Can I add a function to enums in Java?

enums, function, java

Solution

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; }
}

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...
}

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

You can find more details about it in the Java Language Specification.

Problem

I have an enum, which looks like ``` public enum Animal { ELEPHANT, GIRAFFE, TURTLE, SNAKE, FROG } ``` and I want to do something like ``` 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 ``` 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?

Original source

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