从Java使用Scala:将函数作为参数传递 [英] Using Scala from Java: passing functions as parameters

问题描述

考虑以下Scala代码:

Consider the following Scala code:

package scala_java
object MyScala {
  def setFunc(func: Int => String) {
    func(10)
  }
}

现在在Java中，我希望将MyScala用作:

Now in Java, I would have liked to use MyScala as:

package scala_java;
public class MyJava {
    public static void main(String [] args) {
        MyScala.setFunc(myFunc);  // This line gives an error
    }
    public static String myFunc(int someInt) {
        return String.valueOf(someInt);
    }
}

但是，以上方法不起作用(由于Java不允许进行函数式编程，因此无法预期).在Java中传递函数最简单的解决方法是什么?我想要一个通用解决方案，该解决方案可与具有任意数量参数的函数一起使用.

However, the above does not work (as expected since Java does not allow functional programming). What is the easiest workaround to pass a function in Java? I would like a generic solution that works with functions having arbitrary number of parameters.

Java 8的语法比下面讨论的经典解决方案好吗?

Does Java 8 have any better syntax than the classic solutions discussed below?

推荐答案

您必须在Java中手动实例化Function1.像这样:

You have to manually instantiate a Function1 in Java. Something like:

final Function1<Integer, String> f = new Function1<Integer, String>() {
    public int $tag() {
        return Function1$class.$tag(this);
    }

    public <A> Function1<A, String> compose(Function1<A, Integer> f) {
        return Function1$class.compose(this, f);
    }

    public String apply(Integer someInt) {
        return myFunc(someInt);
    }
};
MyScala.setFunc(f);

这摘自 Daniel Spiewak的"Java与Scala之间的互操作" "文章.

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