如何为实现接口的类创建一个Java构造函数

huangapple
go评论93阅读模式
英文:

How to make a Java constructor for a class that implements an interface

问题

我知道要使用一个接口，我需要将其实现为一个类。然而，我不理解如何为该类创建构造函数？我没有其他要添加到接口Classroom的方法或变量，我只需要为它创建一个构造函数，以便我可以使用它并创建一个Classroom对象。

当我尝试使用接口时，比如 Classroom classroom = new Classroom()，我知道这是错误的，但我的IDE会通过以下方式修复它：

  1. Classroom classroom = new Classroom() {
  2.     @Override
  3.     public Map<String, String> students() {
  4.         return null;
  5.     }
  7.     @Override
  8.     public String grade() {
  9.         return null;
  10.     }
  12.     @Override
  13.     public Optional<String> teacher() {
  14.         return Optional.empty();
  15.     }
  16. }

我不知道如何解释来自我的IDE的建议，我应该为students()、grade()等编写方法吗？我只需要使用我的自定义值为students、grade和teacher创建一个Classroom对象。

我是Java的新手。

英文:

I have an interface I need to use that looks similar to:

  1. public interface Classroom {
  2.     enum Grade {
  3.         Primary, Elementary
  4.     }
  6.     Map&lt;String, String&gt; students();
  8.     String grade();
  10.     Optional&lt;String&gt; teacher();
  11. }

I know in order to use an interface, I need to implement it as a class. However, I don't understand how to create the constructor for the class? I don't have any other methods or variables to add to the interface Classroom, I just need a constructor for it so I can use it and create a Classroom object.

  1. public class BiologyClassroom implements Classroom {
  2.     public BiologyClassroom(Map&lt;String, String&gt; students, String grade, Optional&lt;String&gt; teacher) {
  3.         // not sure what to put here?
  4.     }
  5. }

When I do try to use the interface by doing Classroom classroom = new Classroom() which I know is wrong, my IDE will fix it by by replacing it with:

  1. Classroom classroom = new Classroom() {
  2.             @Override
  3.             public Map&lt;String, String&gt; students() {
  4.                 return null;
  5.             }
  7.             @Override
  8.             public Grade grade() {
  9.                 return null;
  10.             }
  12.             @Override
  13.             public Optional&lt;String&gt; teacher() {
  14.                 return Optional.empty();
  15.             }
  16.         }

I don't know how to interpret this suggestion from my IDE, am I supposed to write methods for students(), grade() etc? I just need to make a Classroom object using my own values for students, grade and teacher.

I am new to Java.

答案1

得分: 0

你可以将接口中的方法实际上视为获取器（不以 "get" 开头），因此，如果你想避免重复太多代码，可以使用抽象类：

  1. public abstract class AbstractClassroom implements Classroom {
  2.     private final Map<String, String> students;
  3.     private final Grade grade;
  4.     private final Optional<String> teacher;
  6.     protected AbstractClassroom(Map<String, String> students, Grade grade, Optional<String> teacher) {
  7.         this.students = students;
  8.         this.grade = grade;
  9.         this.teacher = teacher;
  10.     }
  12.     @Override
  13.     public Map<String, String> students() {
  14.         return students;
  15.     }
  17.     @Override
  18.     public Grade grade() {
  19.         return grade;
  20.     }
  22.     @Override
  23.     public Optional<String> teacher() {
  24.         return teacher;
  25.     }
  26. }

然后，你可以按照以下方式编写你的 BiologyClassroom 类：

  1. public class BiologyClassroom extends AbstractClassroom {
  2.     public BiologyClassroom(Map<String, String> students, Grade grade, Optional<String> teacher) {
  3.         super(students, grade, teacher);
  4.     }
  5. }

你还可以考虑放弃接口，直接使用抽象类。

英文:

The methods in your interface are actually getters (that don't start with "get"), so if you want to avoid repeating too much code, you can use an abstract class:

  1. public abstract class AbstractClassroom implements Classroom {
  2.     private final Map&lt;String, String&gt; students;
  3.     private final Grade grade;
  4.     private final Optional&lt;String&gt; teacher;
  6.     protected AbstractClassroom(Map&lt;String, String&gt; students, Grade grade, Optional&lt;String&gt; teacher) {
  7.         this.students = students;
  8.         this.grade = grade;
  9.         this.teacher = teacher;
  10.     }
  12.     @Override
  13.     public Map&lt;String, String&gt; students() {
  14.         return students;
  15.     }
  17.     @Override
  18.     public Grade grade() {
  19.         return grade;
  20.     }
  22.     @Override
  23.     public Optional&lt;String&gt; teacher() {
  24.         return teacher;
  25.     }
  26. }

You can then write your class BiologyClassroom as follows:

  1. public class BiologyClassroom extends AbstractClassroom {
  2.     public BiologyClassroom(Map&lt;String, String&gt; students, String grade, Optional&lt;String&gt; teacher) {
  3.         super(students, grade, teacher);
  4.     }
  5. }

You can also consider dropping the interface and use the abstract class instead.

答案2

得分: 0

在你的 interface 中，你已经将 students、grades 和 teacher 声明为方法。我认为你打算将它们用作 variables。

只需使用基本的继承；没有必要特别使用 interface。

  1. class Classroom {
  2.     enum Grade {
  3.         Primary, Elementary
  4.     }
  6.     Map&lt;String, String&gt; students;
  7.     String grade;
  8.     Optional&lt;String&gt; teacher;
  10.     public Classroom(Map&lt;String, String&gt; students, String grade, Optional&lt;String&gt; teacher) {
  11.         this.students = students;
  12.         this.grade = grade;
  13.         this.teacher = teacher;
  14.     }
  15. }
  1. class BiologyClassroom extends Classroom {
  2.     public BiologyClassroom(Map&lt;String, String&gt; students, String grade, Optional&lt;String&gt; teacher) {
  3.         super(students, grade, teacher);
  4.     }
  5. }

这是关于继承的 Java 教程链接。Inheritance (The Java&trade; Tutorials &gt; Learning the Java Language &gt; Interfaces and Inheritance)。

英文:

In your interface you have declared students, grades, and teacher as methods.
I believe you are intending to use them as variables.

Just use basic inheritance; there is no need for an interface, per se.

  1. class Classroom {
  2.     enum Grade {
  3.         Primary, Elementary
  4.     }
  6.     Map&lt;String, String&gt; students;
  7.     String grade;
  8.     Optional&lt;String&gt; teacher;
  10.     public Classroom(Map&lt;String, String&gt; students, String grade, Optional&lt;String&gt; teacher) {
  11.         this.students = students;
  12.         this.grade = grade;
  13.         this.teacher = teacher;
  14.     }
  15. }
  1. class BiologyClassroom extends Classroom {
  2.     public BiologyClassroom(Map&lt;String, String&gt; students, String grade, Optional&lt;String&gt; teacher) {
  3.         super(students, grade, teacher);
  4.     }
  5. }

Here is the Java tutorial on inheritance.
Inheritance (The Java&trade; Tutorials &gt; Learning the Java Language &gt; Interfaces and Inheritance).

huangapple
  • 本文由 发表于 2023年7月10日 14:32:04
  • 转载请务必保留本文链接：https://go.coder-hub.com/76651175.html
  • java
  • oop
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定