to < ? extends Base > ? |
Java : I have the following Java codeWhen the test is run , the assertion fails and exception is printed as standard output and the TestNG shows the test result as FAILED.If I catch the same exception usingthe exception is printed as error output and the TestNG shows the test result as PASSED . In both cases exception ... | What is the difference between handling exceptions by catch block directly parent class and subclasses |
Java : I am trying to detect which class inside a jar contains main or a supplied method name ( if possible ) .At the moment I have the following codeThis will allow me to get packages and classes under these packages , but I do not know if it is possible to even get methods inside classes.Further , I do not know if th... | detect main inside a jar using java code . |
Java : I have a string like this : and regex : I want to match all 6 groups separately , but when I match the pattern , I get result like this : How can I match each group separately ? <code> String text = `` new SingleSizeProduct ( 422056 , 1265858 , 5430 , '3XL ' , 75 , 0 , '14.90 ' , '16.50 ' , '29.90 ' , 'TL ' ) , ... | Java regex match each group separately |
Java : I was testing a program for CPU usage check and I got a null pointer exception , so I added null check . When I added null check I started getting series of errors . Here is the code : The Highlighted lines show the null check added . Compilation error after this null check is as follows : Please help in resolvi... | Adding Null check is throwing a series of compile errors |
Java : When I enter an expression in JShell ( 9.0.1 ) it comes back with : Where does the 22 come from and what 's happened to $ 1 to $ 21 ? ( They are undefined . ) I seem to vaguely remember ( when I started with Java 9.0 ) that the variables started with $ 1 , which made more sense . Now , with 9.0.1 , they all star... | JShell dollar variable name numbering |
Java : I want to do this : But then the first 2 lines in a single line like : But the first line fails . I get : incompatible types.Required : Foo.BarFound : Foo.BarWhy is that ? And the last class : <code> Foo < String > foo = new Foo < > ( ) ; Foo < String > .Bar fooBar = foo.new Bar ( ) ; fooBar.doSomething ( `` thi... | Required type is same as found type |
Java : Suppose I have some string , and run the following tests on it : How is it possible that indexOf finds the substring ( it does not return -1 ) , but the regular expression in the second test does not match ? I have come across this problem while trying to write a test that checks if taglibs are rendered correctl... | Substring is found , but regex fails |
Java : As a Java beginner I 'm playing around with a case statement at this point.I have set : int d = ' 1 ' ; And with : System.out.println ( `` number is : `` + d ) ; , this returns 51.Now I found out that if I set it as : int d = 1 ; , it does return 1.Now my question is why does it return 49 when I set it as ' 3 ' ... | Java CASE why do i get a complete differet int back with and without using ' ' |
Java : I need a clarification in Dynamic polymorphism of Java.Here when i create a child class object with a base class reference , while invoking the method f.display ( ) it gives me the output as in boo 8 . This is because of dynamic polymorphism which checks the object type at run time for invoking the method.Now wh... | dynamic polymorphism reference pointing to base class |
Java : I need some advice about usage of Iterable < T > in Java.I have the following class : I need to create a class ValidatorChain as follows : Maybe I should just override some instant implementation of Iterable < T > instead of writing my own one from scratch . <code> public abstract class Validator implements Comp... | Do I really need to implement iterator in that case ? |
Java : In my spring boot application , in my rest controllers , I successfully inject an instance of Authentication to get the session 's user information.However , in all of those controllers , I currently call a helper method like this : How can I reduce this code duplication ? <code> @ GetMappingpublic List < String... | How to inject the username ( not the Authentication ) ? |
Java : I have a code that iterates on some objects of type MyType : No I 'm adding a flow that handles result of type Map < Long , MyNewType > that needs to do exactly the same thing while the only difference is that the method that returns the status is named differently ( let 's say - getObjectStatus ( ) instead of g... | Java - Extracting code to a generic method when method names are different |
Java : I have a class that 's a multiton , so I know that given a particular key , there will never be two instances of the same class that exist . This means that , instead of : ... it 's safe for me to do this : The class is also final , so I know that nothing related to polymorphism could cause problems for comparis... | Annotating a Java class as safe for reference comparison |
