除了不能继承enum之外，可将其看做一个常规类。甚至能够有main方法。
注意：必须先定义enum实例。实例的最后有一个分号。
以下是一个样例：返回对实例自身的描写叙述，而非默认的toString返回枚举实例的名字。
public enum Color {
RED("红色", 1), GREEN("绿色", 2), BLANK("白色", 3), YELLO("黄色", 4);
// 成员变量
private String name;
private int index;
// 构造方法
private Color(String name, int index) {
this.name = name;
this.index = index;
}
public static String getName(int index) {
//利用了枚举自身的values()方法；
for (Color c : Color.values()) {
if (c.getIndex() == index) {
return c.name;
}
}
return null;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
重要性在于：能够调用对应枚举成员的方法来生成对应的对象，比方以下的OFType，能够这样使用：
OFType t = OFType.HELLO;
t.newInstance();
以下是Floodlight controller中相关知识点的体现
public enum OFType {
//这里自己定义构造方法。有三个參数
HELLO (0, OFHello.class, new Instantiable<OFMessage>() {
@Override
public OFMessage instantiate() {
return new OFHello();
}}),
ERROR (1, OFError.class, new Instantiable<OFMessage>() {
@Override
public OFMessage instantiate() {
return new OFError();
}}),
PACKET_IN (10, OFPacketIn.class, new Instantiable<OFMessage>() {
@Override
public OFMessage instantiate() {
return new OFPacketIn();
}}),
PACKET_OUT (13, OFPacketOut.class, new Instantiable<OFMessage>() {
@Override
public OFMessage instantiate() {
return new OFPacketOut();
}}),
FLOW_MOD (14, OFFlowMod.class, new Instantiable<OFMessage>() {
@Override
public OFMessage instantiate() {
return new OFFlowMod();
}});
static OFType[] mapping;
//每一个消息类型，都须要相应的详细实现类
protected Class<? extends OFMessage> clazz;
//每一个消息类的无參构造器
protected Constructor<? extends OFMessage> constructor;
//接口 Instantiable 有一个初始化实例的方法。创建详细的OFMessage
protected Instantiable<OFMessage> instantiable;
//消息类型的值
protected byte type;
/**构造方法
* Store some information about the OpenFlow type, including wire protocol
* type number, length, and derived class
*
* @param type Wire protocol number associated with this OFType
* @param requestClass The Java class corresponding to this type of OpenFlow message
* @param instantiator An Instantiator<OFMessage> implementation that creates an
* instance of the specified OFMessage
*/
OFType(int type, Class<? extends OFMessage> clazz, Instantiable<OFMessage> instantiator) {
this.type = (byte) type;
this.clazz = clazz;
this.instantiable = instantiator;
try {
this.constructor = clazz.getConstructor(new Class[]{});
} catch (Exception e) {
throw new RuntimeException("Failure getting constructor for class: " + clazz, e);
}
OFType.addMapping(this.type, this); //值到枚举类的映射
}
/**
* Adds a mapping from type value to OFType enum
*
* @param i OpenFlow wire protocol type
* @param t type
*/
static public void addMapping(byte i, OFType t) {
if (mapping == null)
mapping = new OFType[32];
OFType.mapping[i] = t;
}
/**
* Remove a mapping from type value to OFType enum
*
* @param i OpenFlow wire protocol type
*/
static public void removeMapping(byte i) {
OFType.mapping[i] = null;
}
/**
* Given a wire protocol OpenFlow type number, return the OFType associated
* with it
*
* @param i wire protocol number
* @return OFType enum type
*/
static public OFType valueOf(Byte i) {
return OFType.mapping[i];
}
/**
* @return Returns the wire protocol value corresponding to this OFType
*/
public byte getTypeValue() {
return this.type;
}
/**
* @return return the OFMessage subclass corresponding to this OFType
*/
public Class<? extends OFMessage> toClass() {
return clazz;
}
/**
* Returns the no-argument Constructor of the implementation class for
* this OFType
* @return the constructor
*/
public Constructor<?
extends OFMessage> getConstructor() {
return constructor;
}
/**
* Returns a new instance of the OFMessage represented by this OFType
* @return the new object
*/
public OFMessage newInstance() {
return instantiable.instantiate();
}
/**
* @return the instantiable
*/
public Instantiable<OFMessage> getInstantiable() {
return instantiable;
}
/**
* @param instantiable the instantiable to set
*/
public void setInstantiable(Instantiable<OFMessage> instantiable) {
this.instantiable = instantiable;
}
}
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