[英]How can I implement a Java interface with variadic methods in Scala?
I am implementing a Java interface containing variadic methods like so: 我正在实现一个包含可变方法的Java接口,如下所示:
interface Footastic {
void foo(Foo... args);
}
Is it possible to implement this interface in Scala? 是否可以在Scala中实现此接口? Variadic functions are handled differently in Scala, so the following won't work: 变量函数在Scala中的处理方式不同,因此以下方法不起作用:
class Awesome extends Footastic {
def foo(args: Foo*): Unit = { println("WIN"); }
// also no good: def foo(args: Array[Foo]): Unit = ...
}
Is this even possible? 这甚至可能吗?
The code you've written works as-is. 您编写的代码按原样运行。
The scala compiler will generate a bridge method which implements the signature as seen from Java and forwards to the Scala implementation. scala编译器将生成一个桥接方法,该方法实现从Java看到的签名并转发到Scala实现。
Here's the result of running javap -c on your class Awesome exactly as you wrote it, 这是在你的类上运行javap -c的结果,就像你写的那样,
public class Awesome implements Footastic,scala.ScalaObject {
public void foo(scala.collection.Seq<Foo>);
Code:
0: getstatic #11 // Field scala/Predef$.MODULE$:Lscala/Predef$;
3: ldc #14 // String WIN
5: invokevirtual #18 // Method scala/Predef$.println:(Ljava/lang/Object;)V
8: return
public void foo(Foo[]);
Code:
0: aload_0
1: getstatic #11 // Field scala/Predef$.MODULE$:Lscala/Predef$;
4: aload_1
5: checkcast #28 // class "[Ljava/lang/Object;"
8: invokevirtual #32 // Method scala/Predef$.wrapRefArray:([Ljava/lang/Object;)Lscala/collection/mutable/WrappedArray;
11: invokevirtual #36 // Method foo:(Lscala/collection/Seq;)V
14: return
public Awesome();
Code:
0: aload_0
1: invokespecial #43 // Method java/lang/Object."<init>":()V
4: return
}
The first foo method with with Seq<Foo> argument corresponds to the Scala varargs method in Awesome. 使用Seq <Foo>参数的第一个foo方法对应于Awesome中的Scala varargs方法。 The second foo method with the Foo[] argument is the bridge method supplied by the Scala compiler. 带有Foo []参数的第二个foo方法是Scala编译器提供的桥接方法。
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