Java : I always thought final keyword has no effect , performancewise , on local method variables or parameters . So , I tried to test the following code and it seems I was wrong : I checked the bytecode and they are not the same for these 2 methods . Decompiled code in idea looks like this : Why is there a difference ... | Java compiler optimizations with final local variables |
Java : While refactoring I came across the following method in a subclass : What are the benefits to keeping this method rather than simply allowing the inherited superclass method to be called ? <code> public void disposeResultsTable ( ) { super.disposeResultsTable ( ) ; } | Is there a benefit from having a subclass method that only calls the overridden superclass method ? |
Java : I decided to dig into source code a bit and noticed that Collections.synchronizedList ( List ) is implemented as follows : where the SynchronizedList nested class is : As can bee seen , the class useses a private lock object to provide thread-safety . But the documentation allows us to iterate over it using lock... | Is it safe to iterate over synchronized wrappers ? |
Java : Let 's say I have 3 classes A , B , C , and my Main.B extends A.I want to use a scanner in all of them include my main.should I move scanner by inheritance or should I use static and declare my scanner in my main ? I tried to look here but did not get a clear answer which is better : Is there any way I can use a... | Java static or inheritance variable |
Java : Thanks for all your help and sharing.My question is in regards of the Stochastic Search . This technique is used to do approximations of data through a defined amount of cicles over a , an in general , mathematical calculation . Please see following code , I tried to reduce it to its minimum . My expectation is ... | Stochastic Search to lambda expression |
Java : I have a code , which is working as required , but I want to re-write it in Java 8.This code will produce a map.Each list item will have all the servers allocated to it.OutputWhat would be the lambda equivalent ? <code> public static Map < String , List < String > > agg ( ) { List < String > list = Arrays.asList... | Possible way to write below code in java 8 |
Java : I have the following class : which throws exception in this line : Methods to create racer that consists in the same class : The Racer Class : Abbreviations.txt file : FileLoader class : I read about Stream Supplier but I ca n't figured It out so I will be grateful for any help how to fix my program . <code> pub... | stream has already been operated upon or closed , gained exception when trying to create Racers |
Java : Given : The compiler accepts transform ( known ) but complains : for transform ( unknown ) . I get the opposite problem for transform2 ( ) . I 've consulted PECS and I believe that transform ( ) is the correct method declaration but I ca n't for the life of my figure out how to get a single method to handle both... | What method declaration accepts bounded and unbounded multi-level Generics ? |
Java : I have tried passing a value between 2 methods by following different solutions on here , but passes null.The code I am trying to pass : Where I am trying to pass the value `` price '' to : The value of price in getPrice ( ) is what it is supposed to be but when I print out the value in recordData ( ) , the valu... | Unable to pass a value between methods in same class in Android |
Java : I have a bunch of files on a local file system . My server will serve those files . In some cases the server will receive an instruction to delete a file . At the moment I 'm using FileChannel.lock ( ) to acquire a lock on the file , this is mostly to make sure that some other process is n't editing the file whe... | Should I have a lock on a file when I want to delete it ? |
Java : Is there a correct way to open a resource for each element in collection , than use stream api , do some map ( ) , filter ( ) , peek ( ) etc . using the resource and than close the resource ? I have something like this : This should work fine , except I 'm opening a resource ( e.g . db connection ) in the getEle... | Is there a correct way to close resources opened in java stream api ( for each element ) ? |
Java : I expected that simple intermediate stream operations , such as limit ( ) , have very little overhead . But the difference in throughput between these examples is actually significant : I am curious : What is the reason for the quickly degrading throughput ? Is it a consistent pattern with chained stream operati... | Quickly degrading stream throughput with chained operations ? |
