Recent questions tagged java

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java - Should you check if the map containsKey before using ConcurrentMap's putIfAbsent

I have been using Java's ConcurrentMap for a map that can be used from multiple threads. The putIfAbsent is a ... a putIfAbsent in this manner? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - When NOT to call super() method when overriding?

When I make my own Android custom class, I extend its native class. Then when I want to override the base method ... but I am really confused.) See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - implements Closeable or implements AutoCloseable

I'm in the process of learning Java and I cannot find any good explanation on the implements Closeable and the ... () throws IOException { } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - 8080 port already taken issue when trying to redeploy project from Spring Tool Suite IDE

I have strange thing when I try to modify Spring project inside my Spring Tool Suite. On the first load (deploy) ... any kind of help or info. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - The HashSet<T>.removeAll method is surprisingly slow

Jon Skeet recently raised an interesting programming topic on his blog: "There's a hole in my abstraction, dear ... >.removeAll method so slow? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - What is difference between cacerts and keystore?

What's the difference between the two, cacerts and keystore? If I use the definition found in these links, ... one of them or alternate? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - How to expand folded package chain in Intellij IDEA?

Intellij IDEA automatically chain packages together if the intermediate ones are otherwise empty. It is a nice ... are chained together. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Performance comparison of Thrift, Protocol Buffers, JSON, EJB, other?

We're looking into transport/protocol solutions and were about to do various performance tests, so I thought I'd ... into this question as well. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Should I use EJB3 or Spring for my business layer?

My team is developing a new service oriented product with a web front-end. In discussions about what ... find good benchmark information? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Ubuntu: OpenJDK 8 - Unable to locate package

So I just installed Ubuntu, and this is my first time working in a Linux environment, so bear with my ... first thing in the morning. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Room database migration if only new table is added

Let't assume, I have a simple Room database: @Database(entities = {User.class}, version = 1) abstract class ... Please create migration for me? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Colorize logs in eclipse console

Is there a way to colorize parts of logs in the eclipse console. I know I could send to error and ... presentation of the information by CSS. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - How to check if a variable exists in a FreeMarker template?

I have a Freemarker template which contains a bunch of placeholders for which values are supplied when the ... adding this extra variable. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Set drawable size programmatically

The images (icons) come in roughly the same size, but I need to resize them in order for the buttons to remain ... (drawable, null, null, null); See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Class Not Found Exception when running JUnit test

I am getting this error when running JUnit test in Eclipse: Class not found com.myproject.server.MyTest java. ... still getting the same error. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Unable to find a @SpringBootConfiguration when doing a JpaTest

I'm new to frameworks (just passed the class) and this is my first time using Spring Boot. I'm trying ... findByUsername(String username); } } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - The fundamentals of Hash tables?

I'm quite confused about the basic concepts of a Hash table. If I were to code a hash how would I even ... be appreciated as a learning tool... See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - When should I choose SAX over StAX?

Streaming xml-parsers like SAX and StAX are faster and more memory efficient than parsers building a tree-structure ... SAX instead of StAX? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Using multiple property files (via PropertyPlaceholderConfigurer) in multiple projects/modules

We are currently writing an application which is split into multiple projects/modules. For example, let's ... the stackoverflow community.. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Observable vs Flowable rxJava2

I have been looking at new rx java 2 and I'm not quite sure I understand the idea of backpressure ... managing and handling the consuming? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Why so red? IntelliJ seems to think every declaration/method cannot be found/resolved

I just installed and re-installed IntelliJ. Every Java file is coming up RED. I checked the JDK; it is at 1. ... do I fix these false errors? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Using NotNull Annotation in method argument

I just started using the @NotNull annotation with Java 8 and getting some unexpected results. I have a method ... would be greatly appreciated. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Parametric polymorphism vs Ad-hoc polymorphism

I would like to understand the key difference between parametric polymorphism such as polymorphism of generic classes/ ... Thanks in advance. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - What is the purpose of JNDI

How can you realize the usage of JNDI , with an example if possible? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Servlet-3 Async Context, how to do asynchronous writes?

Problem Description Servlet-3.0 API allows to detach a request/response context and answer to it later. ... be implemented without blocking? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Best practices/performance: mixing StringBuilder.append with String.concat

I'm trying to understand what the best practice is and why for concatenating string literals and variables for different ... just not be used? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Difference between servlet and web service

What is the difference between these 2? I found few results on google nothing conclusive. Here is a follow up ... or servlet or something else ? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - What are detached, persistent and transient objects in hibernate?

What are detached, persistent and transient objects in hibernate? Please explain with an example. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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