Java
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Java – find unpaired numbers in an array
I have an array that repeats all elements except one: int[] a={2,6,2,4,1,4}; How do I find unpaired element integers? …… -
IO stream technology
Create and delete files: createnewfile(), delete() Create folders: mkdir() and mkdirs() List next level: lists the sub…… -
How to resolve file names in Java?
I have a java file path /opt/test/myfolder/myinsidefolder/myfile. jar I want to replace the file path with the root pa…… -
Java – how to add padding using container?
I tried to do some padding at the top, but how do I use the container? JFrame frame = super.screen.getFullScreenWindow…… -
How to use Qt5 to realize multithreading (I)
#include "thread_one.h" thread_one::thread_one(QObject *parent) : QThread(parent) { } void thread_one::run() { …… -
The value of Java jsonobject array is key
I'm new to Java, so it's a little confusing I want to get a string in JSON format What I want is { "user": [ "name","l…… -
Java hashcode() string conflict
I know little about hash codes I found that this code can print out collisions Can you tell me what collision is and h…… -
Java – allocate memory using thread
I wonder what happens if a local thread is declared in a method? Usually, after the function returns, all local variab…… -
How to solve this Java lang.ClassCastException：org. apache. tomcat. dbcp. dbcp. Basicdatasource cannot be cast to org apache. tomcat. jdbc. pool. DataSource？
I tried to use pool for database connection in Tomcat. This is my context: <Resource name="jdbc/slingemp" auth="Con…… -
Java – the difference between classes and packages
What is the difference between classes and packages in Java? Solution Class is a declaration (usually an implementatio…… -
java – Integer. Parseint() does not resolve large negative numbers
When I try integer Why is numberformatexception thrown when parseInt ("80000010", 16)? This is a 32 - bit number, whic…… -
Java – Android replaces multiple characters from a string
I know it may be an amateur problem, but for some reason, I don't remember how to do it String s ="["; String q ="]"; …… -
Is the result of mathematical operation on Java – double completely repeatable?
I have a complex data processing algorithm, using java 8 and double as the data type Given the same input (hundreds of…… -
Java — on doubles and equality
I have a method that returns a double When I tested this method as part of JUnit, I noticed the following oddities: St…… -
Java – is an if else tree the best approach in the following situations?
What am I doing: I'm creating a simple calculator in Java that reads a string written in postfix notation (for example…… -
Thread problem in Java HashMap
Something happened that I'm not sure should work Obviously it's because I've seen it, but I need to find the root caus…… -
Java – a naming convention for variables that work like constants
I have a variable that I'm using like a constant (it never changes) I cannot declare it as a constant because the valu…… -
Where can I find Java main functions
Is public static void main (string [] args) a built-in or user-defined or overridden function of some classes provided…… -
Java – how to avoid instanceof calls?
I defined this simple method: public static boolean isBorder(int x,int y) throws CollisionDetectionException { …… -
Java – what is system in
Consider this scanner input example Scanner user_input = new Scanner( system.in ); The scanner is class user_ Input is…… -
Java string Split() deletes trailing empty entries
I'm trying to parse some pipe delimited records I have this Code: public class Test { public static void main(Stri…… -
Inconsistent Java performance
I have an interpreter written in Java I tried to test the performance results of various optimizations in the interpre…… -
Can Java 10 compiled classes run on 9?
See the English answer > can Java 8 code be compiled to run on Java 7 JVM? 5 Is my hypothesis correct? Solution Thi…… -
How to use file. XML in Java Mkdirs () writes elegant code?
I need a directory to save the file, but I'm not sure if it exists File saveDir = new File("/tmp/appname/savedir/"); i…… -
How do I embed java code in JSF pages?
I have: In this JSF page, I have a login form Inside the managebean, I have a logincheck function public void loginChe…… -
Java – optimal solution of maximum single sales profit algorithm
The input array is: A[0] = 23171 A[1] = 21015 A[2] = 21123 A[3] = 21366 A[4] = 21013 A[5] = 21367 The mission is t…… -
Java generic problem
Can I write a method that can create an instance of any specified type? I think Java generics should help, so it might…… -
Java 8 avoids a large number of if / else statements
I have something that looks like this: public boolean isValidObject(SomeObject obj){ if(obj.getField() == null){ …… -
Use AutoCAD Library in Java to read DWG file?
Are there any open source Java or JavaScript libraries available for parsing DWG file and get objects from it I want t…… -
Java for loop problem
I'm making a java program to calculate Simpson's integral rules This is my code Note the second column of numbers in t…… -
C command line strings like Java?
Is there any way to get the C string from the command line, just like in Java? public static void main(String[] args) …… -
Deprecated in Java 1.6
In Java 1.5, to discard a method, you will: @Deprecated int foo(int bar) { } Compiling in Java 1.6 results in the foll……