Java
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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 = …… -
ColdFusion Java method exception not found
This question makes me very angry I'm trying to use java to create document objects in ColdFusion When I do this: nd =…… -
What is the difference between selenium standalone server and Java selenium jar files
This may sound like a stupid question, but I want to know the difference between selenium stand-alone server and Java …… -
Java – use the stream API to create an object initialization loop
I have a set of constant values that can be used as a list Using these values, I must create a key - value pair object…… -
pthread_ cond_ Which thread will signal?
When a thread calls pthread_ cond_ Signal(), unix network programming says pthread_ cond_ Signal () is just that nofit…… -
Java – sort elements by field
I have a set of objects from the same class, and each object has an enum field, which is comparable Collections.sort(A…… -
Java – ApplicationContext cannot be loaded when running spring launch integration test
I'm trying to write integration tests for spring boot I hope the server should start during the test so that I can con…… -
Java – two spring service beans with the same class name (different packages) will throw an error even if they use a qualifier
I have the following package package1; @Service @Qualifier("kb") public class UserService { ... } package package2; …… -
Why does the Java stack trace only return failures in the finally block?
I have written some automated tests, and the syntax i use is as follows – try { // Test case steps and validations…… -
Trying to understand class inheritance in Java
Let me say I have a super class public class SuperSub { public void overideThisMethod(){ System.out.println("Pri…… -
Nanosecond time in Java, do not use Java util. Date
I need as little garbage collection (GC) as possible, very accurate and accurate time, ideally once a day System. Curr…… -
Java – spring sleuth and Zipkin: artifact IO not found zipkin. brave：brave-bom：pom：4.16. 3-SNAPSHOT
I have a spring boot 2.0 0 rest service, I tried to ask sleuth and Zipkin to send the trace to my localhost Zipkin ser…… -
How to print this digital table to the console in Java?
A natural number n is required. I want to print to the console in this format: 1 2 1 3 2 1 …… -
Java – run runnable multiple times in completable future
I want to execute multiple threads, which will try to add to my custom list mylist at the same time, but I can't see a…… -
Java connection pool without JNDI?
I have a connection pool to access MySQL database from servlet I use JNDI to get the data source. JNDI is in my meta-i……