我可以在Java中的枚举中添加一个函数吗？ [英] Can I add a function to enums in Java?

问题描述

我有一个枚举，看起来像

I have an enum, which looks like

public enum Animal {
  ELEPHANT,
  GIRAFFE,
  TURTLE,
  SNAKE,
  FROG
}

我想做一些像

Animal frog = Animal.FROG;
Animal snake = Animal.SNAKE;

boolean isFrogAmphibian = frog.isAmphibian(); //true
boolean isSnakeAmphibian = snake.isAmphibian(); //false

boolean isFrogReptile = frog.isReptile(); //false
boolean isSnakeReptile = snake.isReptile(); //true

boolean isFrogMammal = frog.isMammal(); //false
boolean isSnakeMammal = snake.isMammal(); //false

我简化了教学目的的例子，但这对我来说真的很有用现实生活中的例子可以在Java中执行吗？

I simplified the example for didactic purposes, but this would be really useful to me for my real life example. Can I do it in Java?

推荐答案

是枚举是Java中的一个类：

Yes Enum is a class in Java:

public enum Animal 
{
  ELEPHANT(true),
  GIRAFFE(true),
  TURTLE(false),
  SNAKE(false),
  FROG(false);

  private final boolean mammal; 
  private Animal(final boolean mammal) { this.mammal = mammal; }
  public boolean isMammal() { return this.mammal; }
}

但在你的情况下，一个真正的系统我会使一个枚举为好的，因为有一组固定的动物。

but in your case for a real system I would make that an Enum as well since there is a fixed set of types of animals.

public enum Type
{
  AMPHIBIAN,
  MAMMAL,
  REPTILE,
  BIRD
}

public enum Animal 
{
  ELEPHANT(Type.MAMMAL),
  GIRAFFE(Type.MAMMAL),
  TURTLE(Type.REPTILE),
  SNAKE(Type.REPTILE),
  FROG(Type.AMPHIBIAN);

  private final Type type; 
  private Animal(final Type type) { this.type = type; }
  public boolean isMammal() { return this.type == Type.MAMMAL; }
  public boolean isAmphibian() { return this.type == Type.AMPHIBIAN; }
  public boolean isReptile() { return this.type == Type.REPTILE; }
  // etc...
}

另请注意，重要的是使任何实例变量 final 。

Also note that it is important to make any instance variable final as well.

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