blocks|key|1086251|text|可以，停那儿吧。它看起来像这样：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1086252|public+enum+Animal+{
++ELEPHANT(false),
++GIRAFFE(false),
++TURTLE(false),
++SNAKE(false),
++FROG(true);

++private+final+boolean+isAmphibian;

++Animal(boolean+isAmphibian)+{
++++this.isAmphibian+=+isAmphibian;
++}

++public+boolean+isAmphibian()+{
++++return+this.isAmphibian;
++}
}|code-block|syntax|javascript|1086253|那么你可以这样称呼它：|1086254|Animal.ELEPHANT.isAmphibian()|offset|length|style|CODE|1086255|entityMap^0|0|0|0|0|T|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|T|8|@$K|U|L|V|M|N]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

Yes, you can. It would look like this:

<pre><code>public enum Animal {
 ELEPHANT(false),
 GIRAFFE(false),
 TURTLE(false),
 SNAKE(false),
 FROG(true);

 private final boolean isAmphibian;

 Animal(boolean isAmphibian) {
 this.isAmphibian = isAmphibian;
 }

 public boolean isAmphibian() {
 return this.isAmphibian;
 }
}
</code></pre>

Then you would call it like:

<code>Animal.ELEPHANT.isAmphibian()</code>

blocks|key|1086286|text|是的，Enum是Java中的一个类：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1086287|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;+}
}|code-block|syntax|javascript|1086288|但在您的真实系统中，我也会将其设为Enum，因为有一组固定的动物类型。|1086289|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...
}|1086290|还要注意，将任何实例变量设为final也很重要。|offset|length|style|CODE|1086291|您可以在Java+Language+Specification中找到有关它的更多详细信息。|1086292|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/javase/specs/jls/se11/html/jls-8.html#jls-8.9.2^0|0|0|0|0|E|5|0|4|R|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|14|8|@$M|15|N|16|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|17|8|@]|9|@$M|18|N|19|1|1A]]|A|$]]|$1|S|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

<h2>Yes Enum is a class in Java:</h2>
<pre><code>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; }
}
</code></pre>
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.
<pre><code>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...
}
</code></pre>
Also note that it is important to make any instance variable <code>final</code> as well.
You can find more details about it in the <a href="https://docs.oracle.com/javase/specs/jls/se11/html/jls-8.html#jls-8.9.2" rel="noreferrer">Java Language Specification</a>.

blocks|key|1301539|text|除了使用上面向枚举类型添加字段的技术之外，您还可以使用基于纯方法的方法和多态性。这是更多的"OOP风格“，但我不会说它一定更好。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1301540|不幸的是，您可能(参见下面的注释)需要定义一个接口：|1301541|public+interface+AnimalTraits+{
++++default+boolean+isAmphibian()+++{+return+false;+};
++++default+boolean+isReptile()+++++{+return+false;+};
++++default+boolean+isMammal()++++++{+return+false;+};
}|code-block|syntax|javascript|1301542|但是，您可以在每个枚举元素中实现该接口：|1301543|public+enum+Animal+implements+AnimalTraits+{

+++++ELEPHANT+++{+@Override+public+boolean+isMammal()++++{+return+true;+}+},
+++++GIRAFFE++++{+@Override+public+boolean+isMammal()++++{+return+true;+}+},
+++++TURTLE+++++{+@Override+public+boolean+isReptile()+++{+return+true;+}+},
+++++SNAKE++++++{+@Override+public+boolean+isReptile()+++{+return+true;+}+},
+++++FROG+++++++{+@Override+public+boolean+isAmphibian()+{+return+true;+}+}
}|1301544|请注意，我在接口中使用默认实现，以减少在枚举中所需的打字量。|1301545|关于接口的必要性:我尝试将接口中的方法作为抽象方法添加到枚举的顶部，Eclipse似乎允许这样做，并坚持在枚举元素中实现，但随后无法正确编译这些方法。因此，它看起来应该可以在没有接口的情况下实现，但可能还没有在编译器中实现。|1301546|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

As well as using the techniques above which add a field to the enumerated type you can also use a pure method based approach and polymorphism. This is more "OOP style" but I would not say it is necessarily better.

Unfortunately, you may (see the comment below) need to define an interface:

<pre><code>public interface AnimalTraits {
 default boolean isAmphibian() { return false; };
 default boolean isReptile() { return false; };
 default boolean isMammal() { return false; };
}
</code></pre>

But then you can them implement the interface in each of your enumeration elements:

<pre><code>public enum Animal implements AnimalTraits {

 ELEPHANT { @Override public boolean isMammal() { return true; } },
 GIRAFFE { @Override public boolean isMammal() { return true; } },
 TURTLE { @Override public boolean isReptile() { return true; } },
 SNAKE { @Override public boolean isReptile() { return true; } },
 FROG { @Override public boolean isAmphibian() { return true; } }
}
</code></pre>

Note that I use default implementations in the interface to cut down on the amount of typing you need in the enum.

Regarding the necessity of the interface: I tried adding the methods in the interface as abstract methods at the top of the enum and Eclipse seemed to allow it and insisted on implementations in the enum elements, but then failed to compile those properly. So it looks like it ought to be possible without an interface, but perhaps it is not yet implemented in the compiler.

blocks|key|1086456|text|我还有另外一个选择：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1086457|public+enum+Animal+{
++++ELEPHANT+{
++++++++@Override
++++++++boolean+isMammal()+{
++++++++++++return+true;
++++++++};
++++++++@Override
++++++++boolean+isReptile()+{
++++++++++++return+false;
++++++++}
++++},
++++SNAKE+{
++++++++@Override
++++++++boolean+isMammal()+{
++++++++++++return+false;
++++++++};
++++++++@Override
++++++++boolean+isReptile()+{
++++++++++++return+true;
++++++++}
++++};

++++abstract+boolean+isMammal();
++++abstract+boolean+isReptile();
}|code-block|syntax|javascript|1086458|不需要外部接口，我非常确定(没有测试)它也可以在Java7上工作。|1086459|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I have an other option:

<pre><code>public enum Animal {
 ELEPHANT {
 @Override
 boolean isMammal() {
 return true;
 };
 @Override
 boolean isReptile() {
 return false;
 }
 },
 SNAKE {
 @Override
 boolean isMammal() {
 return false;
 };
 @Override
 boolean isReptile() {
 return true;
 }
 };

 abstract boolean isMammal();
 abstract boolean isReptile();
}
</code></pre>

No need of external Interface and I am quite sure (did not test) it works also on Java7.

I have an enum, which looks like

<pre><code>public enum Animal {
 ELEPHANT,
 GIRAFFE,
 TURTLE,
 SNAKE,
 FROG
}
</code></pre>

and I want to do something like

<pre><code>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
</code></pre>

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?

Can I add a function to enums in Java?

我有一个枚举，它看起来像public enum Animal {  ELEPHANT,  GIRAFFE,  TURTLE,  SNAKE,  FROG}我想做一些像这样的事情Animal frog = Animal.FROG;Animal snake = Animal.SNAKE;boolean isFrogAmph...

问我可以向Java中的枚举添加函数吗？
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