java - 函数合成怎么做？

Question

在相当不耐烦地等待 Java 8 发布和阅读精彩之后 'State of the Lambda' article from Brian Goetz我注意到 function composition根本没有覆盖。

根据上述文章，在 Java 8 中应该可以实现以下功能:

// having classes Address and Person
public class Address {

    private String country;

    public String getCountry() {
        return country;
    }
}

public class Person {

    private Address address;

    public Address getAddress() {
        return address;
    }
}

// we should be able to reference their methods like
Function<Person, Address> personToAddress = Person::getAddress;
Function<Address, String> addressToCountry = Address::getCountry;

现在，如果我想将这两个函数组合成一个将 Person 映射到国家/地区的函数，我该如何在 Java 8 中实现呢？

Answer 1

有default接口(interface)函数Function::andThen和Function::compose:

Function<Person, String> toCountry = personToAddress.andThen(addressToCountry);