Java
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Java – check whether the object is an instance of list
I have an object that sometimes contains list < Object > I want to check it with instanceof, and if so, add some…… -
Java – JPA one-to-one relationship, where the entity may not exist
I have many to one mapping between two entities (A and B, and a B can be associated with many as). I need to be able t…… -
JNI returns the signal 7 function and tries to call Java from C
I want to make a call from C to Java I try to call a function to invert a bool value without parameters This is my C c…… -
java – Jongo vs(DBObject)JSON. parse
I try to find out the advantages of Jongo instead of simply using (dbobject) JSON Parse (...) unmarshalls the JSON com…… -
Avoid nesting if else / switches – Java
I'm reviewing some code (Java) and making changes according to the business logic flowchart The current code relies on…… -
Java – store data in memory
I have "table a" in the database, which contains three columns "col 1", "col 2" and "col 3", with about 1000000 (1 mil…… -
Java – the real advantage of the factory model
I've been using the factory model for a year Sometimes I just think the real advantage is clean code Let me explain, i…… -
Java is equivalent to Matlab’s’ EPS’ or numpy / Python’s’ spacing ‘function (floating point relative precision)
background Matlab's built-in EPS function [1] can take a value x and return "the positive distance from ABS (x) to the…… -
Javaw still creates a console window; Why?
See English answer > start a java program without the console6 java -jar Jython.jar init.py However, when I change …… -
Java swing gridbaglayout panel resizing problem
I'm making a simple little swing application for a relative, but I'm having trouble animating it This is the descripti…… -
Connecting from Java to SQL server using JDBC (Windows authentication mode)
I need to use JDBC 4.0 to connect from Java to SQL Server 2008.0 Class.forName("com.microsoft.sqlserver.jdbc.sqlServer…… -
Java – an effective way to use neo4j to find a node set related to a given node
Given two nodes, is there an effective way to find a set of common nodes (with defined relationships) For example, con…… -
Java – why is it necessary to override hashcode and equals methods of HashMap?
See English answers > what issues should be considered when overriding equals and hashcode in Java? 11 Now I've rea…… -
Java dateformat: how to handle “ST”, “nd”, “Rd”, “th”?
How to use some dateformats to parse such strings? As far as I know, there is nothing in simpledateformat Solution Try…… -
In Java, is there a type constant equivalent to Pascal
In Delphi / Pascal, there is a mechanism through which local variables in a method can remember the value from one met…… -
Java – core and core_ Differences between RT and JSTL Tags
When I use <% @ taglib URI = "http: / / Java. Sun. COM / JSP / JSTL / core" prefix = "C"% > for my struts 1.3 10…… -
Using the dropwizard to process long requests
I have a simple dropwizard service. I want a rest API to start a long-running processing task - including CPU and I / …… -
Java – get interceptor parameters in struts 2
I have the following action mapping <action name="theAction" ...> ... <param name="param1">one</par…… -
Java – try creating with strings
I found an interesting case when I used a string to create and check its hash code In the first case, I use the copy c…… -
Using recursive methods in Java
For homework, I was asked to write an inclusion method for the custom linked list public class OrderedList { private …… -
Java – a technique for extending classes using private constructors
Is there a standard technique to "extend" classes with private constructors, like most singleton classes? Specifically…… -
Java – error: importing com google. appengine. api. Datastore failed to parse JPA gae GWT
Error in development mode [ERROR] [cbd] - Line 15: The import com.google.appengine.api.datastore cannot be resolved Us…… -
Java – the best way to pass objects between classes in different threads?
I have a "runnable" class "a" and I use Java unmarshallers to create new objects The maingui thread attempts to access…… -
Java – read data files into object arrays?
I encountered a problem reading files into an array of objects I created an IF statement to divide the data rows into …… -
Java – streaming video using xuggler
I can successfully play the video with xuggler using the following code I need to be able to stream from InputStream i…… -
Unexpected token using lower bound wildcard (Java)
I have something similar: interface Foo<T> { //... lines [0,45]... /*line 46*/ <R,X super T&R> Li…… -
Java try / catch problem
I'm new to Java. I always encounter problems with the try / catch function in the code, so I wonder if you can help me…… -
Java – use try catch finally to return the type
See English answers > java's return value in try catch finally mechanism4 private Integer getnumber() { Integer…… -
Java – what is the best practice for socket programming – do I turn it off or leave it open every time?
I haven't found a definite answer yet I have a client / server application in Java 7 The server and client are on sepa…… -
Click the selenium Java button
I have a button: <input type="button" onclick="onOpenSessionClick()" value="Open device access"> But when I exec…… -
Java – filechannel ByteBuffer and hashing files
I built a file hash method in Java, which accepts the input string representation of file path and file name, and then…… -
How to determine if another process is using the file (Java)
I tried many examples, but no one worked I also try to use trylock() It always returns false Why? private boolean chec……