Java : While developing a two-dimensional vector class as part of a math library , I 'm considering having static and instance method pairs for stylistic and usability reasons . That is , two equivalent functions but one is static & non-mutating , and the other is instanced & mutating . I know I 'm not the first person... | Having pairs of static and instanced methods that perform the same tasks ? |
Java : I do not understand how the compiler handle 's the following code as it outputs Test while I was expecting an error.I was hoping someone could tell me the exact steps the compiler goes through when executing the code so I can understand the output . My current understanding is that : The compiler checks during c... | Unexpected adding String to List < Integers > |
Java : I have a class called User and a file called Users.csv , like below : User class : Users.csv : Also , I have a class called test , which implements a single method : test class : The problem is in the method readUsers ( ) . It is returning me an ArrayList where every element is the same , and they are the one at... | Why is this method returning an ArrayList with all the same objects ? JAVA |
Java : So I 'm building a test library that I will mainly use for personal use however I have a question.With Java , if you have 2 or more constructors in your class , if you wish to call one from another , it must be the first thing you do . This is problematic for me as I have the below setup.How can I do this , avoi... | Throw Exception then Call Constructor ? |
Java : I 'm trying to do clean and install on my Spring Boot project in before creating the Jar file for my project however I came across this errorI 'm new to Spring Boot and have never really utilized the test function of it . So my test class is pretty much default of how it was initially created with the project.My... | Spring boot Maven install error - Unable to find a @ SpringBootConfiguration |
Java : The above statement gives a warning `` Type safety : Unchecked cast from Class < capture # 5-of ? > to Class < ? extends MyClass > '' .This time I get an error , because of type erasure ... This time I know that the cast is safe , but the compiler does n't , and still gives the warning . ( If you ask me , the co... | Is there a way to cast a class to have specific parameters to the java.lang.Class < > generic ? |
Java : I 'm almost completely new to Java and programming in general ( my main degree is in Law but I 'm hoping to open myself up to programming as I truly believe it 's going to be an essential skill in a couple years ) .I 've created two classes , LabClass and Student , and the point is to enroll students into the cl... | Having trouble referring to a method in another class |
Java : I 've just started learning Java GUI and faced this problem while practicing event handling.Here 's the initial windowWhen I enter a number inside the text field it 's supposed to say whether the guessed number is higher , lower or matched . If not matched it 'd prompt for another number . But the window just ha... | What is wrong with this Java GUI code ? |
Java : I would like to transform a Map < String , List < Object > > so it becomes Map < String , String > . If it were just Map < String , Object > it is easy in Java8 ; But this will not work because getValue returns a List Map < List < Object > , String > in my example . Assume Object contains a getter to be used for... | Inverse Map where getValue returns a List |
Java : I have the CharacterEncodingFilter in place ( first filter ) in web.xmlBut when I make a POST request , the body does not get encodedReq Body Sent : But received as <code> < filter > < filter-name > encodingFilter < /filter-name > < filter-class > org.springframework.web.filter.CharacterEncodingFilter < /filter-... | Post body is not getting encoded even after adding filter |
Java : for a test I created following regex by mistake : I was puzzled that this regex really works and I ca n't explain the result : the result is : My ideas so far are that java tries to replace `` nothing '' between the characters but why not the characters itself ? \\w+ should match the ' H ' I would expect that ev... | Programming error leads to inexplanable regex |
Java : I 'm confused with the process of loading a class . What is the order in which members of a class are executed ? See the following : Whenever I move the declarations of a and b to the top before the static block , compilation works fine . So I need to understand how this stuff works to resolve the problem above ... | What really happens when loading a class in java ? |
Java : Suppose we have a prototype-scoped bean.We 're injecting this bean to a class , TheDependent.But there is also another one.In each @ Autowired , a new instance of Foo gets created because it 's annotated with @ Scope ( `` prototype '' ) . I would like to access the 'dependent ' class from the factory method , Fo... | Access the injectee component from bean factory |
