Recent questions tagged java

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java - Spark - Group by HAVING with dataframe syntax?

What's the syntax for using a groupby-having in Spark without an sql/hiveContext? I know I can do DataFrame df = ... () does not seem to exist. 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 - multiple classes in a single file : modifier private not allowed here

I am not able to understand why this code doesn't compile: class A { public static void main(String[] args) ... the reason behind this? 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 - Initial job has not accepted any resources; check your cluster UI to ensure that workers are registered and have sufficient resources

I'm trying to run the spark examples from Eclipse and getting this generic error: Initial job has not accepted ... examples. What am I 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 - What is the significance of the POM file that Maven places in a JAR file, is it used by anything?

When Maven builds a JAR file, it places the module's POM file inside (seemingly in the directory <groupid>/< ... file it is supposed to be. 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 - Output ArrayList to String without [,] (brackets) appearing

OK, so I have an ArrayList that I need to return as a String. Right now I am using this approach: List< ... to myself in both places as needed. 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 - IllegalAccessError when using a public method reference of a package-private class through a public subclass from another package

Yesterday I faced an interesting issue after deploying my Java 8 webapp on Tomcat 8. Rather than how to ... , the IllegalAccessError is thrown? 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 - Can I access an outer class's field from a static inner class?

I have a class which has another static inner class: class A { private List<String> list; public static class B ... object for outer class } } 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 not respecting MySQL auto_increment primary key field

I am trying to learn how Hibernate works, and I am running into an almost unacceptable learning curve. I ... lasting mondo-engineered projects.) 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 - Equality between 2 HashMap

In the equals() method of my class, I am using a private instance HashMap variable to compare for the equality. ... me to a elaborate reason? 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 - Get reference to Thread Object from its ID

How can I get reference to a Running Thread if I know the ID associated with that Thread? e.g. long threadID ... I know this is totally made up 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 can I initialize an array without knowing its size?

I have a situation, where I have to apply a criteria on an input array and reuturn another array as output which ... the job in just one loop? 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 expose a method using GSon?

Using Play Framework, I serialize my models via GSON. I specify which fields are exposed and which aren't. This works great ... ) { // ... } } See Question&Answers more detail:os...

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

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462 views

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java - Why does `System.out.println(null);` give "The method println(char[]) is ambiguous for the type PrintStream error"?

I am using the code: System.out.println(null); It is showing the error: The method println(char[]) is ... Why doesn't null represent Object? See Question&Answers more detail:os...

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

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338 views

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java - JavaFX equivalent of Swing's pack()

I want to resize a window to fit the contents of the window. In Swing there is the pack() method. Is there a ... be doing, it is so basic... See Question&Answers more detail:os...

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

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254 views

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java - Can't access to files in resources directory with Maven (with Eclipse IDE)

I have a problem for a couple of hours, and I tried all the solutions I've found on tutorials. It's simple: I ... File("../test.txt") as well. See Question&Answers more detail:os...

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

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304 views

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java - Why byte b = (byte) 0xFF is equals to integer -1?

Why byte b = (byte) 0xFF is equal to integer -1? Ex: int value = byte b = (byte) 0xFF; System.out.println(value); it will print -1? 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 - JSR 310 :: System.currentTimeMillis() vs Instant.toEpochMilli() :: TimeZone

Could you please shed some light on how to obtain correct epoch time in milliseconds for a default system ... .currentTimeMillis() mention UTC? See Question&Answers more detail:os...

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

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212 views

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java - How to find if String contains html data?

How do I find if a string contains HTML data or not? The user provides input via web interface and it's ... simple text or used HTML formatting. 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 - Does JUnit support properties files for tests?

I have JUnit tests that need to run in various different staging environments. Each of the environments have ... read a .properties file? See Question&Answers more detail:os...

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

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648 views

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java - Sleep and check until condition is true

Is there a library in Java that does the following? A thread should repeatedly sleep for x milliseconds until a ... call not to fail } } See Question&Answers more detail:os...

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

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167 views

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java - how to find before and after sub-string in a string

I have a string say 123dance456 which I need to split into two strings containing the first sub-string before ... method that does just that? See Question&Answers more detail:os...

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

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791 views

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java - HTTP Status 405 - Request method 'POST' not supported (Spring MVC)

Im getting this error: HTTP Status 405 - Request method 'POST' not supported What I am trying to do is make a ... was causing the error // D See Question&Answers more detail:os...

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

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304 views

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java - How to handle order of messages in JMS?

I am reviewing a client-server application written in Java. The server receives JMS messages and processes them but ... this kind of scenario? See Question&Answers more detail:os...

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

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481 views

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java - Can Random.nextgaussian() sample values from a distribution with different mean and standard deviation?

This is a combined Java and basic math question. The documentation from Random.nextGaussian() states that it ... different mean and variance? See Question&Answers more detail:os...

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

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228 views

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java - Get number format from OS

This question seems insanely simple, yet I'm embarrased to say I haven't been able to figure out how it works. ... help. What am I doing wrong? See Question&Answers more detail:os...

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

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241 views

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java - Common HTTPclient and proxy

I am using apache's common httpclient library. Is it possible to make HTTP request over proxy? More specific ... runs fine as expected. See Question&Answers more detail:os...

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

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455 views

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java - Dynamically change JComboBox

I am fetching the data values from the database successfully. I have also stored them into a String[] ... refresh the JComboBox items. See Question&Answers more detail:os...

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

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1.0k views

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java - Required String parameter is not present error in Spring MVC

I try to make an AJAX query to my controller in Spring MVC. My action code is: @RequestMapping(value = "events/ ... text: "gfsgsdgs" userId: "1" See Question&Answers more detail:os...

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

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