java枚举之简要

public class EnumTest {

public static void main(String[] args) {

WeekDay1 weekDay = WeekDay1.MON;
//System.out.println(weekDay.nextDay().toString());

WeekDay weekDay2 = WeekDay.SAT;
System.out.println(weekDay2); //SAT
System.out.println(weekDay2.ordinal()); //SAT排序 为6
System.out.println(weekDay2.valueOf("SUN").toString());//SUN 返回一个字符串表现形式
System.out.println(weekDay2.values().length);//values()表示一个数组
}

//1.定义一个枚举类
public enum WeekDay{

SUN,MON,TUE,WED,THI,FRI,SAT;
//所有的方法必须位于所有的元素之后
//枚举类的构造方法必须是私有的
private  WeekDay(){
System.out.println("first");
}
//如果要调用带有参数的构造器，可以这样
//SUN(1),MON,TUE,WED,THI,FRI,SAT;
private WeekDay(int day){
System.out.println("second");
}
}

//交通灯
public enum TrafficLamp{

RED(30){
//红灯的下一个是绿灯
public  TrafficLamp nextLamp(){

return GREEN;
}
},
GREEN(45){
//绿灯的下一个是黄灯
public  TrafficLamp nextLamp(){

return YELLOW;
}
},
YELLOW(5){
//黄灯的下一个是红灯
public  TrafficLamp nextLamp(){

return RED;
}
};
public abstract TrafficLamp nextLamp();
//指定的是交通灯亮的长度
private int time;
private TrafficLamp(int time){

this.time = time;
}
}
}
打印结果为:
second
second
first
first
first
first
first
SAT
6
SUN
7
相当于枚举类的每个元素都要被初始化构造