java - 从 Scala 调用名为 "clone"的 Java 方法

Question

我想从 Scala 中使用以下 API 调用 Java 方法:

// Java API
public interface JavaAPI {
  JustSomeAPISpecificType clone();
}

// Scala code in class a.b.c.D
val api: JavaAPI = factory.getAPI
val result: JustSomeAPISpecificType = api.clone

但是，这不起作用，因为 Scala 编译器(2.10)认为我想调用 Object.clone:

Error: method clone in class Object cannot be accessed in Option[JavaAPI] Access to protected method clone not permitted because prefix type Option[JavaAPI] does not conform to class D in package a.b.c where the access take place

有什么想法吗？ 谢谢。

Answer 1

首先看Object#clone() signature

protected Object clone()
                throws CloneNotSupportedException

您想要重写此方法。

在您的示例中，现在您有两种方法:

protected Object clone()
                    throws CloneNotSupportedException

public JustSomeAPISpecificType clone()

参见:

JustSomeAPISpecificType.java

public enum JustSomeAPISpecificType{
INSTANCE
}

工厂.java

public class Factory {

        public static class JavaApiImpl implements JavaAPI{

                public JustSomeAPISpecificType clone(){
                        return JustSomeAPISpecificType.INSTANCE;
                }
        }

        public static JavaAPI getAPI(){
                return new JavaApiImpl();
        }
}

现在将您的文件添加到 src/main/java 并从 root 运行 sbt console:

scala> val api = Factory.getAPI
api: JavaAPI = Factory$JavaApiImpl@4243eb68

scala> api.getClass.getMethods.filter(m => m.getName.startsWith("clone")).mkString("\n")
res0: String = 
public JustSomeAPISpecificType Factory$JavaApiImpl.clone()
public java.lang.Object Factory$JavaApiImpl.clone() throws java.lang.CloneNotSupportedException

更新 如果你强制转换 - 你将看到方法克隆(如果工厂是公共(public)的)。

scala> api.asInstanceOf[Factory.JavaApiImpl].clone
res4: JustSomeAPISpecificType = INSTANCE