如何为Java提供Scala随播对象的类? [英] How can I provide a scala companion object's class to Java?

问题描述

我有一个Java代码，用于在类的静态方法中查找注释.

I have a Java code that looks for annotations in static methods of a class.

processor.readStatics( MyClass.class );  // Takes Class<?>

如何从scala中向此函数提供scala伴侣对象的方法?

How can I provide the methods of a scala companion object to this function from within scala?

class MyClass {
}
object MyClass {
  def hello() { println("Hello (object)") } 
}

我似乎是:

MyClass$.MODULE$.getClass()

应该是 answer .但是，scala中似乎缺少MyClass $(至少在2.10中)，并且仅对Java可见.

should be the answer. However, MyClass$ seems to be missing from scala (in 2.10, at least) and only visible to Java.

println( Class.forName("MyClass$.MODULE$") )

也失败了.

推荐答案

类名称为MyClass$(并带有适当的程序包名称).

Class name is MyClass$ (with the appropriate package name prepended).

println(Class.forName("MyClass$"))将打印出"Class MyClass $".

println(Class.forName("MyClass$")) will print out "class MyClass$".

MyClass$.MODULE$是类的 instance ，引用单例对象.

MyClass$.MODULE$ is the instance of the class, referencing the singleton object.

println(MyClass$.MODULE$ == MyClass)仍会打印出"true"，即使在编译时，您也会收到一条警告，指出该比较总是产生false:)

println(MyClass$.MODULE$ == MyClass) will print out "true" even though, when compiling, you will get a warning that this comparison always yields false :)

请注意，由于某种原因，这些都不能在repl中起作用.您实际上需要创建一个.scala文件，使用scalac进行编译，然后运行.

Note, that none of this works in repl for some reason. You need to actually create a .scala file, compile it with scalac, and run.

因此，在Java中，使用MyClass$静态引用MyClass对象的类，使用MyClass$.MODULE$引用MyClass对象的单例实例，使用MyClass$.class或MyClass$.MODULE$.getClass()引用该类的动态对象，使用Class.forName("MyClass$")在运行时按名称访问它.

So, in java, use MyClass$ to reference the class of MyClass object statically, use MyClass$.MODULE$ to reference the singleton instance of MyClass object, use MyClass$.class or MyClass$.MODULE$.getClass() to reference the class of the singleton object dynamically, use Class.forName("MyClass$") to access it at runtime by name.

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