Java : I am using Eclipse Kepler , with JRE 7 . In the buildRunner method - why I am able to see the this of Main ? What is the 'this ' of Main in a static method ? Why does this compile ? I can only do that if value is final . I can not call instance methods of Main and stuff , but value is not decalred static ! Furth... | Why am I able to print this field in a static method ? |
Java : There is a multidimensional String array being passed in as an Object.I 'm supposed to `` unfold '' it and process each of its primitive entries . There 's no way to know the dimensions other than by looking at the Object itself . The difficulty i 'm having is in casting . I can look up the array dimension by in... | How to cast a multidimensional array without knowing the dimension in Java |
Java : I have set of urls now i want to filter them out on the bases of web domains ( say wikipedia urls ) .Right now what i am doing is iterating set and for each url i am just finding a keyword of that web address.is there any other technique that is more efficient than my current approach ? <code> if ( ur.contains (... | How to filter URL on the bases of web domain ? |
Java : I was looking through an old codebase and I found a method that only calls its parent : Would there be any use case for such a method ? For me it looks like I could just remove it . <code> @ Overridepublic void select ( Object item ) { super.select ( item ) ; } | Overriding method only calls parent method - useful ? |
Java : I 'm using generics in Java for the first time , and I 'm facing an issue I do n't manage to overcome : why this compiles : But this does not : And I get this error : both methods have same erasure.I 'm sorry if this is a stupid question , but I do n't get why the order of interfaces in a bounded type parameter ... | `` both methods have same erasure '' error using bounded type parameters |
Java : I run the following Java code : The display is GMT+03:00 ! It seems that when we use timezones with ids such as Etc/GMTxx , the sign is reversed . Why ? <code> TimeZone tz1 = TimeZone.getTimeZone ( `` Etc/GMT-3 '' ) ; System.out.println ( tz1.getDisplayName ( ) ) ; | Strange behavior with Timezone |
Java : For example if I were to create the following class : If I were to create an instance of ExampleClass . Would that instance contain the code for the static method and/or field I created ? I have an object that will represent some data from a row in my database . I would like to create the a list of these objects... | Do Static Methods and Fields take up memory in an instance of the class they are defined in ? |
Java : I get a horrific stackoverflowerror , and figured it was my deep recursion causing it ( well , the debugger helped with that ... ) . Can anyone guide me in turning my recursion into a loop ? More specifically , return find ( getNextLocation ( startPos , ++stepNum , key ) , key , stepNum ) ; causes the recursion ... | How to turn recursion into iteration ? |
Java : This particular problem I 'm working on is listed as such : ConcatArrays ( int [ ] listA , int [ ] listB , int [ ] listC ) with no return type.1 . The method passes the formal array parameters listA and listB , then return the concatenated array listC.2 . The first part of listC contains elements which are the s... | Is it possible to concate two int arrays without using a return type ? |
Java : I 'm trying to receive data from a client and then log it onto the console.Here is how i do this : When it comes to printing my messageToPrint it actually repeats the last one , and reprinting it with a newer one.I 've figured out what is the problem though.If i put allocation of the array data inside the while ... | How can erase the contents of an array in Java with safety ? |
Java : I have just started to learn about Java Runnables and I have heard of Callables . However , I am very much struggling with this problem . I would like to make a method which takes a function as an argument ( whether that be as a Callable , a Runnable , or something else , as long as I can simply call the functio... | Make a Method Which Generates the x and y values of Another Given Function |
Java : I have a problem displaying a number of dates that are stored as longs.I create the date objects with the constructor that takes the long argument , and then print the dates to a PDF file.However , I have a problem with older dates , when running the program on Linux , compared to Windows.Take this date : 25. ap... | Older dates are parsed as summer time , even if that is not true in Java |
Java : I have a list1 containing different strings which start with a string from another list ( fooBarList ) .I would like to create a Hashmap < String , List < String > > hm which seperates the strings from the list1 depending on what they start with.Result should look like this : the fooBarList defines the different... | Assign all values in a Set < String > to a Map < String , String > with streams |
