Java
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Dplyr: select all variables except those contained in the vector
This should be a simple question, but I'm trying I have a variable name vector that I want to exclude from the data fr…… -
Java – warning: unclosed file of type ‘[io. Realm. Orderlistrealmproxy]’; These types are not annotated
What is wrong?! Solution This is because you are using list < > instead of realmlist < > you extend realmo…… -
Java reactor: how to generate flux from stdin?
I want to read user generated messages from stdin asynchronously Flux.from(stdinPublisher()) .subscribe(msg ->…… -
How to properly close JavaFX alerts / filechooser, etc
I am looking at this problem JavaFX show dialogue after thread task is completed, but my problem is just the opposite …… -
Java recursion does not iterate over all top-level elements
I face the problem of recursion I have an object that contains its own list. Each object in the list can save its own …… -
For loop to Java 8 stream foreach()
See English answers > break or return from Java 8 stream for each? 11 If any value does not exist, it immediately r…… -
java – Guice Bind Generic Types
Is there any way to bind the generic type of the following type: public interface A<T extends Number> { void p…… -
Java – how to short circuit when calculating duplicate values between two lists?
I have 2 lists. I need to calculate / check the duplicate elements in list a that match the elements in List B in the …… -
Java – is it possible to shallow copy singleton class objects?
Using the clone method, can we get many instances of a class that has become a singleton? In addition, is it necessary…… -
PAT A1001-A1004
A1002 ： A+B for Polynomials (25 point(s)) The key to solving this problem is the condition given by the problem: the …… -
How do I convert numbers from double to int without rounding?
I want to calculate how many columns can fit in the container First, I calculate how many columns can fit, and then ca…… -
Why do two java files that differ only in comments produce different class files?
I have one named one Java file, which has only one comment line I compile it to generate the class file one Class and …… -
Java 9’s new docs structure – where are the “old” Java packages?
I'm used to accessing Java se documents from the following links, where I can search for Java awt,java. Util and other…… -
Java – does referencing array indexes cause memory leaks?
I'm reading "item 6: eliminating obsolete object references" in the second edition of effective Java The following is …… -
Collections – java8 converts lists to map >
I have a list < person > object and want to convert it to map < integer. The keyword of the list < person …… -
Java – cannot use paths Get() loads files from Maven resources
I apologize for this seemingly simple and almost stupid problem, but I spent a lot of time fixing it without much succ…… -
Java – convert the 3D world (arcore anchor / pose) to the corresponding 2D screen coordinates
I am trying to achieve this transformation Given the anchor pose in arcore, how can the corresponding 2D coordinates b…… -
Java 8 groupby one field and then maps to multiple fields
I have an object structure like this class Person{ String userId; String firstName; String lastName; Set&l…… -
Design pattern course design pattern intensive lecture 7-3 source code analysis of builder pattern (JDK + guava + Spring + mybaties)
StringBuilder public synchronized StringBuffer append(Object obj) { super.append(String.valueOf(obj)); return this…… -
How to assign incremental values to lists in Java 8
Suppose you have a list of objects The list is sorted by one or more fields of the object So according to the sort lis…… -
Java datetimeformatterbuilder with optional mode causes datetimeparseexception
target Provide a flexible parser for localdate instances, which can process input in one of the following formats: >…… -
Java – is it more efficient to scan an array once for multiple predicates or multiple times for a single predicate
I have an int array of 1000 elements I need to extract the sizes of various subgroups in the array (how many are even,…… -
Differences between Java 6 and Java 7 in ArrayList capacity growth
I have a question about how to manage the capacity growth (not size, but capacity) of ArrayList in Java At this time, …… -
Java – when calling integer Should you check whether a string is empty before parseInt?
In a loop, thousands of items are converted from string to int, calling integer Should you check whether the string is…… -
Java – why doesn’t the Oracle specification tell you anything about meta spaces?
As we all know, Java 1.8 permgen was deleted and replaced by Metaspace I've read a lot about Metaspace, and I'm sure i…… -
There was a problem using Jackson to use JSON serialization in Java
Good morning, man! I have a JSON string that looks like: { "StatusCode":0,"Message":null,"ExecutionTime":0,"Respons…… -
Java – thread safety when inserting values into HashMap in a parallel stream
I need to make an asynchronous call with a timeout of 10 seconds, and I need to do this for each element in the map Th…… -
Lambda – grouping and summing list items using java 8 streams
Suppose I have a list < banana > banana Banana class is defined as follows: Banana. java public class Banana{ …… -
Java – what’s the difference between formatting integers as% D and% s?
Although both are grammatically valid, the following important potential differences should be noted: String result = …… -
Java – duplicate fields in JSON response
I used spring boot Jackson dependency and Lombok in my project. In response, I got duplicate fields because of undersc…… -
Java – what is the best mode or method to load a static cache?
Suppose I have the following (assuming only Java 1.4, so there is no generics): public class CacheManager { static…… -
Migration issues from JUnit 4 to JUnit 5
I'm migrating my code base from junit4 to junit5 I used mockito in my testcase Below is the different version I use fo……