Java 枚举和具有私有构造函数的类有什么区别 [复制]

Java中的枚举和具有私有构造函数的类有一些区别。本文将介绍这两种概念，并通过案例代码来说明它们的不同之处。

java
enum Weekday {
  MONDAY,
  TUESDAY,
  WEDNESDAY,
  THURSDAY,
  FRIDAY,
  SATURDAY,
  SUNDAY
}

java
enum Weekday {
  MONDAY("Monday"),
  TUESDAY("Tuesday"),
  // ...
  
  private String name;
  
  private Weekday(String name) {
    this.name = name;
  }
  
  public String getName() {
    return name;
  }
}

java
class Singleton {
  private static Singleton instance;
  
  private Singleton() {
    // 私有构造函数
  }
  
  public static Singleton getInstance() {
    if (instance == null) {
      instance = new Singleton();
    }
    return instance;
  }
}

java
enum Weekday {
  MONDAY,
  TUESDAY,
  WEDNESDAY,
  THURSDAY,
  FRIDAY,
  SATURDAY,
  SUNDAY
}
class Singleton {
  private static Singleton instance;
  
  private Singleton() {
    // 私有构造函数
  }
  
  public static Singleton getInstance() {
    if (instance == null) {
      instance = new Singleton();
    }
    return instance;
  }
}
public class Main {
  public static void main(String[] args) {
    // 枚举使用示例
    Weekday weekday = Weekday.MONDAY;
    System.out.println(weekday);
    
    // 单例模式使用示例
    Singleton singleton1 = Singleton.getInstance();
    Singleton singleton2 = Singleton.getInstance();
    System.out.println(singleton1 == singleton2);  // 输出true
  }
}