Java : I 'm sorting an array of `` Albums '' by the output of their method getAlbumArtist ( ) , using a custom comparator class , AlphaNumComparator , which has a method compare , which compares two strings . I have the following code , which works : This seems like the sort of code that could be simplified/made more c... | Is there a more concise way to write this method using Lambda Expressions ? |
Java : I am new in Java 8 , and I want to get the first Phone that is not null from a list of contacts form a list of persons , but I am getting a incompatible types error <code> return segadors .stream ( ) .map ( c - > c.getSegadorMedium ( ) .stream ( ) .map ( cm - > Objects.nonNull ( cm.getPhoneSegador ( ) ) ) ) .fin... | Java 8 : Getting a property from a List of a List |
Java : I was trying to create a method reference to an arbitrary object , so I defined the following types : Then I declared the method reference , like below : When I call : I get a NullPointerException : Can someone explain why this happens even though the Impl reference is not used anywhere ? <code> interface I { bo... | NullPointerException when calling a method reference to an arbitrary object with null argument |
Java : I wanted to learn parallel programming for speeding up algorithms and chose Java.I wrote two functions for summing long integers in array - one simple iterating through array , second - dividing array to parts and sum up parts in separated threads.I expected to be logical a roughly 2x speed up using two threads ... | Java multiple threads give very small perfomance gain |
Java : Here I 'm making a virtual proxy for a heavyweight object . Each time before calling HeavyweightObject : :operate , the program checks first whether the object is null or not . This part is checked once and only once through the entire lifetime of the object . A possible improvement maybe using the state pattern... | Does it makes sense to use state pattern with virtual proxies ? |
Java : The above code will convert the the whole array of integers into an array of Strings ( containing binary format of the input string ) , but there is a caveat.For Example : If the input array is : 2 3 7 10The binary string array will be:10111111010But I want the output array to be like the following:0010001101111... | How do I convert an array of integers to binary ? |
Java : More precisely , if there exists a function in the call stack with the strictfp modifier , will the function at the top of the call stack also adhere to the strictfp specifier ? In this example , foo1 and foo2 appear to return the same value . In other words , it does n't look like it matters whether the functio... | Does Java 's strictfp modifier apply through function calls ? |
Java : Let 's say we 've got the following classes : Why does the following assignment compile without any problems : but this one : fails with this compile error : Error : java : incompatible types : invalid method reference incompatible types : Event can not be converted to Service.ServiceEvent <code> interface Event... | In Java is it possible to assign a method reference to a variable whose class has a generic type ? |
Java : In Java , is there a generic way to embed the code of a method in a log by any means ? I am working in Cucumber and altough its tending towards ( or is ? ) bad practice , the compliance department wants to see the assertions behind a `` Then '' statement printed out in the report ( they cant access the source co... | Embedding contents of a method in a log or report |
Java : how to add 2 or more constructors ? ? i know the use of data class in kotlin , but i am not getting what exactly this keyword is in kotlin and why we have to put anything inside this ? I know kotlin but not that much.how i changedit gives me error to put something inside this . why we use this here and why we sh... | Add 2 or more constructors in kotlin |
Java : I discovered that classes with default equals method has differentinstances of meta object Method . Why is it so ? At first glance it looks not optimal because method objects are immutable . <code> class X { } Method defaultM = Object.class.getMethod ( `` equals '' , Object.class ) Method xMethod = X.class.getMe... | Why multiple instances of Method object are for the inherited methods |
Java : I 'm really hoping this can be solved in regex , but I fear not ... .I 'm looking for a regex that will return multiple matches of a term ONLY is another term appears in the same string . This is better explained with an example . Consider : I 'd like to match '144 ' , '424 ' and '345 ' only . ( Any 3 digit numb... | Regex to match multiple occurances IFF another string occurs |
