Java
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Java ThreadLocal singleton – what is it?
Laymen say, what does it mean when someone says that an object is a thread singleton in Java? I'm attending a lecture …… -
java – Arrays. Contains (int) error
May I ask why the following output is false? import java.util.Arrays; public class Test2 { public static void m…… -
Java – creating CDATA sections is confusing
I tried to create a CDATA section in the description field, but failed The code is very simple, but there is no CDATA …… -
Java – why does the execution order between printstacktrace () and other methods seem uncertain?
In the following code snippet, the printStackTrace () method is called in the catch block. After running the program, …… -
Java – PowerManager on Android devices WakeLock
I want to implement a wakelock in my Android application I have the following code in oncreat(): pm = (PowerManager) g…… -
Initializes a Java object instance that contains an array of objects
The following code is correct: public Sample mOboeSamples[] = { new Sample(1,1),new Sample(1,2) }; public Sample mGuit…… -
Java – declare int [] array without defining size?
This is my code: int[] primes = new int[25]; for (int i = 2; i <= 100; i++) { for (int j = i; j &g…… -
Is java – x Lang safe?
I often hear this question in discussions with Java developers They (Java developers) always ask if your choice is sec…… -
Java – helps create generic classes to avoid code duplication
I have a simple question. Try to use appengine to keep dry The following two functions are the same except for the obj…… -
Java – when using Grails sortedset, the first () element cannot be accessed from an empty list
I'm trying to dynamically create some Grails domain objects and then add a sortedset declared in another Grails domain…… -
Java – what are JPanel, JFrame, jlayeredpane and jrootpane
I am a novice in Java. When reading, I encountered various frameworks and panels. What is the confusion between JFrame…… -
Java – NullPointerException when trying to read parcel ArrayList
I have a class message that implements Parcelable It contains an ArrayList, and attachmentsdata is also one of my clas…… -
Java – why link string Will trim () throw an exception?
Sorry, if this is a stupid question, but I can't find an explanation I have a string like this: String str ="This is 5…… -
JavaFX – how to add a container in the anchor pane
I have a simple project that contains fxml. XML with a splitter So fxml is like this: <AnchorPane id="AnchorPane" p…… -
Java – how many elements does ArrayList add when it resizes itself?
Java's ArrayList dynamically extends itself when needed How many elements will it add when the extension occurs? Does …… -
Java – breaks a string into two at a hyphen
I get the string variable from the request String issueField = request.getParameter("issueno"); This may or may not ha…… -
java – Codingbat- Recursion1- count7
Anyone can program the next question for me (from codingbat – recursion1 – count7) Given a nonnegative int n, the numb…… -
Java – under what circumstances thread Is sleep () the best way to pause a thread?
Thread. Sleep () seems like a very useless concept to me, because the only way I see it work is in the following scena…… -
Override the list result type in Java
I want to compile some variations of this code in Java class X { List<X> getvalue(){...}; } class Y extends…… -
Java – get the class name with generic information
In the Java serialization problem, I want to save some class names. I have some problems with generic classes Any idea…… -
Get metadata information of file owner using java
I am trying to retrieve the owner of the file using the following code: Path file = Paths.get( fileToExtract.getAbsolu…… -
Java – override generic methods using non generic implementations
I was trying generics in Java and thought of this example If I have classA < T >, I can override it with Subclas…… -
Java – VTD – XML parsing performance (key factor of speed) Request feedback / comments
I'm about to use VTD XML (in http://vtd-xml.sourceforge.net/ Found), but I'm interested in getting feedback on any act…… -
Java – how to create CSV files using servlets?
I want to download the CSV file from the servlet Data from object [] obj = search getSearch(); I have a data object []…… -
Java – when we change to bytes, why is the result – 2 when 127 * 2?
This is my code: public class test { public static void main(String[] args) { byte a=(byte)127,b=2; byt…… -
Java – rest Service on wildfly pathparam is empty
I am building a rest service using Jee 7 and deploying it on wildfly 8 With the exception of pathparam, everything see…… -
Algorithm – search for the 7th largest element in the largest heap?
So my friend and I don't agree on this issue It requires the time complexity of searching the 7th largest element in t…… -
Java monthly timer
I'm trying to create a timer / TimerTask that will run on the same day of each month I can't schedule a repeat timer b…… -
Java Concurrent HashMap
I want to convert concurrenthashmap to treemap Can I do that? Solution If you need a sorted concurrentmap, please chec…… -
Accessing subclass fields from a base class in Java
I have a base class called geometry, in which there is a subclass sphere: public class Geometry { String shape_name;…… -
Java – refresh the Android viewpager fragment on refresh
I'm new to Android. I really don't understand why the dynamically added fragment content (such as some images added af…… -
How to truncate PostgreSQL tables from JDBC
I have a PostgreSQL database. I want to truncate some tables using JDBC What do I do? This is what I've tried, but the……