Java
-
Java – null pointer exception error, no obvious code error
I have a mistake here. I don't know where it comes from My java course for beginners is high school, so I don't have m…… -
Multithreading – aborts the entire application from a thread in Delphi
There is a major problem with my Delphi app I'm developing a software that uses external security I am using a USB dev…… -
If Java returns NoSuchElementException
How to create an IF statement to check whether the function returns "NoSuchElementException"? Similar to what I have b…… -
Java – what exactly is system out？
I've noticed that system. Net has never been initialized through a jar file launched from the command line (that is, t…… -
JavaFX scrollpane – check the displayed components
I want to know if there is a scrollpane attribute in JavaFX 8 that can be used to listen for components currently disp…… -
Java-8 – building Maven assemblies in Java 8
I changed the Java version used in my project Now I'm using Lambdas expressions If I compile IDE (IntelliJ), it works …… -
Is it possible to resolve ambiguity through annotations in Java
See English answers > method overloading for null argument 7 void bla(Integer a); void bla(String a); Basically, wh…… -
JavaFX: creating custom data attributes for nodes
I currently need custom attributes, which I can get at any time Is there any way to create custom data attributes for …… -
Java generics – differences between method declarations
What is the difference between the following two method declarations: 1. <R> Stream<R> myFunc(Function<…… -
How do I start three tasks that will run sequentially in Java?
I'm trying to start three tasks: the first one will read some emails, generate some charts based on these emails after…… -
Multithreading – threads and event loops in QT applications
Anyone can explain the differences between threads and event loops and how to use it in QT applications Where can I us…… -
NoClassDefFoundError: org / Apache / POI / SS / formula / UDF / UDF finder error in Java
Hi, I'm using Apache POI to write an excel I am using sxssfworkbook But when this code is executed, I get this error a…… -
How do I display tabs with spaces?
I have a java program that draws each character (in its own frame) from a text file on a JPanel with a grid Code of dr…… -
Java – SQS expiredtoken: the security token contained in the request is expired status code: 403
I have a long - running worker process running on EC2 that uses items from the SQS queue After some time (8-12 hours, …… -
How to convert a list into a map in Java 8 Map function in chain
See the English answer > java 8 grouping using custom collector? 3 class Passenger { String type; String firs…… -
Java – limit cells to values in Apache POI only
We are using the Apache POI library to create excel worksheets How do we restrict cells to accept only numeric values?…… -
Java-8 – you can know the size of the stream without using terminal operations
I have three interfaces public interface IGhOrg { int getId(); String getLogin(); String getName(); …… -
How to use gridpane JavaFX to make buttons span multiple columns / rows?
I am new to JavaFX and am trying to use gridpane for simple button design I can't figure out how to make buttons span …… -
Java – use mockmvc to get the HttpServletRequest attribute
I have a very simple controller defined in this way: @RequestMapping(value = "/api/test",method = RequestMethod.GET,pr…… -
How can I avoid doing a lot of if in Java?
In C, I will use the mapping of int / pointer to implement such a function: @ h_ 404_ 7@ std::map = { {Code::Value1,Ha…… -
Java – if value is empty, delete the key
Suppose we have a map < key, collection < value > > mymap and a method to delete values from the collectio…… -
java – Thread. Yield () is still a cross platform minefield?
I can find the answers of old references and so, say thread The behavior of yield() varies from platform to platform T…… -
Java – unit testing: calling @PostConstruct after defining simulation behavior
I have two classes: public MyService { @Autowired private MyDao myDao; private List<Items>…… -
JavaDocs throws illegalargumentexception
I am using IntelliJ idea. When I start generating JavaDocs (through tools - > generate Javadoc), I will throw an il…… -
Java streams – how to use conditions on keys to translate all values in a collection map
I have a map Let's talk Map<Long,List<MyObj>> I want to create a long array in all myobjs, where the key (…… -
Convert Map > > to list using java 8
I'm trying to convert map < string, navigablemap < long, collection < string > > into list < string …… -
Java –: the selected pseudo class style does not apply to cells
I have some tableviews in the scene. I want to highlight the selected cells According to JavaFX CSS reference, there i…… -
Java – how to allow users to select classes to initialize
I have an abstract class foo, which contains a function a (object o) I hope the users of the program can determine the…… -
If the file does not exist, what will readalllines return?
The Oracle document says here, files The readalllines (path, charset CS) method returns the lines in the file as list …… -
Java – how do you ensure that spring @ EventListener is called first?
When implementing the applicationlister interface, there is an option to implement ordered to specify the call order S…… -
Java – localdate cannot resolve ‘WW’ using ‘yyyy’
I must parse the date in the following format: "201710", in which the year number of 10 weeks I try to achieve it in t…… -
Java – foreach function does not work in spark dataframe
According to the dataframes API, the definition is: public void foreach(scala.Function1<Row,scala.runtime.@R_841_24……