Java : I have a requirement , where I have a string which is comma separated and then I need to read the individual value and create a collection of object using them.For example my string contains value like foo , bar , baz and then I need to create three object using them likeThere might be multiple spaces before and... | complex operation using stream api in java |
Java : I have list of arrays from which I am picking up a random one.I can print the random output . How to pass the output as xpath value ? ? <code> String [ ] Category = { `` abc '' , `` abc '' , `` abc '' , `` abc '' , `` abc '' , `` abc '' , `` abc '' } ; Random random = new Random ( ) ; int index = random.nextInt ... | How to add the output to xpath |
Java : While looking at some Java 8 code I saw some use of generics that I did n't quite understand , so I wrote my own code to emulate what was going on : Running this prints : Test_Child constructed with string 'Test'What I do n't understand is : Why do n't you have to provide arguments to Test_Child : :newHow callin... | Using Generics to Construct Instances of Child Classes |
Java : I want to update values of map1 so that it has entries : '' k1 '' , `` val1 '' , '' k2 '' , `` val2 '' , '' k3 '' , `` val3 '' My solution : Is there any better way to do this ? Edit : I am using Java 7 but curious to know if there any better way in Java 8 . <code> Map < String , String > map1 = new HashMap < > ... | Updating Values in Map on the basis of other map in Java |
Java : I 've stumbled across some code that is broadly along the following lines , but can not for the life of me fathom why the author is attempting to remove bar from bars before then adding it : All that I can come up with is that it 's in anticipation of ( or legacy from ) a different Set implementation that 's sen... | What possible reason could there be for removing an element from a HashSet immediately prior to re-adding it ? |
Java : I 'm studying for a Java exam and came across the `` unreachable statement '' compiler error , e.g : Am trying to understand when this would or would n't happen - e.g . it does n't happen for these cases : It seems the compiler is n't smart enough to detect when the if condition is constantly true - could someon... | Why is n't unreachable code detected when an if condition is a constant ? |
Java : I have the following code and I got following output in consoleWhy does n't this call test ( Object a ) ? Can you some one explain how it took `` List as '' null ? <code> import java.util.List ; public class Sample { public static void main ( String [ ] args ) { test ( null ) ; } static void test ( List < Object... | Null value in method parameter |
Java : Say I need to store a collection of Student objects and each student has a unique id . One option is to store all of them in a list , but then when searching for a student , I 'd have to perform a linear search and check their id 's . The other option would be to use a map , of something like : Map where the key... | Correct usage of storing objects in maps |
Java : I have a piece of code that I use to generate PDF document , it 's simplified just to demonstrate the problem.I want to convert it to functional style with Java 8 streams.I know that I javascript I can use reduce like this : I am trying to use same approach in Java , so my code is something like this : But it 's... | Java 8 streams - use reduce with alternative accumulator return type |
Java : Can someone explain to me how to get the following method to return a value of false for the input shown ? It 's returning true , which is something I do n't expect.I think this should return false , but apparently Java does n't think so . The actual date string provided contains these extra characters at the en... | Why does an invalid date parses successfully as a real date ? |
Java : Synchronization works correctly in this code : Output : but not in this code : Output : I can not understand what difference wrt Synchronization does it make to initialize PrintNumbers in the Runnable MyThread and in the SyncExample class . Please explain . <code> class PrintNumbers { synchronized public void di... | Why does synchronization not work in the second code ? |
Java : Due to debugging reason most parts of the code in my application has this recurrent portion of code : Now , if the boolean values turn to false this becomes dead code . My question is if in this case the Android compiler would do basics optimizations such as constant folding and dead code remotion ? If the answe... | Are hardcoded conditions optimized by JVM in Android ? |
Java : While looking at the Java invokedynamic documentation , I saw the following example of a Java feature called `` exotic identifiers '' : I was unable to get this to work on an openjdk8 on my machine . Further googling found a few bug reports relating to this feature but not much else . Specifically this bug , and... | Status of Java exotic identifiers |
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