Java 8 如何将静态构造函数引用与三参数Java 8函数（不带make TriFunction）一起使用？

我目前正在玩Java8，发现函数有问题。我想知道是否有一种方法可以将函数引用（name:：methode）与具有树参数的函数一起使用，而不必声明新的函数接口（即TriFunction）

我试过用咖喱的方法，但没用

我有三门课：

个人类

public class Person {
    public enum Sex {
        MALE, FEMALE
    }

    private String firstName;
    private String lastName;
    private Sex gender;

    public Person(String firstName, String lastName, Sex gender) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.gender = gender;
    }

    public String getFirstName() {
        return firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public Sex getGender() {
        return gender;
    }
}

人格工厂

public class PersonFactory {
    public static Person create(String firstName, String lastName, String gender) {
        // Check firstName Parameter
        if(firstName == null || firstName.isEmpty()) {
            throw new IllegalArgumentException("The firstName argument expect to not be null or empty");
        }

        // Check lastName Parameter
        if(lastName == null || lastName.isEmpty()) {
            throw new IllegalArgumentException("The lastName argument expect to not be null or empty");
        }

        // Check gender Parameter
        if(gender == null || gender.isEmpty()) {
            throw new IllegalArgumentException("The gender argument expect to not be null or empty");
        } else {
            switch(gender) {
            case "M":
                return new Person(firstName, lastName, Sex.MALE);
            case "F":
                return new Person(firstName, lastName, Sex.FEMALE);
            default:
                throw new IllegalArgumentException("The gender parameter is supposed to be either 'M' for male or 'F' for Female");
            }
        }
    }
}

CsVPersonParser

public class CsvPersonParser {
    public Person parseLine(String line, String separator, Function<String, Function<String, Function<String, Person>>> creator) {
        String[] separedLine = line.split(separator);
        String firstName = separedLine[0];
        String lastName = separedLine[1];
        String gender = separedLine[2];
        return creator.apply(firstName).apply(lastName).apply(gender);
    }
}

编译器显示：PersonFactory类型没有定义此处适用的create（String）

---

这似乎很合乎逻辑。我没有办法。有人能帮我吗？

我想怎么做就怎么做。然而，还有两种解决方案是可能的。使用lambda而不是

PersonFactory:：create

或创建新的功能接口

结果如下：

新的功能接口

@FunctionalInterface
public interface TriFunction<A, B, C, D> {
    public D apply(A a, B b, C c);
}

public class CsvPersonParser {

    // Currying style
    public Person parseLine(String line, String separator, Function<String, Function<String, Function<String, Person>>> creator) {
        String[] separedLine = line.split(separator);
        String firstName = separedLine[0];
        String lastName = separedLine[1];
        String gender = separedLine[2];
        return creator.apply(firstName).apply(lastName).apply(gender);
    }

    // New Functionnal interface style
    public Person parseLine(String line, String separator, TriFunction<String, String, String, Person> creator) {
        String[] separedLine = line.split(separator);
        String firstName = separedLine[0];
        String lastName = separedLine[1];
        String gender = separedLine[2];
        return creator.apply(firstName, lastName, gender);
    }
}

我想知道为什么没有创造新事物就没有简单的方法

三重函数可能相当复杂。我建议你用a来创造一个人

主要原因是，您没有固定的参数排序，您可以扩展您的person。当您使用一个所有参数都是字符串的trifunction时，通常很难说哪个参数是第一个/第二个/第三个。当你想给某人添加地址时，使用诸如TriFunction这样的泛型类就变得更加困难了

我的建议是：

public interface PersonBuilder {
    PersonBuilder withFirstName(String firstName);

    PersonBuilder withLastName(String lastName);

    PersonBuilder withGender(String gender);

    Person create();
}

具体实施：

public class DefaultPersonBuilder implements PersonBuilder {

    private String firstName;
    private String lastName;
    private String gender;

    @Override
    public PersonBuilder withFirstName(String firstName) {
        this.firstName = firstName;
        return this;
    }

    @Override
    public PersonBuilder withLastName(String lastName) {
        this.lastName = lastName;
        return this;
    }

    @Override
    public PersonBuilder withGender(String gender) {
        this.gender = gender;
        return this;
    }

    @Override
    public Person create() {
        // Check firstName Parameter
        if (firstName == null || firstName.isEmpty()) {
            throw new IllegalArgumentException("The firstName argument expect to not be null or empty");
        }

        [... your implementation using the fields]
    }
}

您的解析器方法：

public Person parseLine(String line, String separator, PersonBuilder person) {
    String[] separedLine = line.split(separator);
    String firstName = separedLine[0];
    String lastName = separedLine[1];
    String gender = separedLine[2];
    return person.withFirstName(firstName).withLastName(lastName).withGender(gender).create();
}

---

现在，您可以更改参数顺序或向person添加新字段，而无需创建包含10个参数的函数。解析器接口现在也更简单了。

据我所知，这是仅有的两个选项，要么创建一个新的函数接口，要么通过

csvParser.parseLine（“blablabla”，“，”，f->l->g->PersonFactory.create（f，l，g）），将调用更改为
PersonFactory:：create
谢谢，这对我有帮助。我选择创建一个新的功能接口。它显然更具可读性。我想知道为什么不创造新的东西就没有简单的方法。非常感谢你的回答。这个设计似乎合法，可能比我做的更好。然而，这里的目的是使用Java8特性来“玩”它。我对你的答案做了a+1，因为它真的很有趣，我喜欢它。不幸的是，它不能回答我的问题。我很乐意帮忙。很抱歉，我错过了你的意图。在Java8站点上，这仍然是一个有趣的问题。
public class DefaultPersonBuilder implements PersonBuilder {

    private String firstName;
    private String lastName;
    private String gender;

    @Override
    public PersonBuilder withFirstName(String firstName) {
        this.firstName = firstName;
        return this;
    }

    @Override
    public PersonBuilder withLastName(String lastName) {
        this.lastName = lastName;
        return this;
    }

    @Override
    public PersonBuilder withGender(String gender) {
        this.gender = gender;
        return this;
    }

    @Override
    public Person create() {
        // Check firstName Parameter
        if (firstName == null || firstName.isEmpty()) {
            throw new IllegalArgumentException("The firstName argument expect to not be null or empty");
        }

        [... your implementation using the fields]
    }
}

public Person parseLine(String line, String separator, PersonBuilder person) {
    String[] separedLine = line.split(separator);
    String firstName = separedLine[0];
    String lastName = separedLine[1];
    String gender = separedLine[2];
    return person.withFirstName(firstName).withLastName(lastName).withGender(gender).create();
}