Java中的枚举enum

public class EnumTest {
    enum RadioState {
        RADIO_OFF,         /* Radio explictly powered off (eg CFUN=0) */
        RADIO_UNAVAILABLE, /* Radio unavailable (eg, resetting or not booted) */
        SIM_NOT_READY,     /* Radio is on, but the SIM interface is not ready */
        SIM_LOCKED_OR_ABSENT,  /* SIM PIN locked, PUK required, network
                               personalization, or SIM absent */
        SIM_READY,         /* Radio is on and SIM interface is available */
        RUIM_NOT_READY,    /* Radio is on, but the RUIM interface is not ready */
        RUIM_READY,        /* Radio is on and the RUIM interface is available */
        RUIM_LOCKED_OR_ABSENT, /* RUIM PIN locked, PUK required, network
                                  personalization locked, or RUIM absent */
        NV_NOT_READY,      /* Radio is on, but the NV interface is not available */
        NV_READY;          /* Radio is on and the NV interface is available */

        public boolean isOn() /* and available...*/ {
            return this == SIM_NOT_READY
                    || this == SIM_LOCKED_OR_ABSENT
                    || this == SIM_READY
                    || this == RUIM_NOT_READY
                    || this == RUIM_READY
                    || this == RUIM_LOCKED_OR_ABSENT
                    || this == NV_NOT_READY
                    || this == NV_READY;
        }

        public boolean isAvailable() {
            return this != RADIO_UNAVAILABLE;
        }

        public boolean isSIMReady() {
            return this == SIM_READY;
        }

        public boolean isRUIMReady() {
            return this == RUIM_READY;
        }

        public boolean isNVReady() {
            return this == NV_READY;
        }

        public boolean isGsm() {
            return this == SIM_NOT_READY
                    || this == SIM_LOCKED_OR_ABSENT
                    || this == SIM_READY;
        }

        public boolean isCdma() {
            return this ==  RUIM_NOT_READY
                    || this == RUIM_READY
                    || this == RUIM_LOCKED_OR_ABSENT
                    || this == NV_NOT_READY
                    || this == NV_READY;
        }
    }

	public static void main(String[] args) {
		RadioState mRS = RadioState.RADIO_OFF;

		System.out.println("RadioState isOn: " + mRS.isOn());
		System.out.println("RadioState.RADIO_OFF: " + mRS.RADIO_OFF);
	}
}

1. RadioState枚举类就是class，而且是一个不可以被继承的final类。其枚举值(RADIO_OFF...)都是RadioState类型的静态常量，

2. 即然枚举类是class，当然在枚举类型中有构造器，方法和数据域。但是，枚举类的构造器有很大的不同： 

  (1) 构造器只是在构造枚举值的时候被调用。  

  (2) 构造器只能私有private，绝对不允许有public构造器。

3. 所有枚举类都继承了Enum的方法.

参考文章：http://www.javaeye.com/topic/477731