Recent questions tagged java

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java - Why does int i = 1024 * 1024 * 1024 * 1024 compile without error?

The limit of int is from -2147483648 to 2147483647. If I input int i = 2147483648; then Eclipse will ... second variant produces no error. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Why does the Sun JVM continue to consume ever more RSS memory even when the heap, etc sizes are stable?

Over the past year I've made huge improvements in my application's Java heap usage--a solid 66% reduction. ... of the application load metrics. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Inspect in memory hsqldb while debugging

We're using hdsqldb in memory to run junit tests which operate against a database. The db is setup before ... Any help is highly appreciated! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Logging error to stderr and debug, info to stdout with log4j

I want to add logging to an application I am developing, using apache log4j. At this point I want to redirect ... . is printed at stdout too. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Why project Jigsaw / JPMS?

Java's package management system always seemed simple and effective to me. It is heavily used by the JDK itself. We ... itself and to the JDK. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Why does this method print 4?

I was wondering what happens when you try to catch an StackOverflowError and came up with the following method: ... else on other systems. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Why are composite keys discouraged in hibernate?

This is from Hibernate official tutorial: There is an alternative <composite-id> declaration that allows access to ... s the better alternative? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - How to create custom annotation with code behind

I would like to create my own custom annotation. My framework is Stand alone java application. When someone annotate ... sample i Wrote below). See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - What is the difference between log4j, slf4j and logback?

I am little bit confused by these three logger libraries. It seems like that they can do the similar thing in java logging... See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Difference between size and length methods?

What is the difference between .size() and .length ? Is .size() only for arraylists and .length only for arrays? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - How do you create a Spring MVC project in Eclipse?

I am trying to follow the basic tutorial for Spring MVC but got lost at creating a new project in Eclipse. ... up Eclipse would be appreciated. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Member variables vs setArguments in Fragments

I've noticed that in the Android reference for Fragments (notably DialogFragment) that they do a couple of things ... an overhead. Any thoughts? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - How to query data out of the box using Spring data JPA by both Sort and Pageable?

I am trying Spring data JPA in my project. I want to know if there is an out-of-the-box API to query ... Pageable pageable), so I am curious. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - What GUI libraries are the JetBrains using?

Background I am somewhat new to Java and am enjoying using IntelliJ IDE developed by the JetBrains team. I have ... this is used by IntelliJ. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - CompletableFuture<T> class: join() vs get()

What is the difference between the get() and join() methods of the CompletableFuture<T> class? Below is the my ... see no difference in result. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Create a directory if it does not exist and then create the files in that directory as well

The condition is if the directory exists it has to create files in that specific directory without creating a new ... value); bw.close(); See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - How do I retrieve query parameters in a Spring Boot controller?

I am developing a project using Spring Boot. I've a controller which accepts GET requests. Currently I'm accepting ... getPrice(); return i; } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Difference between the annotations @GetMapping and @RequestMapping(method = RequestMethod.GET)

What's the difference between @GetMapping and @RequestMapping(method = RequestMethod.GET)? I've seen in some ... used instead of @RequestMapping See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - How does the Garbage-First Garbage Collector work?

Can someone explain how the G1 Garbage Collector works please? I haven't been able to find any ... descriptions anywhere yet. Thanks See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Generate war file from tomcat webapp folder

I have a tomcat server working, and there I have a webapp folder my_web_app. I didn't deploy the project; I ... a .war file from this webapp? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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480 views

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java - What is the difference between @ManyToOne(optional=false) vs. @Column(nullable=false)

In JPA, I am confused when to use the attribute optional=false and the annotation @Column(nullable=false). What is the difference? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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217 views

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java - initializing a Guava ImmutableMap

Guava offers a nice shortcut for initializing a map. However I get the following compiler error (Eclipse Indigo) ... tell me what is missing? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - How to get the name of a class without the package?

In C# we have Type.FullName and Type.Name for getting the name of a type (class in this case) with or ... it of the package name manually. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Hibernate Many to Many Relations Set Or List?

I have a many to many relationship at my Java beans. When I use List to define my variables as like: ... about performance and other issues)? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - Heap vs Stack vs Perm Space

What are the differences between the Java memory spaces (Perm Space, Space Stack, Heap Space)? When does the ... /etc., are there differences? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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205 views

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java - Does a finally block run even if you throw a new Exception?

In this code will someVar be set even if the catch block is executed and the second Exception is thrown? public ... this.someVar= true; } } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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230 views

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java - Why explicitly throw a NullPointerException rather than letting it happen naturally?

When reading JDK source code, I find it common that the author will check the parameters if they are null and then ... true); } return null; } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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java - What does "implements" do on a class?

If a class implements another class... what does that mean? I found this code sample: http://www.java2s.com/ ... have any explanation with it... See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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