To initialize my logger apparently I need:
val LOGGER : Logger = LoggerFactory.getLogger(Foo::class.java);
如果我这么做了:
val LOGGER : Logger = LoggerFactory.getLogger(Foo::javaClass);
It complains that the parameter type is not compatible with getLogger. However according to the API, both are Class<Foo>. How are they different?
javaClass是一个扩展属性，返回实例化object的runtime Java class.在您的例子中，它被用作属性引用，这将为您提供一个KProperty1<Foo, Class<Foo>>，表示扩展函数本身:
val T.javaClass: java.lang.Class<T>
You could use this in combination with a receiver, e.g. if Foo provided a default constructor you could say:
Foo::javaClass.get(Foo())
可简化为:
Foo().javaClass
Using ::class.java on the other hand, gives you the Java Class<?> as described in "class references" directly. All three possibilities in a simple example:
val kProperty1: KProperty1<Foo, Class<Foo>> = Foo::javaClass
kProperty1.get(Foo()) //class de.swirtz.kotlin.misc.Foo
Foo::class.java //class de.swirtz.kotlin.misc.Foo
Foo().javaClass //class de.swirtz.kotlin.misc.Foo