Java
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Java – polymorphism using Jackson to add subtype information at run time
I'm using Jackson to ungroup polymorphic types from JSON I use @ jsontypeinfo, @ jsonsubtypes and @ jsontypename annot…… -
Java – why can’t Tomcat find smtptransport (session, urlname)?
We have a web application that sends mail For some reason, its installation has decided that it cannot find the constr…… -
Java – multiple enumerations and one enum
When I stumbled upon something I didn't understand why, I was looking at the example implementation of publisher (asyn…… -
java – arrayListName. What does sort (null) do?
I have a project. The professor gave us some code There is a line in the code that puzzles me: arrayListName.sort(null…… -
Java – call thread What is the performance cost of isinterrupted()?
From the Java source code, it looks like native code Is the cost roughly equivalent to volatile reads or does it need …… -
Generic Dao in Java
I'm trying to develop a general Dao in Java I tried the following This is public abstract class AbstractDAO<T> …… -
Java – how to configure multipartresolver with different maxuploadsize for ordinary users and administrators?
I can use a 10k (10000 byte) maxuploadsize to define such a multipartresolver: <bean id="multipartResolver" cla…… -
Java scripting language (JSR 223)
I'm designing a framework. I want to attach it to the scripting language API to make it more general and easier to use…… -
Java – is it necessary to close the I / O stream created from the socket IO stream when the socket is closed?
private val in = new BufferedReader(new InputStreamReader(con.getInputStream())) private val in = new BufferedReader(n…… -
Java – abstract classes used in static blocks
I can add the abstract keyword in the static initialization block, but I cannot add abstract methods abstract void dra…… -
A Java man asked: why should I learn Python?
This may be a language troll or failure to perform basic Google search; Please rest assured that this is not the forme…… -
JUnit – integration testing of spring boot based microservices
I have read a lot of guides about using spring boot and restful services, many of which contain information about runn…… -
Java – hibernate 5: generator class = “sequence” does not work properly
I have the following mappings: <id name="id" type="java.lang.Long" column="id"> <generator class="seq…… -
Java 9 repl for running applications
Java 9 introduced repl. Exe called jshell in the JDK distribution Is there any way to connect to the jshell of the JDK…… -
Criteria – multiple expressions in the JPA querybuilder where clause do not work
I'm using javax persistence. criteria. Criteriabuilder encountered a problem creating the query I am using eclipse lin…… -
Java – iterator of wildcard type variables with upper bound
Hello, I'm trying to extend HashMap < string, string > to enforce the "all lowercase" rule public class HttpQuer…… -
How to convert vectors in 1 row table in R
In R, I have a 1 - row table How do I convert it to a vector? Specifically, the table is as follows: 0 1 2 3 4 21…… -
Nutch: using java calls instead of the command line?
Am I thick or really unable to programmatically call Apache nutch through some java code? Where are the documents (or …… -
How to use java8 lambda expressions to throw exceptions for custom checks?
See English answers > java 8: lambda streams, filter by method with exception 13 private static void readStreamWith…… -
Java – create only one object for the class and reuse the same object
I want to create only one object of a class and reuse the same object over and over again How can I do this? Solution …… -
Java – change fonts of different lines in jtextarea
I want to add different font lines in jtextarea, but the last font seems to overwrite another font Please help import …… -
Java – Jenkins build fails with svnexception
I'm trying to run Jenkins build Here is my configuration Jenkins version: 1.445 deployment: as war Java: 1.7 (server 6…… -
Java – the key in treemap returns null
So I have a very strange mistake When I first used keyset () to iterate over the first 10 keys of a large treemap, I s…… -
Java – if there is no code: is it just an intellectual challenge or is it useful?
A friend of mine is discussing these design techniques for object state transformation (he is a Java master, by the wa…… -
Java – is it valid to get the logger from the static final variable initializer?
We have many class codes, and they have some templates as follows: private static Logger logger = null; private stati…… -
Java – ActiveMQ oom with stomp enabled
After enabling the stomp protocol on the ActiveMQ server (before it only enables the default protocol), it starts to f…… -
Migrate Jersey project to work in Jersey repackaged. org. objectweb. asm. Java. In classreader Java 10 result used in lang.illegalargumentexception
Previous projects run well on Tomcat 8 and JDK 8, but when I migrate my projects on Tomcat 9 and JDK 10, it gives the …… -
Emacs – Tuareg mode and CAML mode
I am currently using Tuareg mode, but I hope to be able to use the function of cam mode In particular, I want to be ab…… -
Java – how to ignore checkstyles on methods based on specific patterns
Does the checkstyle rule methodlength have a way to set the mode for the method to be ignored? I want to disable the c…… -
Java – why should you try to throw an unchecked exception on a checked exception?
See English answers > the case against checked exceptions 32 If I have this method title, two exceptions will be th…… -
com. sun. JNA and net java. What is the difference between dev.jna?
I'm looking at the central Maven repository and looking at net java. Dev.jna and com sun. jna groupId for JNA. JNA's G…… -
Java – calculates the nth floating point number
Using 32-bit floating-point numbers, I think there are floating-point numbers like 2 ^ 31 – 1 In Java, you can use an ……