scala

Type aliasing Java classes with statics

由 亡梦爱人 提交于 2021-02-07 00:30:27
问题 Suppose MyClass is a class defined in Java, and has many static as well as non-static members. I tried to alias this class (and associated companion object) in a Scala object MyObject as shown below: object MyObject { import javastuff._ type MyAlias = MyClass val MyAlias = MyClass } Scalac complains: error: object MyClass is not a value val MyAlias = MyClass How do I work around this? Thanks. 回答1: Although this works in pure Scala for a class + companion object, it's not possible with Java's

Type aliasing Java classes with statics

由 徘徊边缘 提交于 2021-02-07 00:27:17
问题 Suppose MyClass is a class defined in Java, and has many static as well as non-static members. I tried to alias this class (and associated companion object) in a Scala object MyObject as shown below: object MyObject { import javastuff._ type MyAlias = MyClass val MyAlias = MyClass } Scalac complains: error: object MyClass is not a value val MyAlias = MyClass How do I work around this? Thanks. 回答1: Although this works in pure Scala for a class + companion object, it's not possible with Java's

Type aliasing Java classes with statics

由 大兔子大兔子 提交于 2021-02-07 00:27:06
问题 Suppose MyClass is a class defined in Java, and has many static as well as non-static members. I tried to alias this class (and associated companion object) in a Scala object MyObject as shown below: object MyObject { import javastuff._ type MyAlias = MyClass val MyAlias = MyClass } Scalac complains: error: object MyClass is not a value val MyAlias = MyClass How do I work around this? Thanks. 回答1: Although this works in pure Scala for a class + companion object, it's not possible with Java's

Type aliasing Java classes with statics

由 只愿长相守 提交于 2021-02-07 00:26:17
问题 Suppose MyClass is a class defined in Java, and has many static as well as non-static members. I tried to alias this class (and associated companion object) in a Scala object MyObject as shown below: object MyObject { import javastuff._ type MyAlias = MyClass val MyAlias = MyClass } Scalac complains: error: object MyClass is not a value val MyAlias = MyClass How do I work around this? Thanks. 回答1: Although this works in pure Scala for a class + companion object, it's not possible with Java's

Spark学习之路 （十五）SparkCore的源码解读（一）启动脚本

由 |▌冷眼眸甩不掉的悲伤 提交于 2021-02-07 00:24:44
讨论QQ：1586558083 目录 一、启动脚本分析 1.1　start-all.sh 1.2　start-master.sh 1.3　spark-config.sh(1.2的第5步) 1.4　load-spark-env.sh(1.2的第6步) 1.5　spark-env.sh 1.6　spark-daemon.sh 1.7　spark-class 1.8　start-slaves.sh 1.9　转向start-slave.sh 二、其他脚本 2.1　start-history-server.sh 2.2　start-shuffle-service.sh 2.3　start-thriftserver.sh 正文 回到顶部 一、启动脚本分析 独立部署模式下，主要由master和slaves组成，master可以利用zk实现高可用性，其driver，work，app等信息可以持久化到zk上；slaves由一台至多台主机构成。Driver通过向Master申请资源获取运行环境。 启动master和slaves主要是执行/usr/dahua/spark/sbin目录下的start-master.sh和start-slaves.sh，或者执行 start-all.sh，其中star-all.sh本质上就是调用start-master.sh和start-slaves.sh 1.1

Type aliasing Java classes with statics

由 房东的猫 提交于 2021-02-07 00:23:49
问题 Suppose MyClass is a class defined in Java, and has many static as well as non-static members. I tried to alias this class (and associated companion object) in a Scala object MyObject as shown below: object MyObject { import javastuff._ type MyAlias = MyClass val MyAlias = MyClass } Scalac complains: error: object MyClass is not a value val MyAlias = MyClass How do I work around this? Thanks. 回答1: Although this works in pure Scala for a class + companion object, it's not possible with Java's

Limiting maximum size of dataframe partition

由 梦想的初衷 提交于 2021-02-06 15:47:46
问题 When I write out a dataframe to, say, csv, a .csv file is created for each partition. Suppose I want to limit the max size of each file to, say, 1 MB. I could do the write multiple times and increase the argument to repartition each time. Is there a way I can calculate ahead of time what argument to use for repartition to ensure the max size of each file is less than some specified size. I imagine there might be pathological cases where all the data ends up on one partition. So make the

Limiting maximum size of dataframe partition

由 喜夏-厌秋 提交于 2021-02-06 15:47:41
问题 When I write out a dataframe to, say, csv, a .csv file is created for each partition. Suppose I want to limit the max size of each file to, say, 1 MB. I could do the write multiple times and increase the argument to repartition each time. Is there a way I can calculate ahead of time what argument to use for repartition to ensure the max size of each file is less than some specified size. I imagine there might be pathological cases where all the data ends up on one partition. So make the

Using future callback inside akka actor

由 匆匆过客 提交于 2021-02-06 15:31:58
问题 I've found in Akka docs: When using future callbacks, such as onComplete, onSuccess, and onFailure, inside actors you need to carefully avoid closing over the containing actor’s reference, i.e. do not call methods or access mutable state on the enclosing actor from within the callback. So does it mean that i should always use future pipeTo self and then call some functions? Or i can still use callbacks with method, then how should i avoid concurrency bugs? 回答1: It means this: class

Using future callback inside akka actor

由 試著忘記壹切 提交于 2021-02-06 15:27:25
问题 I've found in Akka docs: When using future callbacks, such as onComplete, onSuccess, and onFailure, inside actors you need to carefully avoid closing over the containing actor’s reference, i.e. do not call methods or access mutable state on the enclosing actor from within the callback. So does it mean that i should always use future pipeTo self and then call some functions? Or i can still use callbacks with method, then how should i avoid concurrency bugs? 回答1: It means this: class
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