如何从 Java 调用具体的 Scala 特征方法? [英] How to invoke a concrete Scala trait method from Java?

问题描述

我有一个 Java/Scala 混合 Maven 项目.我需要重用 Saddle 方法 make，该方法具体定义为名为 Index 的特征的一部分.该方法定义为 here 如果这有任何帮助.我曾尝试使用 Index.make 或 Index$class.make 从 java 调用该方法，但在这两种情况下，我都收到 error: cannot find symbol 编译错误.

I have a Java / Scala mix Maven project. I need to reuse a Saddle method make that is concretely defined as part of a trait called Index. The method is defined here if that helps in any way. I have tried calling that method from java using Index.make or Index$class.make but in both cases I get the error: cannot find symbol compilation error.

有没有办法从 Java 调用具体的 Trait 方法?

Is there a way to call a concrete Trait method from Java?

推荐答案

trait 类似于 Java 接口，它不是具体的构造函数.

A trait is similar to a Java interface in a sense that it is not a concrete constructor.

来自斯卡拉:

class IndexImpl extends Index[SomeParamtersHere] {}
val x = new ClassImpl
x.make(..)

或者使用一个对象:

object Index extends Index {}
Index.make(..)

来自 Java:

具有具体实现的特征将编译为适当的抽象类.如果某些成员没有具体的实现，你必须实现它们.

Traits with concrete implementations will compile to the appropriate abstract class. If certain members don't have concrete implementation, you have to implement them.

import org.saddle.Index
public class TraitImpl extends Index$class {
}

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