Java 一个数据类型只能有2个值吗？或者只能有n个值？

这个问题没有多大意义，让我解释一下。 例如，我想要一门课

package code;

public class Person {

String Name; //a person has a name
SomeKindOfDatattype gender; //A person has a gender
//i want only 2 possible values of gender that is male or female
}

---

请简要说明

使用枚举满足此需求。在里面，您可以列出所有的默认值

boolean male;

只允许对或错

枚举还允许值

null

不真实的值。

您可以使用枚举

 public enum Gender{ MALE,FEMALE } 

---

数据类型将为性别

如果您的类型必须仅具有某些值，请使用枚举：

enum Gender {
    MALE, 
    FEMALE
} 

public class Person {
    String Name;

    Gender gender;
}

您可以定义包含“男性”和“女性”值的枚举“性别” （可以嵌入到类中）

---

可以通过

性别调用。男性

您可以使用

枚举

如下

enum Gender {
    MALE, FEMALE;
}

下面是一些如何定义和使用它的示例。

---

您可以使用枚举来执行所需操作

在这里，您是一个如何继续的示例

Person.java

public class Person{

  private String name; 
  Gender gender; 

  public Person(String name, Gender gender){
    this.name = name;
    this.gender = gender;
 }

  public void display(){

    System.out.println("I'm " + name + " and I'm " + gender);
  }
}

public enum Gender{ Male, Female}

public class TestPerson{

  public static void main(String[] args){

    String name = "Alan";
    Gender gender = Gender.Male;
    Person p = new Person("Alan", gender);
    p.display();
  }
}

Gender.java

public class Person{

  private String name; 
  Gender gender; 

  public Person(String name, Gender gender){
    this.name = name;
    this.gender = gender;
 }

  public void display(){

    System.out.println("I'm " + name + " and I'm " + gender);
  }
}

public enum Gender{ Male, Female}

public class TestPerson{

  public static void main(String[] args){

    String name = "Alan";
    Gender gender = Gender.Male;
    Person p = new Person("Alan", gender);
    p.display();
  }
}

下面是测试代码

TestPerson.java

public class Person{

  private String name; 
  Gender gender; 

  public Person(String name, Gender gender){
    this.name = name;
    this.gender = gender;
 }

  public void display(){

    System.out.println("I'm " + name + " and I'm " + gender);
  }
}

public enum Gender{ Male, Female}

public class TestPerson{

  public static void main(String[] args){

    String name = "Alan";
    Gender gender = Gender.Male;
    Person p = new Person("Alan", gender);
    p.display();
  }
}

---

代码没有提到包名。我假设以上所有代码都在同一个包中。您可以根据需要指定包名。

枚举类：

public enum Gender {
    MALE, FEMALE;
}

public class Person {

    private String name;
    private Gender gender;

    public Person(String name, Gender gender) {
        this.name = name;
        this.gender = gender;
    }

    @Override
    public String toString() {
        return name + " is " + gender;
    }

}

public class Main {

    public static void main(String[] args) {

        Person person = new Person("Charles", Gender.MALE);
        Person person1 = new Person("Kelly", Gender.FEMALE);

        System.out.println(person.toString());
        System.out.println(person1.toString());

    }
}

Charles is MALE
Kelly is FEMALE

人员类别：

public enum Gender {
    MALE, FEMALE;
}

public class Person {

    private String name;
    private Gender gender;

    public Person(String name, Gender gender) {
        this.name = name;
        this.gender = gender;
    }

    @Override
    public String toString() {
        return name + " is " + gender;
    }

}

public class Main {

    public static void main(String[] args) {

        Person person = new Person("Charles", Gender.MALE);
        Person person1 = new Person("Kelly", Gender.FEMALE);

        System.out.println(person.toString());
        System.out.println(person1.toString());

    }
}

Charles is MALE
Kelly is FEMALE

主要应用程序：

public enum Gender {
    MALE, FEMALE;
}

public class Person {

    private String name;
    private Gender gender;

    public Person(String name, Gender gender) {
        this.name = name;
        this.gender = gender;
    }

    @Override
    public String toString() {
        return name + " is " + gender;
    }

}

public class Main {

    public static void main(String[] args) {

        Person person = new Person("Charles", Gender.MALE);
        Person person1 = new Person("Kelly", Gender.FEMALE);

        System.out.println(person.toString());
        System.out.println(person1.toString());

    }
}

Charles is MALE
Kelly is FEMALE

输出：

public enum Gender {
    MALE, FEMALE;
}

public class Person {

    private String name;
    private Gender gender;

    public Person(String name, Gender gender) {
        this.name = name;
        this.gender = gender;
    }

    @Override
    public String toString() {
        return name + " is " + gender;
    }

}

public class Main {

    public static void main(String[] args) {

        Person person = new Person("Charles", Gender.MALE);
        Person person1 = new Person("Kelly", Gender.FEMALE);

        System.out.println(person.toString());
        System.out.println(person1.toString());

    }
}

Charles is MALE
Kelly is FEMALE

---

您可以向构造函数/方法添加验证，以确保只接受特定值。另一个想法是使用

枚举

，这将允许您定义常量，如

男性

和

女性

。你可以在这里找到

enum

教程：Theraphrodites可能有两种性别。天哪，这么简单的问题有8个答案@叶海亚和所有追求名誉的人。只是为了好玩，我想增加500英镑的赏金，看看他们是如何互相残杀的；哈哈，这会很有趣的！谢谢大家。我是一个12岁的孩子，想学java。你们在这方面一定很专业！如果这个问题让你畏缩，我很抱歉。enum工作的人会讨厌的