本文內容出自於《JAVA程式設計思想》，有興趣的讀者可自行翻閱

values() 的神祕之處

values() 是由編譯器新增的static方法，除此之外，還有valueOf()方法，與Enum類中的valueOf()方法不同的是引數的個數不同，如下是程式碼展示。

enum Explore{HERE,THERE}
public class test01 {
    public static Set<String> analyze(Class<?> enumClass){
        System.out.println("------Analyzing " + enumClass +"------");
        System.out.println("Interfaces:");
        for (Type t: enumClass.getGenericInterfaces()) {
            System.out.println(t+"---");
        }
        System.out.println("Base: "+enumClass.getSuperclass());
        System.out.println("Methods: ");
        Set<String> methods = new TreeSet<String>();
        for (Method m:enumClass.getMethods()
             ) {
            methods.add(m.getName());
        }
        System.out.println(methods);
        return methods;
    }

    public static void main(String[] args) {
        Set<String> exploreMethods = analyze(Explore.class);
        Set<String> enummMethods = analyze(Enum.class);
        System.out.println("Explore.containsAll(Enum)?"+
        exploreMethods.containsAll(enummMethods));
        System.out.println("Explore.containsAll(Enum)?"+
                exploreMethods.removeAll(enummMethods));
        System.out.println(exploreMethods);

    }
}
/**
輸出
------Analyzing class Explore------
Interfaces:
Base: class java.lang.Enum
Methods: 
[compareTo, equals, getClass, getDeclaringClass, hashCode, name, notify, notifyAll, ordinal, toString, valueOf, values, wait]
------Analyzing class java.lang.Enum------
Interfaces:
java.lang.Comparable<E>---
interface java.io.Serializable---
Base: class java.lang.Object
Methods: 
[compareTo, equals, getClass, getDeclaringClass, hashCode, name, notify, notifyAll, ordinal, toString, valueOf, wait]
Explore.containsAll(Enum)?true
Explore.containsAll(Enum)?true
[values]
*/
 

隨機選取的簡單示例

enum Activity{SITTING,LYING,STANDING,HOPPING,
RUNNING,DODGING,JUMPING,FALLING,FLYING}
public class RandomTest {
    public static void main(String[] args) {
        for (int i = 0;i<20;i++){
            System.out.print(Enums.random(Activity.class)+" ");
        }
    }
}

介面組織的列舉

public enum SecurityCategory {
    STOCK(Security.Stock.class),BOND(Security.Bond.class);
    Security[] values;
    SecurityCategory(Class<? extends Security> kind){
        values = kind.getEnumConstants();
    }

    interface Security{
        enum Stock implements Security{SHORT,LONG,MARGIN}
        enum Bond implements Security{MUNICIPAL,JUNK}
    }

    public Security randomSelection(){
        return Enums.random(values);
    }

    public static void main(String[] args) {
        for(int i=0;i<10;i++){
            SecurityCategory category = Enums.random(SecurityCategory.class);

            System.out.println(category+": "+category.randomSelection()+"|");
        }
    }
}
/**
output:BOND: MUNICIPAL|BOND: MUNICIPAL|STOCK: MARGIN|STOCK: MARGIN|BOND: JUNK|STOCK: SHORT|STOCK: LONG|STOCK: LONG|BOND: MUNICIPAL|BOND: JUNK|
*/
 

總結

列舉這一特性非常適合用來表示特定的有限屬性，除了上面所述之外，還有EnumSet，EnumMap，常量方法，需要使用的時候可再查閱資料